Commit Graph

449 Commits

Author SHA1 Message Date
Jeff Moyer
c10b61f091 cfq: Don't allow queue merges for queues that have no process references
Hi,

A user reported a kernel bug when running a particular program that did
the following:

created 32 threads
- each thread took a mutex, grabbed a global offset, added a buffer size
  to that offset, released the lock
- read from the given offset in the file
- created a new thread to do the same
- exited

The result is that cfq's close cooperator logic would trigger, as the
threads were issuing I/O within the mean seek distance of one another.
This workload managed to routinely trigger a use after free bug when
walking the list of merge candidates for a particular cfqq
(cfqq->new_cfqq).  The logic used for merging queues looks like this:

static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
{
	int process_refs, new_process_refs;
	struct cfq_queue *__cfqq;

	/* Avoid a circular list and skip interim queue merges */
	while ((__cfqq = new_cfqq->new_cfqq)) {
		if (__cfqq == cfqq)
			return;
		new_cfqq = __cfqq;
	}

	process_refs = cfqq_process_refs(cfqq);
	/*
	 * If the process for the cfqq has gone away, there is no
	 * sense in merging the queues.
	 */
	if (process_refs == 0)
		return;

	/*
	 * Merge in the direction of the lesser amount of work.
	 */
	new_process_refs = cfqq_process_refs(new_cfqq);
	if (new_process_refs >= process_refs) {
		cfqq->new_cfqq = new_cfqq;
		atomic_add(process_refs, &new_cfqq->ref);
	} else {
		new_cfqq->new_cfqq = cfqq;
		atomic_add(new_process_refs, &cfqq->ref);
	}
}

When a merge candidate is found, we add the process references for the
queue with less references to the queue with more.  The actual merging
of queues happens when a new request is issued for a given cfqq.  In the
case of the test program, it only does a single pread call to read in
1MB, so the actual merge never happens.

Normally, this is fine, as when the queue exits, we simply drop the
references we took on the other cfqqs in the merge chain:

	/*
	 * If this queue was scheduled to merge with another queue, be
	 * sure to drop the reference taken on that queue (and others in
	 * the merge chain).  See cfq_setup_merge and cfq_merge_cfqqs.
	 */
	__cfqq = cfqq->new_cfqq;
	while (__cfqq) {
		if (__cfqq == cfqq) {
			WARN(1, "cfqq->new_cfqq loop detected\n");
			break;
		}
		next = __cfqq->new_cfqq;
		cfq_put_queue(__cfqq);
		__cfqq = next;
	}

However, there is a hole in this logic.  Consider the following (and
keep in mind that each I/O keeps a reference to the cfqq):

q1->new_cfqq = q2   // q2 now has 2 process references
q3->new_cfqq = q2   // q2 now has 3 process references

// the process associated with q2 exits
// q2 now has 2 process references

// queue 1 exits, drops its reference on q2
// q2 now has 1 process reference

// q3 exits, so has 0 process references, and hence drops its references
// to q2, which leaves q2 also with 0 process references

q4 comes along and wants to merge with q3

q3->new_cfqq still points at q2!  We follow that link and end up at an
already freed cfqq.

So, the fix is to not follow a merge chain if the top-most queue does
not have a process reference, otherwise any queue in the chain could be
already freed.  I also changed the logic to disallow merging with a
queue that does not have any process references.  Previously, we did
this check for one of the merge candidates, but not the other.  That
doesn't really make sense.

Without the attached patch, my system would BUG within a couple of
seconds of running the reproducer program.  With the patch applied, my
system ran the program for over an hour without issues.

This addresses the following bugzilla:
    https://bugzilla.kernel.org/show_bug.cgi?id=16217

Thanks a ton to Phil Carns for providing the bug report and an excellent
reproducer.

[ Note for stable: this applies to 2.6.32/33/34 ].

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Reported-by: Phil Carns <carns@mcs.anl.gov>
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2010-06-17 20:17:35 +02:00
Shaohua Li
d02a2c077f cfq-iosched: fix an oops caused by slab leak
I got below oops when unloading cfq-iosched. Considering scenario:
queue A merge to B, C merge to D and B will be merged to D. Before B is merged
to D, we do split B. We should put B's reference for D.

[  807.768536] =============================================================================
[  807.768539] BUG cfq_queue: Objects remaining on kmem_cache_close()
[  807.768541] -----------------------------------------------------------------------------
[  807.768543]
[  807.768546] INFO: Slab 0xffffea0003e6b4e0 objects=26 used=1 fp=0xffff88011d584fd8 flags=0x200000000004082
[  807.768550] Pid: 5946, comm: rmmod Tainted: G        W   2.6.34-07097-gf4b87de-dirty #724
[  807.768552] Call Trace:
[  807.768560]  [<ffffffff81104e8d>] slab_err+0x8f/0x9d
[  807.768564]  [<ffffffff811059e1>] ? flush_cpu_slab+0x0/0x93
[  807.768569]  [<ffffffff8164be52>] ? add_preempt_count+0xe/0xca
[  807.768572]  [<ffffffff8164bd9c>] ? sub_preempt_count+0xe/0xb6
[  807.768577]  [<ffffffff81648871>] ? _raw_spin_unlock+0x15/0x30
[  807.768580]  [<ffffffff8164bd9c>] ? sub_preempt_count+0xe/0xb6
[  807.768584]  [<ffffffff811061bc>] list_slab_objects+0x9b/0x19f
[  807.768588]  [<ffffffff8164bf0a>] ? add_preempt_count+0xc6/0xca
[  807.768591]  [<ffffffff81109e27>] kmem_cache_destroy+0x13f/0x21d
[  807.768597]  [<ffffffffa000ff13>] cfq_slab_kill+0x1a/0x43 [cfq_iosched]
[  807.768601]  [<ffffffffa000ffcf>] cfq_exit+0x93/0x9e [cfq_iosched]
[  807.768606]  [<ffffffff810973a2>] sys_delete_module+0x1b1/0x219
[  807.768612]  [<ffffffff8102fb5b>] system_call_fastpath+0x16/0x1b
[  807.768618] INFO: Object 0xffff88011d584618 @offset=1560
[  807.768622] INFO: Allocated in cfq_get_queue+0x11e/0x274 [cfq_iosched] age=7173 cpu=1 pid=5496
[  807.768626] =============================================================================

Cc: stable@kernel.org
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-25 10:17:26 +02:00
Konstantin Khlebnikov
80b15c7389 cfq-iosched: compact io_context radix_tree
Use small consequent indexes as radix tree keys instead of sparse cfqd address.

This change will reduce radix tree depth from 11 (6 for 32-bit hosts)
to 1 if host have <=64 disks under cfq control, or to 0 if there only one disk.
So, this patch save 10*560 bytes for each process (5*296 for 32-bit hosts)

For each cfqd allocate cic index from ida.
To unlink dead cic from tree without cfqd access store index into ->key.
(bit 0 -- dead mark, bits 1..30 -- index: ida produce id in range 0..2^31-1)

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-24 09:06:59 +02:00
Konstantin Khlebnikov
bca4b914b5 cfq-iosched: remove dead_key from cfq_io_context
Remove ->dead_key field from cfq_io_context to shrink its size to 128 bytes.
(64 bytes for 32-bit hosts)

Use lower bit in ->key as dead-mark, instead of moving key to separate field.
After this for dead cfq_io_context we got cic->key != cfqd automatically.
Thus, io_context's last-hit cache should work without changing.

Now to check ->key for non-dead state compare it with cfqd,
instead of checking ->key for non-null value as it was before.

Plus remove obsolete race protection in cfq_cic_lookup.
This race gone after v2.6.24-1728-g4ac845a

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-24 09:06:59 +02:00
Jens Axboe
ee9a3607fb Merge branch 'master' into for-2.6.35
Conflicts:
	fs/ext3/fsync.c

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-21 21:27:26 +02:00
Paul E. McKenney
f1ac2502e1 block: remove all rcu head initializations
Remove all rcu head inits. We don't care about the RCU head state before passing
it to call_rcu() anyway. Only leave the "on_stack" variants so debugobjects can
keep track of objects on stack.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-21 20:01:02 +02:00
Vivek Goyal
dcf097b247 blk-cgroup: Fix RCU correctness warning in cfq_init_queue()
It is necessary to be in an RCU read-side critical section when invoking
css_id(), so this patch adds one to blkiocg_add_blkio_group().  This is
actually a false positive, because this is called at initialization time
and hence always refers to the root cgroup, which cannot go away.

[  103.790505] ===================================================
[  103.790509] [ INFO: suspicious rcu_dereference_check() usage. ]
[  103.790511] ---------------------------------------------------
[  103.790514] kernel/cgroup.c:4432 invoked rcu_dereference_check() without protection!
[  103.790517]
[  103.790517] other info that might help us debug this:
[  103.790519]
[  103.790521]
[  103.790521] rcu_scheduler_active = 1, debug_locks = 1
[  103.790524] 4 locks held by bash/4422:
[  103.790526]  #0:  (&buffer->mutex){+.+.+.}, at: [<ffffffff8114befa>] sysfs_write_file+0x3c/0x144
[  103.790537]  #1:  (s_active#102){.+.+.+}, at: [<ffffffff8114bfa5>] sysfs_write_file+0xe7/0x144
[  103.790544]  #2:  (&q->sysfs_lock){+.+.+.}, at: [<ffffffff812263b1>] queue_attr_store+0x49/0x8f
[  103.790552]  #3:  (&(&blkcg->lock)->rlock){......}, at: [<ffffffff8122e4db>] blkiocg_add_blkio_group+0x2b/0xad
[  103.790560]
[  103.790561] stack backtrace:
[  103.790564] Pid: 4422, comm: bash Not tainted 2.6.34-rc4-blkio-second-crash #81
[  103.790567] Call Trace:
[  103.790572]  [<ffffffff81068f57>] lockdep_rcu_dereference+0x9d/0xa5
[  103.790577]  [<ffffffff8107fac1>] css_id+0x44/0x57
[  103.790581]  [<ffffffff8122e503>] blkiocg_add_blkio_group+0x53/0xad
[  103.790586]  [<ffffffff81231936>] cfq_init_queue+0x139/0x32c
[  103.790591]  [<ffffffff8121f2d0>] elv_iosched_store+0xbf/0x1bf
[  103.790595]  [<ffffffff812263d8>] queue_attr_store+0x70/0x8f
[  103.790599]  [<ffffffff8114bfa5>] ? sysfs_write_file+0xe7/0x144
[  103.790603]  [<ffffffff8114bfc6>] sysfs_write_file+0x108/0x144
[  103.790609]  [<ffffffff810f527f>] vfs_write+0xae/0x10b
[  103.790612]  [<ffffffff81069863>] ? trace_hardirqs_on_caller+0x10c/0x130
[  103.790616]  [<ffffffff810f539c>] sys_write+0x4a/0x6e
[  103.790622]  [<ffffffff81002b5b>] system_call_fastpath+0x16/0x1b
[  103.790625]

Located-by: Miles Lane <miles.lane@gmail.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-06 08:54:00 +02:00
Dmitry Monakhov
50eaeb323a cfq-iosched: fix broken cfq_ref_get_cfqf() for CONFIG_BLK_CGROUP=y && CFQ_GROUP_IOSCHED=n
We should return the cfq_group for this case, not NULL.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-28 19:51:38 +02:00
Vivek Goyal
afc24d49c1 blk-cgroup: config options re-arrangement
This patch fixes few usability and configurability issues.

o All the cgroup based controller options are configurable from
  "Genral Setup/Control Group Support/" menu. blkio is the only exception.
  Hence make this option visible in above menu and make it configurable from
  there to bring it inline with rest of the cgroup based controllers.

o Get rid of CONFIG_DEBUG_CFQ_IOSCHED.

  This option currently does two things.

  - Enable printing of cgroup paths in blktrace
  - Enables CONFIG_DEBUG_BLK_CGROUP, which in turn displays additional stat
    files in cgroup.

  If we are using group scheduling, blktrace data is of not really much use
  if cgroup information is not present. To get this data, currently one has to
  also enable CONFIG_DEBUG_CFQ_IOSCHED, which in turn brings the overhead of
  all the additional debug stat files which is not desired.

  Hence, this patch moves printing of cgroup paths under
  CONFIG_CFQ_GROUP_IOSCHED.

  This allows us to get rid of CONFIG_DEBUG_CFQ_IOSCHED completely. Now all
  the debug stat files are controlled only by CONFIG_DEBUG_BLK_CGROUP which
  can be enabled through config menu.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Divyesh Shah <dpshah@google.com>
Reviewed-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-26 19:27:56 +02:00
Vivek Goyal
e5ff082e8a blkio: Fix another BUG_ON() crash due to cfqq movement across groups
o Once in a while, I was hitting a BUG_ON() in blkio code. empty_time was
  assuming that upon slice expiry, group can't be marked empty already (except
  forced dispatch).

  But this assumption is broken if cfqq can move (group_isolation=0) across
  groups after receiving a request.

  I think most likely in this case we got a request in a cfqq and accounted
  the rq in one group, later while adding the cfqq to tree, we moved the queue
  to a different group which was already marked empty and after dispatch from
  slice we found group already marked empty and raised alarm.

  This patch does not error out if group is already marked empty. This can
  introduce some empty_time stat error only in case of group_isolation=0. This
  is better than crashing. In case of group_isolation=1 we should still get
  same stats as before this patch.

[  222.308546] ------------[ cut here ]------------
[  222.309311] kernel BUG at block/blk-cgroup.c:236!
[  222.309311] invalid opcode: 0000 [#1] SMP
[  222.309311] last sysfs file: /sys/devices/virtual/block/dm-3/queue/scheduler
[  222.309311] CPU 1
[  222.309311] Modules linked in: dm_round_robin dm_multipath qla2xxx scsi_transport_fc dm_zero dm_mirror dm_region_hash dm_log dm_mod [last unloaded: scsi_wait_scan]
[  222.309311]
[  222.309311] Pid: 4780, comm: fio Not tainted 2.6.34-rc4-blkio-config #68 0A98h/HP xw8600 Workstation
[  222.309311] RIP: 0010:[<ffffffff8121ad88>]  [<ffffffff8121ad88>] blkiocg_set_start_empty_time+0x50/0x83
[  222.309311] RSP: 0018:ffff8800ba6e79f8  EFLAGS: 00010002
[  222.309311] RAX: 0000000000000082 RBX: ffff8800a13b7990 RCX: ffff8800a13b7808
[  222.309311] RDX: 0000000000002121 RSI: 0000000000000082 RDI: ffff8800a13b7a30
[  222.309311] RBP: ffff8800ba6e7a18 R08: 0000000000000000 R09: 0000000000000001
[  222.309311] R10: 000000000002f8c8 R11: ffff8800ba6e7ad8 R12: ffff8800a13b78ff
[  222.309311] R13: ffff8800a13b7990 R14: 0000000000000001 R15: ffff8800a13b7808
[  222.309311] FS:  00007f3beec476f0(0000) GS:ffff880001e40000(0000) knlGS:0000000000000000
[  222.309311] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  222.309311] CR2: 000000000040e7f0 CR3: 00000000a12d5000 CR4: 00000000000006e0
[  222.309311] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  222.309311] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[  222.309311] Process fio (pid: 4780, threadinfo ffff8800ba6e6000, task ffff8800b3d6bf00)
[  222.309311] Stack:
[  222.309311]  0000000000000001 ffff8800bab17a48 ffff8800bab17a48 ffff8800a13b7800
[  222.309311] <0> ffff8800ba6e7a68 ffffffff8121da35 ffff880000000001 00ff8800ba5c5698
[  222.309311] <0> ffff8800ba6e7a68 ffff8800a13b7800 0000000000000000 ffff8800bab17a48
[  222.309311] Call Trace:
[  222.309311]  [<ffffffff8121da35>] __cfq_slice_expired+0x2af/0x3ec
[  222.309311]  [<ffffffff8121fd7b>] cfq_dispatch_requests+0x2c8/0x8e8
[  222.309311]  [<ffffffff8120f1cd>] ? spin_unlock_irqrestore+0xe/0x10
[  222.309311]  [<ffffffff8120fb1a>] ? blk_insert_cloned_request+0x70/0x7b
[  222.309311]  [<ffffffff81210461>] blk_peek_request+0x191/0x1a7
[  222.309311]  [<ffffffffa0002799>] dm_request_fn+0x38/0x14c [dm_mod]
[  222.309311]  [<ffffffff810ae61f>] ? sync_page_killable+0x0/0x35
[  222.309311]  [<ffffffff81210fd4>] __generic_unplug_device+0x32/0x37
[  222.309311]  [<ffffffff81211274>] generic_unplug_device+0x2e/0x3c
[  222.309311]  [<ffffffffa00011a6>] dm_unplug_all+0x42/0x5b [dm_mod]
[  222.309311]  [<ffffffff8120ca37>] blk_unplug+0x29/0x2d
[  222.309311]  [<ffffffff8120ca4d>] blk_backing_dev_unplug+0x12/0x14
[  222.309311]  [<ffffffff81109a7a>] block_sync_page+0x35/0x39
[  222.309311]  [<ffffffff810ae616>] sync_page+0x41/0x4a
[  222.309311]  [<ffffffff810ae62d>] sync_page_killable+0xe/0x35
[  222.309311]  [<ffffffff8158aa59>] __wait_on_bit_lock+0x46/0x8f
[  222.309311]  [<ffffffff810ae4f5>] __lock_page_killable+0x66/0x6d
[  222.309311]  [<ffffffff81056f9c>] ? wake_bit_function+0x0/0x33
[  222.309311]  [<ffffffff810ae528>] lock_page_killable+0x2c/0x2e
[  222.309311]  [<ffffffff810afbc5>] generic_file_aio_read+0x361/0x4f0
[  222.309311]  [<ffffffff810ea044>] do_sync_read+0xcb/0x108
[  222.309311]  [<ffffffff811e42f7>] ? security_file_permission+0x16/0x18
[  222.309311]  [<ffffffff810ea6ab>] vfs_read+0xab/0x108
[  222.309311]  [<ffffffff810ea7c8>] sys_read+0x4a/0x6e
[  222.309311]  [<ffffffff81002b5b>] system_call_fastpath+0x16/0x1b
[  222.309311] Code: 58 01 00 00 00 48 89 c6 75 0a 48 83 bb 60 01 00 00 00 74 09 48 8d bb a0 00 00 00 eb 35 41 fe cc 74 0d f6 83 c0 01 00 00 04 74 04 <0f> 0b eb fe 48 89 75 e8 e8 be e0 de ff 66 83 8b c0 01 00 00 04
[  222.309311] RIP  [<ffffffff8121ad88>] blkiocg_set_start_empty_time+0x50/0x83
[  222.309311]  RSP <ffff8800ba6e79f8>
[  222.309311] ---[ end trace 32b4f71dffc15712 ]---

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Divyesh Shah <dpshah@google.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-26 19:25:11 +02:00
Vivek Goyal
7f1dc8a2d2 blkio: Fix blkio crash during rq stat update
blkio + cfq was crashing even when two sequential readers were put in two
separate cgroups (group_isolation=0).

The reason being that cfqq can migrate across groups based on its being
sync-noidle or not, it can happen that at request insertion time, cfqq
belonged to one cfqg and at request dispatch time, it belonged to root
group. In this case request stats per cgroup can go wrong and it also runs
into BUG_ON().

This patch implements rq stashing away a cfq group pointer and not relying
on cfqq->cfqg pointer alone for rq stat accounting.

[   65.163523] ------------[ cut here ]------------
[   65.164301] kernel BUG at block/blk-cgroup.c:117!
[   65.164301] invalid opcode: 0000 [#1] SMP
[   65.164301] last sysfs file: /sys/devices/pci0000:00/0000:00:05.0/0000:60:00.1/host9/rport-9:0-0/target9:0:0/9:0:0:2/block/sde/stat
[   65.164301] CPU 1
[   65.164301] Modules linked in: dm_round_robin dm_multipath qla2xxx scsi_transport_fc dm_zero dm_mirror dm_region_hash dm_log dm_mod [last unloaded: scsi_wait_scan]
[   65.164301]
[   65.164301] Pid: 4505, comm: fio Not tainted 2.6.34-rc4-blk-for-35 #34 0A98h/HP xw8600 Workstation
[   65.164301] RIP: 0010:[<ffffffff8121924f>]  [<ffffffff8121924f>] blkiocg_update_io_remove_stats+0x5b/0xaf
[   65.164301] RSP: 0018:ffff8800ba5a79e8  EFLAGS: 00010046
[   65.164301] RAX: 0000000000000096 RBX: ffff8800bb268d60 RCX: 0000000000000000
[   65.164301] RDX: ffff8800bb268eb8 RSI: 0000000000000000 RDI: ffff8800bb268e00
[   65.164301] RBP: ffff8800ba5a7a08 R08: 0000000000000064 R09: 0000000000000001
[   65.164301] R10: 0000000000079640 R11: ffff8800a0bd5bf0 R12: ffff8800bab4af01
[   65.164301] R13: ffff8800bab4af00 R14: ffff8800bb1d8928 R15: 0000000000000000
[   65.164301] FS:  00007f18f75056f0(0000) GS:ffff880001e40000(0000) knlGS:0000000000000000
[   65.164301] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   65.164301] CR2: 000000000040e7f0 CR3: 00000000ba52b000 CR4: 00000000000006e0
[   65.164301] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   65.164301] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[   65.164301] Process fio (pid: 4505, threadinfo ffff8800ba5a6000, task ffff8800ba45ae80)
[   65.164301] Stack:
[   65.164301]  ffff8800ba5a7a08 ffff8800ba722540 ffff8800bab4af68 ffff8800bab4af68
[   65.164301] <0> ffff8800ba5a7a38 ffffffff8121d814 ffff8800ba722540 ffff8800bab4af68
[   65.164301] <0> ffff8800ba722540 ffff8800a08f6800 ffff8800ba5a7a68 ffffffff8121d8ca
[   65.164301] Call Trace:
[   65.164301]  [<ffffffff8121d814>] cfq_remove_request+0xe4/0x116
[   65.164301]  [<ffffffff8121d8ca>] cfq_dispatch_insert+0x84/0xe1
[   65.164301]  [<ffffffff8121e833>] cfq_dispatch_requests+0x767/0x8e8
[   65.164301]  [<ffffffff8120e524>] ? submit_bio+0xc3/0xcc
[   65.164301]  [<ffffffff810ad657>] ? sync_page_killable+0x0/0x35
[   65.164301]  [<ffffffff8120ea8d>] blk_peek_request+0x191/0x1a7
[   65.164301]  [<ffffffffa000109c>] ? dm_get_live_table+0x44/0x4f [dm_mod]
[   65.164301]  [<ffffffffa0002799>] dm_request_fn+0x38/0x14c [dm_mod]
[   65.164301]  [<ffffffff810ad657>] ? sync_page_killable+0x0/0x35
[   65.164301]  [<ffffffff8120f600>] __generic_unplug_device+0x32/0x37
[   65.164301]  [<ffffffff8120f8a0>] generic_unplug_device+0x2e/0x3c
[   65.164301]  [<ffffffffa00011a6>] dm_unplug_all+0x42/0x5b [dm_mod]
[   65.164301]  [<ffffffff8120b063>] blk_unplug+0x29/0x2d
[   65.164301]  [<ffffffff8120b079>] blk_backing_dev_unplug+0x12/0x14
[   65.164301]  [<ffffffff81108a82>] block_sync_page+0x35/0x39
[   65.164301]  [<ffffffff810ad64e>] sync_page+0x41/0x4a
[   65.164301]  [<ffffffff810ad665>] sync_page_killable+0xe/0x35
[   65.164301]  [<ffffffff81589027>] __wait_on_bit_lock+0x46/0x8f
[   65.164301]  [<ffffffff810ad52d>] __lock_page_killable+0x66/0x6d
[   65.164301]  [<ffffffff81055fd4>] ? wake_bit_function+0x0/0x33
[   65.164301]  [<ffffffff810ad560>] lock_page_killable+0x2c/0x2e
[   65.164301]  [<ffffffff810aebfd>] generic_file_aio_read+0x361/0x4f0
[   65.164301]  [<ffffffff810e906c>] do_sync_read+0xcb/0x108
[   65.164301]  [<ffffffff811e32a3>] ? security_file_permission+0x16/0x18
[   65.164301]  [<ffffffff810e96d3>] vfs_read+0xab/0x108
[   65.164301]  [<ffffffff810e97f0>] sys_read+0x4a/0x6e
[   65.164301]  [<ffffffff81002b5b>] system_call_fastpath+0x16/0x1b
[   65.164301] Code: 00 74 1c 48 8b 8b 60 01 00 00 48 85 c9 75 04 0f 0b eb fe 48 ff c9 48 89 8b 60 01 00 00 eb 1a 48 8b 8b 58 01 00 00 48 85 c9 75 04 <0f> 0b eb fe 48 ff c9 48 89 8b 58 01 00 00 45 84 e4 74 16 48 8b
[   65.164301] RIP  [<ffffffff8121924f>] blkiocg_update_io_remove_stats+0x5b/0xaf
[   65.164301]  RSP <ffff8800ba5a79e8>
[   65.164301] ---[ end trace 1b2b828753032e68 ]---

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-21 17:44:16 +02:00
Divyesh Shah
8d2a91f896 blkio: Initialize blkg->stats_lock for the root cfqg too
This fixes the lockdep warning reported by Gui Jianfeng.

Signed-off-by: Divyesh Shah <dpshah@google.com>
Reviewed-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-16 08:10:51 +02:00
Divyesh Shah
28baf44299 blkio: Fix compile errors
Fixes compile errors in blk-cgroup code for empty_time stat and a merge fix in
CFQ. The first error was when CONFIG_DEBUG_CFQ_IOSCHED is not set.

Signed-off-by: Divyesh Shah <dpshah@google.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-14 11:22:38 +02:00
Jens Axboe
4facdaec1c Merge branch 'master' into for-2.6.35
Conflicts:
	block/blk-cgroup.c
	block/cfq-iosched.c

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-13 20:03:21 +02:00
Divyesh Shah
a11cdaa7af block: Update to io-controller stats
Changelog from v1:
o Call blkiocg_update_idle_time_stats() at cfq_rq_enqueued() instead of at
  dispatch time.

Changelog from original patchset: (in response to Vivek Goyal's comments)
o group blkiocg_update_blkio_group_dequeue_stats() with other DEBUG functions
o rename blkiocg_update_set_active_queue_stats() to
  blkiocg_update_avg_queue_size_stats()
o s/request/io/ in blkiocg_update_request_add_stats() and
  blkiocg_update_request_remove_stats()
o Call cfq_del_timer() at request dispatch() instead of
  blkiocg_update_idle_time_stats()

Signed-off-by: Divyesh Shah<dpshah@google.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-13 19:59:17 +02:00
Gui Jianfeng
34d0f179d6 io-controller: Add a new interface "weight_device" for IO-Controller
Currently, IO Controller makes use of blkio.weight to assign weight for
all devices. Here a new user interface "blkio.weight_device" is introduced to
assign different weights for different devices. blkio.weight becomes the
default value for devices which are not configured by "blkio.weight_device"

You can use the following format to assigned specific weight for a given
device:
#echo "major:minor weight" > blkio.weight_device

major:minor represents device number.

And you can remove weight for a given device as following:
#echo "major:minor 0" > blkio.weight_device

V1->V2 changes:
- use user interface "weight_device" instead of "policy" suggested by Vivek
- rename some struct suggested by Vivek
- rebase to 2.6-block "for-linus" branch
- remove an useless list_empty check pointed out by Li Zefan
- some trivial typo fix

V2->V3 changes:
- Move policy_*_node() functions up to get rid of forward declarations
- rename related functions by adding prefix "blkio_"

Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-13 10:14:20 +02:00
Linus Torvalds
2f4084209a Merge branch 'for-linus' of git://git.kernel.dk/linux-2.6-block
* 'for-linus' of git://git.kernel.dk/linux-2.6-block: (34 commits)
  cfq-iosched: Fix the incorrect timeslice accounting with forced_dispatch
  loop: Update mtime when writing using aops
  block: expose the statistics in blkio.time and blkio.sectors for the root cgroup
  backing-dev: Handle class_create() failure
  Block: Fix block/elevator.c elevator_get() off-by-one error
  drbd: lc_element_by_index() never returns NULL
  cciss: unlock on error path
  cfq-iosched: Do not merge queues of BE and IDLE classes
  cfq-iosched: Add additional blktrace log messages in CFQ for easier debugging
  i2o: Remove the dangerous kobj_to_i2o_device macro
  block: remove 16 bytes of padding from struct request on 64bits
  cfq-iosched: fix a kbuild regression
  block: make CONFIG_BLK_CGROUP visible
  Remove GENHD_FL_DRIVERFS
  block: Export max number of segments and max segment size in sysfs
  block: Finalize conversion of block limits functions
  block: Fix overrun in lcm() and move it to lib
  vfs: improve writeback_inodes_wb()
  paride: fix off-by-one test
  drbd: fix al-to-on-disk-bitmap for 4k logical_block_size
  ...
2010-04-09 11:50:29 -07:00
Divyesh Shah
3440c49f5c cfq-iosched: Fix the incorrect timeslice accounting with forced_dispatch
When CFQ dispatches requests forcefully due to a barrier or changing iosched,
it runs through all cfqq's dispatching requests and then expires each queue.
However, it does not activate a cfqq before flushing its IOs resulting in
using stale values for computing slice_used.
This patch fixes it by calling activate queue before flushing reuqests from
each queue.

This is useful mostly for barrier requests because when the iosched is changing
it really doesnt matter if we have incorrect accounting since we're going to
break down all structures anyway.

We also now expire the current timeslice before moving on with the dispatch
to accurately account slice used for that cfqq.

Signed-off-by: Divyesh Shah<dpshah@google.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-09 09:29:57 +02:00
Divyesh Shah
812df48d12 blkio: Add more debug-only per-cgroup stats
1) group_wait_time - This is the amount of time the cgroup had to wait to get a
  timeslice for one of its queues from when it became busy, i.e., went from 0
  to 1 request queued. This is different from the io_wait_time which is the
  cumulative total of the amount of time spent by each IO in that cgroup waiting
  in the scheduler queue. This stat is a great way to find out any jobs in the
  fleet that are being starved or waiting for longer than what is expected (due
  to an IO controller bug or any other issue).
2) empty_time - This is the amount of time a cgroup spends w/o any pending
   requests. This stat is useful when a job does not seem to be able to use its
   assigned disk share by helping check if that is happening due to an IO
   controller bug or because the job is not submitting enough IOs.
3) idle_time - This is the amount of time spent by the IO scheduler idling
   for a given cgroup in anticipation of a better request than the exising ones
   from other queues/cgroups.

All these stats are recorded using start and stop events. When reading these
stats, we do not add the delta between the current time and the last start time
if we're between the start and stop events. We avoid doing this to make sure
that these numbers are always monotonically increasing when read. Since we're
using sched_clock() which may use the tsc as its source, it may induce some
inconsistency (due to tsc resync across cpus) if we included the current delta.

Signed-off-by: Divyesh Shah<dpshah@google.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-09 08:36:08 +02:00
Divyesh Shah
cdc1184cf4 blkio: Add io_queued and avg_queue_size stats
These stats are useful for getting a feel for the queue depth of the cgroup,
i.e., how filled up its queues are at a given instant and over the existence of
the cgroup. This ability is useful when debugging problems in the wild as it
helps understand the application's IO pattern w/o having to read through the
userspace code (coz its tedious or just not available) or w/o the ability
to run blktrace (since you may not have root access and/or not want to disturb
performance).

Signed-off-by: Divyesh Shah<dpshah@google.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-09 08:36:08 +02:00
Divyesh Shah
812d402648 blkio: Add io_merged stat
This includes both the number of bios merged into requests belonging to this
cgroup as well as the number of requests merged together.
In the past, we've observed different merging behavior across upstream kernels,
some by design some actual bugs. This stat helps a lot in debugging such
problems when applications report decreased throughput with a new kernel
version.

This needed adding an extra elevator function to capture bios being merged as I
did not want to pollute elevator code with blkiocg knowledge and hence needed
the accounting invocation to come from CFQ.

Signed-off-by: Divyesh Shah<dpshah@google.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-09 08:36:07 +02:00
Divyesh Shah
84c124da9f blkio: Changes to IO controller additional stats patches
that include some minor fixes and addresses all comments.

Changelog: (most based on Vivek Goyal's comments)
o renamed blkiocg_reset_write to blkiocg_reset_stats
o more clarification in the documentation on io_service_time and io_wait_time
o Initialize blkg->stats_lock
o rename io_add_stat to blkio_add_stat and declare it static
o use bool for direction and sync
o derive direction and sync info from existing rq methods
o use 12 for major:minor string length
o define io_service_time better to cover the NCQ case
o add a separate reset_stats interface
o make the indexed stats a 2d array to simplify macro and function pointer code
o blkio.time now exports in jiffies as before
o Added stats description in patch description and
  Documentation/cgroup/blkio-controller.txt
o Prefix all stats functions with blkio and make them static as applicable
o replace IO_TYPE_MAX with IO_TYPE_TOTAL
o Moved #define constant to top of blk-cgroup.c
o Pass dev_t around instead of char *
o Add note to documentation file about resetting stats
o use BLK_CGROUP_MODULE in addition to BLK_CGROUP config option in #ifdef
  statements
o Avoid struct request specific knowledge in blk-cgroup. blk-cgroup.h now has
  rq_direction() and rq_sync() functions which are used by CFQ and when using
  io-controller at a higher level, bio_* functions can be added.

Signed-off-by: Divyesh Shah<dpshah@google.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-09 08:31:19 +02:00
Ricky Benitez
a74b2adae0 block: expose the statistics in blkio.time and blkio.sectors for the root cgroup
Currently, the io statistics for the root cgroup are maintained, but
they are not shown because the device information is not available at
the point that the root blkio cgroup is created. This patch updates
the device information when the statistics are updated so that the
statistics become visible.

Signed-off-by: Ricky Benitez <rickyb@google.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-05 18:22:17 +02:00
Divyesh Shah
9195291e5f blkio: Increment the blkio cgroup stats for real now
We also add start_time_ns and io_start_time_ns fields to struct request
here to record the time when a request is created and when it is
dispatched to device. We use ns uints here as ms and jiffies are
not very useful for non-rotational media.

Signed-off-by: Divyesh Shah<dpshah@google.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-02 08:44:37 +02:00
Divyesh Shah
303a3acb23 blkio: Add io controller stats like
- io_service_time
- io_wait_time
- io_serviced
- io_service_bytes

These stats are accumulated per operation type helping us to distinguish between
read and write, and sync and async IO. This patch does not increment any of
these stats.

Signed-off-by: Divyesh Shah<dpshah@google.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-02 08:44:36 +02:00
Divyesh Shah
9a0785b0da blkio: Remove per-cfqq nr_sectors as we'll be passing
that info at request dispatch with other stats now. This patch removes the
existing support for accounting sectors for a blkio_group. This will be added
back differently in the next two patches.

Signed-off-by: Divyesh Shah<dpshah@google.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-04-02 08:44:36 +02:00
Tejun Heo
5a0e3ad6af include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h
percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files.  percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.

percpu.h -> slab.h dependency is about to be removed.  Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability.  As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.

  http://userweb.kernel.org/~tj/misc/slabh-sweep.py

The script does the followings.

* Scan files for gfp and slab usages and update includes such that
  only the necessary includes are there.  ie. if only gfp is used,
  gfp.h, if slab is used, slab.h.

* When the script inserts a new include, it looks at the include
  blocks and try to put the new include such that its order conforms
  to its surrounding.  It's put in the include block which contains
  core kernel includes, in the same order that the rest are ordered -
  alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
  doesn't seem to be any matching order.

* If the script can't find a place to put a new include (mostly
  because the file doesn't have fitting include block), it prints out
  an error message indicating which .h file needs to be added to the
  file.

The conversion was done in the following steps.

1. The initial automatic conversion of all .c files updated slightly
   over 4000 files, deleting around 700 includes and adding ~480 gfp.h
   and ~3000 slab.h inclusions.  The script emitted errors for ~400
   files.

2. Each error was manually checked.  Some didn't need the inclusion,
   some needed manual addition while adding it to implementation .h or
   embedding .c file was more appropriate for others.  This step added
   inclusions to around 150 files.

3. The script was run again and the output was compared to the edits
   from #2 to make sure no file was left behind.

4. Several build tests were done and a couple of problems were fixed.
   e.g. lib/decompress_*.c used malloc/free() wrappers around slab
   APIs requiring slab.h to be added manually.

5. The script was run on all .h files but without automatically
   editing them as sprinkling gfp.h and slab.h inclusions around .h
   files could easily lead to inclusion dependency hell.  Most gfp.h
   inclusion directives were ignored as stuff from gfp.h was usually
   wildly available and often used in preprocessor macros.  Each
   slab.h inclusion directive was examined and added manually as
   necessary.

6. percpu.h was updated not to include slab.h.

7. Build test were done on the following configurations and failures
   were fixed.  CONFIG_GCOV_KERNEL was turned off for all tests (as my
   distributed build env didn't work with gcov compiles) and a few
   more options had to be turned off depending on archs to make things
   build (like ipr on powerpc/64 which failed due to missing writeq).

   * x86 and x86_64 UP and SMP allmodconfig and a custom test config.
   * powerpc and powerpc64 SMP allmodconfig
   * sparc and sparc64 SMP allmodconfig
   * ia64 SMP allmodconfig
   * s390 SMP allmodconfig
   * alpha SMP allmodconfig
   * um on x86_64 SMP allmodconfig

8. percpu.h modifications were reverted so that it could be applied as
   a separate patch and serve as bisection point.

Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.

Signed-off-by: Tejun Heo <tj@kernel.org>
Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
2010-03-30 22:02:32 +09:00
Divyesh Shah
39c01b219f cfq-iosched: Do not merge queues of BE and IDLE classes
Even if they are found to be co-operating.

The prio_trees do not have any IDLE cfqqs on them. cfq_close_cooperator()
is called from cfq_select_queue() and cfq_completed_request(). The latter
ensures that the close cooperator code does not get invoked if the current
cfqq is of class IDLE but the former doesn't seem to have any such checks.
So an IDLE cfqq may get merged with a BE cfqq from the same group which
should be avoided.

Signed-off-by: Divyesh Shah<dpshah@google.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-03-25 15:46:38 +01:00
Divyesh Shah
b1ffe737f5 cfq-iosched: Add additional blktrace log messages in CFQ for easier debugging
These have helped us debug some issues we've noticed in earlier IO
controller versions and should be useful now as well. The extra logging
covers:
- idling behavior. Since there are so many conditions based on which we decide
to idle or not, this patch adds a log message for some conditions that we've
found useful.
- workload slices and current prio and workload type

Changelog from v1:
o moved log message from cfq_set_active_queue() to __cfq_set_active_queue()
o changed queue_count to st->count

Signed-off-by: Divyesh Shah<dpshah@google.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-03-25 15:45:03 +01:00
Shaohua Li
e9ce335df5 cfq-iosched: fix a kbuild regression
Alex Shi reported a kbuild regression which is about 10% performance lost.
He bisected to this commit: 3dde36ddea.
The reason is cfqq_close() can't find close cooperator. Restoring
cfq_rq_close()'s threshold to original value makes the regression go away.

Since for_preempt parameter isn't used anymore, this patch deletes it.

Reported-by: Alex Shi <alex.shi@intel.com>
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Acked-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-03-19 08:03:04 +01:00
Richard Kennedy
73e9ffdd0c cfq: remove 8 bytes of padding from cfq_rb_root on 64 bit builds
Reorder cfq_rb_root to remove 8 bytes of padding on 64 bit builds.

Consequently removing 56 bytes from cfq_group and 64 bytes from
cfq_data.

Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-03-01 10:50:20 +01:00
Shaohua Li
abc3c744d0 cfq-iosched: quantum check tweak
Currently a queue can only dispatch up to 4 requests if there are other queues.
This isn't optimal, device can handle more requests, for example, AHCI can
handle 31 requests. I can understand the limit is for fairness, but we could
do a tweak: if the queue still has a lot of slice left, sounds we could
ignore the limit. Test shows this boost my workload (two thread randread of
a SSD) from 78m/s to 100m/s.
Thanks for suggestions from Corrado and Vivek for the patch.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-03-01 09:20:54 +01:00
Corrado Zoccolo
53c583d226 cfq-iosched: requests "in flight" vs "in driver" clarification
Counters for requests "in flight" and "in driver" are used asymmetrically
in cfq_may_dispatch, and have slightly different meaning.
We split the rq_in_flight counter (was sync_flight) to count both sync
and async requests, in order to use this one, which is more accurate in
some corner cases.
The rq_in_driver counter is coalesced, since individual sync/async counts
are not used any more.

Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-02-28 19:45:05 +01:00
Corrado Zoccolo
41647e7a91 cfq-iosched: rethink seeky detection for SSDs
CFQ currently applies the same logic of detecting seeky queues and
grouping them together for rotational disks as well as SSDs.
For SSDs, the time to complete a request doesn't depend on the
request location, but only on the size.
This patch therefore changes the criterion to group queues by
request size in case of SSDs, in order to achieve better fairness.

Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-02-28 19:41:25 +01:00
Corrado Zoccolo
3dde36ddea cfq-iosched: rework seeky detection
Current seeky detection is based on average seek lenght.
This is suboptimal, since the average will not distinguish between:
* a process doing medium sized seeks
* a process doing some sequential requests interleaved with larger seeks
and even a medium seek can take lot of time, if the requested sector
happens to be behind the disk head in the rotation (50% probability).

Therefore, we change the seeky queue detection to work as follows:
* each request can be classified as sequential if it is very close to
  the current head position, i.e. it is likely in the disk cache (disks
  usually read more data than requested, and put it in cache for
  subsequent reads). Otherwise, the request is classified as seeky.
* an history window of the last 32 requests is kept, storing the
  classification result.
* A queue is marked as seeky if more than 1/8 of the last 32 requests
  were seeky.

This patch fixes a regression reported by Yanmin, on mmap 64k random
reads.

Reported-by: Yanmin Zhang <yanmin_zhang@linux.intel.com>
Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-02-28 19:41:25 +01:00
Gui Jianfeng
024f906616 cfq: Remove useless css reference get
There's no need to take css reference here, for the caller
has already called rcu_read_lock() to prevent cgroup from
being removed.

Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-02-26 08:56:15 +01:00
Richard Kennedy
c4081ba5c9 cfq: reorder cfq_queue removing padding on 64bit
This removes 8 bytes of padding from struct cfq_queue on 64 bit builds,
shrinking it's size to 256 bytes, so fitting into 1 fewer cachelines and
allowing 1 more object/slab in it's kmem_cache.

Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
----
patch against 2.6.33-rc8
tested on x86_64 AMDX2
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-02-22 13:49:24 +01:00
Shaohua Li
ae54abed63 cfq-iosched: split seeky coop queues after one slice
Currently we split seeky coop queues after 1s, which is too big. Below patch
marks seeky coop queue split_coop flag after one slice. After that, if new
requests come in, the queues will be splitted. Patch is suggested by Corrado.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Reviewed-by: Corrado Zoccolo <czoccolo@gmail.com>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-02-05 13:11:45 +01:00
Vivek Goyal
1efe8fe1c2 cfq-iosched: Do not idle on async queues
Few weeks back, Shaohua Li had posted similar patch. I am reposting it
with more test results.

This patch does two things.

- Do not idle on async queues.

- It also changes the write queue depth CFQ drives (cfq_may_dispatch()).
  Currently, we seem to driving queue depth of 1 always for WRITES. This is
  true even if there is only one write queue in the system and all the logic
  of infinite queue depth in case of single busy queue as well as slowly
  increasing queue depth based on last delayed sync request does not seem to
  be kicking in at all.

This patch will allow deeper WRITE queue depths (subjected to the other
WRITE queue depth contstraints like cfq_quantum and last delayed sync
request).

Shaohua Li had reported getting more out of his SSD. For me, I have got
one Lun exported from an HP EVA and when pure buffered writes are on, I
can get more out of the system. Following are test results of pure
buffered writes (with end_fsync=1) with vanilla and patched kernel. These
results are average of 3 sets of run with increasing number of threads.

AVERAGE[bufwfs][vanilla]
-------
job       Set NR  ReadBW(KB/s)   MaxClat(us)    WriteBW(KB/s)  MaxClat(us)
---       --- --  ------------   -----------    -------------  -----------
bufwfs    3   1   0              0              95349          474141
bufwfs    3   2   0              0              100282         806926
bufwfs    3   4   0              0              109989         2.7301e+06
bufwfs    3   8   0              0              116642         3762231
bufwfs    3   16  0              0              118230         6902970

AVERAGE[bufwfs] [patched kernel]
-------
bufwfs    3   1   0              0              270722         404352
bufwfs    3   2   0              0              206770         1.06552e+06
bufwfs    3   4   0              0              195277         1.62283e+06
bufwfs    3   8   0              0              260960         2.62979e+06
bufwfs    3   16  0              0              299260         1.70731e+06

I also ran buffered writes along with some sequential reads and some
buffered reads going on in the system on a SATA disk because the potential
risk could be that we should not be driving queue depth higher in presence
of sync IO going to keep the max clat low.

With some random and sequential reads going on in the system on one SATA
disk I did not see any significant increase in max clat. So it looks like
other WRITE queue depth control logic is doing its job. Here are the
results.

AVERAGE[brr, bsr, bufw together] [vanilla]
-------
job       Set NR  ReadBW(KB/s)   MaxClat(us)    WriteBW(KB/s)  MaxClat(us)
---       --- --  ------------   -----------    -------------  -----------
brr       3   1   850            546345         0              0
bsr       3   1   14650          729543         0              0
bufw      3   1   0              0              23908          8274517

brr       3   2   981.333        579395         0              0
bsr       3   2   14149.7        1175689        0              0
bufw      3   2   0              0              21921          1.28108e+07

brr       3   4   898.333        1.75527e+06    0              0
bsr       3   4   12230.7        1.40072e+06    0              0
bufw      3   4   0              0              19722.3        2.4901e+07

brr       3   8   900            3160594        0              0
bsr       3   8   9282.33        1.91314e+06    0              0
bufw      3   8   0              0              18789.3        23890622

AVERAGE[brr, bsr, bufw mixed] [patched kernel]
-------
job       Set NR  ReadBW(KB/s)   MaxClat(us)    WriteBW(KB/s)  MaxClat(us)
---       --- --  ------------   -----------    -------------  -----------
brr       3   1   837            417973         0              0
bsr       3   1   14357.7        591275         0              0
bufw      3   1   0              0              24869.7        8910662

brr       3   2   1038.33        543434         0              0
bsr       3   2   13351.3        1205858        0              0
bufw      3   2   0              0              18626.3        13280370

brr       3   4   913            1.86861e+06    0              0
bsr       3   4   12652.3        1430974        0              0
bufw      3   4   0              0              15343.3        2.81305e+07

brr       3   8   890            2.92695e+06    0              0
bsr       3   8   9635.33        1.90244e+06    0              0
bufw      3   8   0              0              17200.3        24424392

So looks like it might make sense to include this patch.

Thanks
Vivek

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-02-02 20:46:10 +01:00
Divyesh Shah
875feb63b9 cfq-iosched: Respect ioprio_class when preempting
In cfq_should_preempt(), we currently allow some cases where a non-RT request
can preempt an ongoing RT cfqq timeslice. This should not happen.
Examples include:

o A sync_noidle wl type non-RT request pre-empting a sync_noidle wl type cfqq
  on which we are idling.
o Once we have per-cgroup async queues, a non-RT sync request pre-empting a RT
  async cfqq.

Signed-off-by: Divyesh Shah<dpshah@google.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-01-11 16:16:18 +01:00
Shaohua Li
2f7a2d89a8 cfq-iosched: don't regard requests with long distance as close
seek_mean could be very big sometimes, using it as close criteria is meaningless
as this doen't improve any performance. So if it's big, let's fallback to
default value.

Reviewed-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Shaohua Li<shaohua.li@intel.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-28 13:18:44 +01:00
Vivek Goyal
65b32a573e cfq-iosched: Remove prio_change logic for workload selection
o CFQ now internally divides cfq queues in therr workload categories. sync-idle,
  sync-noidle and async. Which workload to run depends primarily on rb_key
  offset across three service trees. Which is a combination of mulitiple things
  including what time queue got queued on the service tree.

  There is one exception though. That is if we switched the prio class, say
  we served some RT tasks and again started serving BE class, then with-in
  BE class we always started with sync-noidle workload irrespective of rb_key
  offset in service trees.

  This can provide better latencies for sync-noidle workload in the presence
  of RT tasks.

o This patch gets rid of that exception and which workload to run with-in
  class always depends on lowest rb_key across service trees. The reason
  being that now we have multiple BE class groups and if we always switch
  to sync-noidle workload with-in group, we can potentially starve a sync-idle
  workload with-in group. Same is true for async workload which will be in
  root group. Also the workload-switching with-in group will become very
  unpredictable as it now depends whether some RT workload was running in
  the system or not.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Acked-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-18 12:40:21 +01:00
Vivek Goyal
fb104db41e cfq-iosched: Get rid of nr_groups
o Currently code does not seem to be using cfqd->nr_groups. Get rid of it.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-18 12:40:21 +01:00
Vivek Goyal
1db32c4060 cfq-iosched: Remove the check for same cfq group from allow_merge
o allow_merge() already checks if submitting task is pointing to same cfqq
  as rq has been queued in. If everything is fine, we should not be having
  a task in one cgroup and having a pointer to cfqq in other cgroup.

  Well I guess in some situations it can happen and that is, when a random
  IO queue has been moved into root cgroup for group_isolation=0. In
  this case, tasks's cgroup/group is different from where actually cfqq is,
  but this is intentional and in this case merging should be allowed.

  The second situation is where due to close cooperator patches, multiple
  processes can be sharing a cfqq. If everything implemented right, we should
  not end up in a situation where tasks from different processes in different
  groups are sharing the same cfqq as we allow merging of cooperating queues
  only if they are in same group.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-18 12:40:21 +01:00
Gui Jianfeng
66ae291978 cfq: set workload as expired if it doesn't have any slice left
When a group is resumed, if it doesn't have workload slice left,
we should set workload_expires as expired. Otherwise, we might
start from where we left in previous group by error.
Thanks the idea from Corrado.

Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-15 10:08:45 +01:00
Vivek Goyal
82bbbf28db Fix a CFQ crash in "for-2.6.33" branch of block tree
I think my previous patch introduced a bug which can lead to CFQ hitting
BUG_ON().

The offending commit in for-2.6.33 branch is.

commit 7667aa0630
Author: Vivek Goyal <vgoyal@redhat.com>
Date:   Tue Dec 8 17:52:58 2009 -0500

    cfq-iosched: Take care of corner cases of group losing share due to deletion

While doing some stress testing on my box, I enountered following.

login: [ 3165.148841] BUG: scheduling while
atomic: swapper/0/0x10000100
[ 3165.149821] Modules linked in: cfq_iosched dm_multipath qla2xxx igb
scsi_transport_fc dm_snapshot [last unloaded: scsi_wait_scan]
[ 3165.149821] Pid: 0, comm: swapper Not tainted
2.6.32-block-for-33-merged-new #3
[ 3165.149821] Call Trace:
[ 3165.149821]  <IRQ>  [<ffffffff8103fab8>] __schedule_bug+0x5c/0x60
[ 3165.149821]  [<ffffffff8103afd7>] ? __wake_up+0x44/0x4d
[ 3165.149821]  [<ffffffff8153a979>] schedule+0xe3/0x7bc
[ 3165.149821]  [<ffffffff8103a796>] ? cpumask_next+0x1d/0x1f
[ 3165.149821]  [<ffffffffa000b21d>] ? cfq_dispatch_requests+0x6ba/0x93e
[cfq_iosched]
[ 3165.149821]  [<ffffffff810422d8>] __cond_resched+0x2a/0x35
[ 3165.149821]  [<ffffffffa000b21d>] ? cfq_dispatch_requests+0x6ba/0x93e
[cfq_iosched]
[ 3165.149821]  [<ffffffff8153b1ee>] _cond_resched+0x2c/0x37
[ 3165.149821]  [<ffffffff8100e2db>] is_valid_bugaddr+0x16/0x2f
[ 3165.149821]  [<ffffffff811e4161>] report_bug+0x18/0xac
[ 3165.149821]  [<ffffffff8100f1fc>] die+0x39/0x63
[ 3165.149821]  [<ffffffff8153cde1>] do_trap+0x11a/0x129
[ 3165.149821]  [<ffffffff8100d470>] do_invalid_op+0x96/0x9f
[ 3165.149821]  [<ffffffffa000b21d>] ? cfq_dispatch_requests+0x6ba/0x93e
[cfq_iosched]
[ 3165.149821]  [<ffffffff81034b4d>] ? enqueue_task+0x5c/0x67
[ 3165.149821]  [<ffffffff8103ae83>] ? task_rq_unlock+0x11/0x13
[ 3165.149821]  [<ffffffff81041aae>] ? try_to_wake_up+0x292/0x2a4
[ 3165.149821]  [<ffffffff8100c935>] invalid_op+0x15/0x20
[ 3165.149821]  [<ffffffffa000b21d>] ? cfq_dispatch_requests+0x6ba/0x93e
[cfq_iosched]
[ 3165.149821]  [<ffffffff810df5a6>] ? virt_to_head_page+0xe/0x2f
[ 3165.149821]  [<ffffffff811d8c2a>] blk_peek_request+0x191/0x1a7
[ 3165.149821]  [<ffffffff811e5b8d>] ? kobject_get+0x1a/0x21
[ 3165.149821]  [<ffffffff812c8d4c>] scsi_request_fn+0x82/0x3df
[ 3165.149821]  [<ffffffff8110b2de>] ? bio_fs_destructor+0x15/0x17
[ 3165.149821]  [<ffffffff810df5a6>] ? virt_to_head_page+0xe/0x2f
[ 3165.149821]  [<ffffffff811d931f>] __blk_run_queue+0x42/0x71
[ 3165.149821]  [<ffffffff811d9403>] blk_run_queue+0x26/0x3a
[ 3165.149821]  [<ffffffff812c8761>] scsi_run_queue+0x2de/0x375
[ 3165.149821]  [<ffffffff812b60ac>] ? put_device+0x17/0x19
[ 3165.149821]  [<ffffffff812c92d7>] scsi_next_command+0x3b/0x4b
[ 3165.149821]  [<ffffffff812c9b9f>] scsi_io_completion+0x1c9/0x3f5
[ 3165.149821]  [<ffffffff812c3c36>] scsi_finish_command+0xb5/0xbe

I think I have hit following BUG_ON() in cfq_dispatch_request().

BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));

Please find attached the patch to fix it. I have done some stress testing
with it and have not seen it happening again.

o We should wait on a queue even after slice expiry only if it is empty. If
  queue is not empty then continue to expire it.

o If we decide to keep the queue then make cfqq=NULL. Otherwise select_queue()
  will return a valid cfqq and cfq_dispatch_request() can hit following
  BUG_ON().

  BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list))

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-10 19:25:41 +01:00
Gui Jianfeng
554554f60a cfq: Remove wait_request flag when idle time is being deleted
Remove wait_request flag when idle time is being deleted, otherwise
it'll hit this path every time when a request is enqueued.

Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-10 09:38:39 +01:00
Corrado Zoccolo
edc71131c4 cfq-iosched: commenting non-obvious initialization
Added a comment to explain the initialization of last_delayed_sync.

Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-09 20:56:04 +01:00
Vivek Goyal
7667aa0630 cfq-iosched: Take care of corner cases of group losing share due to deletion
If there is a sequential reader running in a group, we wait for next request
to come in that group after slice expiry and once new request is in, we expire
the queue. Otherwise we delete the group from service tree and group looses
its fair share.

So far I was marking a queue as wait_busy if it had consumed its slice and
it was last queue in the group. But this condition did not cover following
two cases.

1.If a request completed and slice has not expired yet. Next request comes
  in and is dispatched to disk. Now select_queue() hits and slice has expired.
  This group will be deleted. Because request is still in the disk, this queue
  will never get a chance to wait_busy.

2.If request completed and slice has not expired yet. Before next request
  comes in (delay due to think time), select_queue() hits and expires the
  queue hence group. This queue never got a chance to wait busy.

Gui was hitting the boundary condition 1 and not getting fairness numbers
proportional to weight.

This patch puts the checks for above two conditions and improves the fairness
numbers for sequential workload on rotational media. Check in select_queue()
takes care of case 1 and additional check in should_wait_busy() takes care
of case 2.

Reported-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-09 15:11:04 +01:00
Vivek Goyal
c244bb50a9 cfq-iosched: Get rid of cfqq wait_busy_done flag
o Get rid of wait_busy_done flag. This flag only tells we were doing wait
  busy on a queue and that queue got request so expire it. That information
  can easily be obtained by (cfq_cfqq_wait_busy() && queue_is_not_empty). So
  remove this flag and keep code simple.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-09 15:11:03 +01:00
Gui Jianfeng
b9d8f4c73b cfq: Optimization for close cooperating queue searching
It doesn't make any sense to try to find out a close cooperating
queue if current cfqq is the only one in the group.

Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-09 15:11:03 +01:00
Corrado Zoccolo
573412b295 cfq-iosched: reduce write depth only if sync was delayed
The introduction of ramp-up formula for async queue depths has
slowed down dirty page reclaim, by reducing async write performance.
This patch makes sure the formula kicks in only when sync request
was recently delayed.

Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-09 12:32:55 +01:00
Vivek Goyal
878eaddd05 cfq-iosched: Do not access cfqq after freeing it
Fix a crash during boot reported by Jeff Moyer. Fix the issue of accessing
cfqq after freeing it.

Reported-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <axboe@carl.(none)>
2009-12-07 19:37:15 +01:00
Jens Axboe
bb729bc98c cfq-iosched: use call_rcu() instead of doing grace period stall on queue exit
After the merge of the IO controller patches, booting on my megaraid
box ran much slower. Vivek Goyal traced it down to megaraid discovery
creating tons of devices, each suffering a grace period when they later
kill that queue (if no device is found).

So lets use call_rcu() to batch these deferred frees, instead of taking
the grace period hit for each one.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-06 09:54:19 +01:00
Vivek Goyal
3e25206689 blkio: Implement dynamic io controlling policy registration
o One of the goals of block IO controller is that it should be able to
  support mulitple io control policies, some of which be operational at
  higher level in storage hierarchy.

o To begin with, we had one io controlling policy implemented by CFQ, and
  I hard coded the CFQ functions called by blkio. This created issues when
  CFQ is compiled as module.

o This patch implements a basic dynamic io controlling policy registration
  functionality in blkio. This is similar to elevator functionality where
  ioschedulers register the functions dynamically.

o Now in future, when more IO controlling policies are implemented, these
  can dynakically register with block IO controller.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-04 16:38:14 +01:00
Vivek Goyal
9d6a986c0b blkio: Export some symbols from blkio as its user CFQ can be a module
o blkio controller is inside the kernel and cfq makes use of interfaces
  exported by blkio. CFQ can be a module too, hence export symbols used
  by CFQ.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-04 16:38:14 +01:00
Shaohua Li
3c764b7a65 cfq-iosched: make nonrot check logic consistent
cfq_arm_slice_timer() has logic to disable idle window for SSD device. The same
thing should be done at cfq_select_queue() too, otherwise we will still see
idle window. This makes the nonrot check logic consistent in cfq.
Tests in a intel SSD with low_latency knob close, below patch can triple disk
thoughput for muti-thread sequential read.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-04 13:12:06 +01:00
Jens Axboe
f2eecb9152 cfq-iosched: move IO controller declerations to a header file
They should not be declared inside some other file that's not related
to CFQ.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-04 10:06:35 +01:00
Vivek Goyal
c04645e592 blkio: Wait on sync-noidle queue even if rq_noidle = 1
o rq_noidle() is supposed to tell cfq that do not expect a request after this
  one, hence don't idle. But this does not seem to work very well. For example
  for direct random readers, rq_noidle = 1 but there is next request coming
  after this. Not idling, leads to a group not getting its share even if
  group_isolation=1.

o The right solution for this issue is to scan the higher layers and set
  right flag (WRITE_SYNC or WRITE_ODIRECT). For the time being, this single
  line fix helps. This should not have any significant impact when we are
  not using cgroups. I will later figure out IO paths in higher layer and
  fix it.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-03 19:28:53 +01:00
Vivek Goyal
ae30c28655 blkio: Implement group_isolation tunable
o If a group is running only a random reader, then it will not have enough
  traffic to keep disk busy and we will reduce overall throughput. This
  should result in better latencies for random reader though. If we don't
  idle on random reader service tree, then this random reader will experience
  large latencies if there are other groups present in system with sequential
  readers running in these.

o One solution suggested by corrado is that by default keep the random readers
  or sync-noidle workload in root group so that during one dispatch round
  we idle only once on sync-noidle tree. This means that all the sync-idle
  workload queues will be in their respective group and we will see service
  differentiation in those but not on sync-noidle workload.

o Provide a tunable group_isolation. If set, this will make sure that even
  sync-noidle queues go in their respective group and we wait on these. This
  provides stronger isolation between groups but at the expense of throughput
  if group does not have enough traffic to keep the disk busy.

o By default group_isolation = 0

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-03 19:28:53 +01:00
Vivek Goyal
f26bd1f0a3 blkio: Determine async workload length based on total number of queues
o Async queues are not per group. Instead these are system wide and maintained
  in root group. Hence their workload slice length should be calculated
  based on total number of queues in the system and not just queues in the
  root group.

o As root group's default weight is 1000, make sure to charge async queue
  more in terms of vtime so that it does not get more time on disk because
  root group has higher weight.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-03 19:28:53 +01:00
Vivek Goyal
f75edf2dc8 blkio: Wait for cfq queue to get backlogged if group is empty
o If a queue consumes its slice and then gets deleted from service tree, its
  associated group will also get deleted from service tree if this was the
  only queue in the group. That will make group loose its share.

o For the queues on which we have idling on and if these have used their
  slice, wait a bit for these queues to get backlogged again and then
  expire these queues so that group does not loose its share.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-03 19:28:53 +01:00
Vivek Goyal
f8d461d692 blkio: Propagate cgroup weight updation to cfq groups
o Propagate blkio cgroup weight updation to associated cfq groups.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-03 19:28:53 +01:00
Vivek Goyal
24610333d5 blkio: Drop the reference to queue once the task changes cgroup
o If a task changes cgroup, drop reference to the cfqq associated with io
  context and set cfqq pointer stored in ioc to NULL so that upon next request
  arrival we will allocate a  new queue in new group.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-03 19:28:52 +01:00
Vivek Goyal
8682e1f15f blkio: Provide some isolation between groups
o Do not allow following three operations across groups for isolation.
	- selection of co-operating queues
	- preemtpions across groups
	- request merging across groups.

o Async queues are currently global and not per group. Allow preemption of
  an async queue if a sync queue in other group gets backlogged.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-03 19:28:52 +01:00
Vivek Goyal
220841906f blkio: Export disk time and sectors used by a group to user space
o Export disk time and sector used by a group to user space through cgroup
  interface.

o Also export a "dequeue" interface to cgroup which keeps track of how many
  a times a group was deleted from service tree. Helps in debugging.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-03 19:28:52 +01:00
Vivek Goyal
2868ef7b39 blkio: Some debugging aids for CFQ
o Some debugging aids for CFQ.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-03 19:28:52 +01:00
Vivek Goyal
b1c3576961 blkio: Take care of cgroup deletion and cfq group reference counting
o One can choose to change elevator or delete a cgroup. Implement group
  reference counting so that both elevator exit and cgroup deletion can
  take place gracefully.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Nauman Rafique <nauman@google.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-03 19:28:52 +01:00
Vivek Goyal
25fb5169d4 blkio: Dynamic cfq group creation based on cgroup tasks belongs to
o Determine the cgroup IO submitting task belongs to and create the cfq
  group if it does not exist already.

o Also link cfqq and associated cfq group.

o Currently all async IO is mapped to root group.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-03 19:28:52 +01:00
Vivek Goyal
dae739ebc4 blkio: Group time used accounting and workload context save restore
o This patch introduces the functionality to do the accounting of group time
  when a queue expires. This time used decides which is the group to go
  next.

o Also introduce the functionlity to save and restore the workload type
  context with-in group. It might happen that once we expire the cfq queue
  and group, a different group will schedule in and we will lose the context
  of the workload type. Hence save and restore it upon queue expiry.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-03 19:28:52 +01:00
Vivek Goyal
58ff82f34c blkio: Implement per cfq group latency target and busy queue avg
o So far we had 300ms soft target latency system wide. Now with the
  introduction of cfq groups, divide that latency by number of groups so
  that one can come up with group target latency which will be helpful
  in determining the workload slice with-in group and also the dynamic
  slice length of the cfq queue.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-03 19:28:52 +01:00
Vivek Goyal
25bc6b0776 blkio: Introduce per cfq group weights and vdisktime calculations
o Bring in the per cfq group weight and how vdisktime is calculated for the
  group. Also bring in the functionality of updating the min_vdisktime of
  the group service tree.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-03 19:28:52 +01:00
Vivek Goyal
1fa8f6d68b blkio: Introduce the root service tree for cfq groups
o So far we just had one cfq_group in cfq_data. To create space for more than
  one cfq_group, we need to have a service tree of groups where all the groups
  can be queued if they have active cfq queues backlogged in these.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-03 19:28:51 +01:00
Vivek Goyal
f04a642463 blkio: Keep queue on service tree until we expire it
o Currently cfqq deletes a queue from service tree if it is empty (even if
  we might idle on the queue). This patch keeps the queue on service tree
  hence associated group remains on the service tree until we decide that
  we are not going to idle on the queue and expire it.

o This just helps in time accounting for queue/group and in implementation
  of rest of the patches.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-03 19:28:51 +01:00
Vivek Goyal
615f0259e6 blkio: Implement macro to traverse each service tree in group
o Implement a macro to traverse each service tree in the group. This avoids
  usage of double for loop and special condition for idle tree 4 times.

o Macro is little twisted because of special handling of idle class service
  tree.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-03 19:28:51 +01:00
Vivek Goyal
cdb16e8f73 blkio: Introduce the notion of cfq groups
o This patch introduce the notion of cfq groups. Soon we will can have multiple
  groups of different weights in the system.

o Various service trees (prioclass and workload type trees), will become per
  cfq group. So hierarchy looks as follows.

			cfq_groups
			   |
			workload type
			   |
		        cfq queue

o When an scheduling decision has to be taken, first we select the cfq group
  then workload with-in the group and then cfq queue with-in the workload
  type.

o This patch just makes various workload service tree per cfq group and
  introduce the function to be able to choose a group for scheduling.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-03 19:28:51 +01:00
Vivek Goyal
bf79193710 blkio: Set must_dispatch only if we decided to not dispatch the request
o must_dispatch flag should be set only if we decided not to run the queue
  and dispatch the request.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-03 19:28:51 +01:00
Shaohua Li
474b18ccc2 cfq-iosched: no dispatch limit for single queue
Since commit 2f5cb7381b, each queue can send
up to 4 * 4 requests if only one queue exists. I wonder why we have such limit.
Device supports tag can send more requests. For example, AHCI can send 31
requests. Test (direct aio randread) shows the limits reduce about 4% disk
thoughput.
On the other hand, since we send one request one time, if other queue
pop when current is sending more than cfq_quantum requests, current queue will
stop send requests soon after one request, so sounds there is no big latency.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-12-03 12:58:05 +01:00
Jens Axboe
464191c65b Revert "cfq: Make use of service count to estimate the rb_key offset"
This reverts commit 3586e917f2.

Corrado Zoccolo <czoccolo@gmail.com> correctly points out, that we need
consistency of rb_key offset across groups. This means we cannot properly
use the per-service_tree service count. Revert this change.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-11-30 09:38:13 +01:00
Corrado Zoccolo
8e550632cc cfq-iosched: fix corner cases in idling logic
Idling logic was disabled in some corner cases, leading to unfair share
 for noidle queues.
 * the idle timer was not armed if there were other requests in the
   driver. unfortunately, those requests could come from other workloads,
   or queues for which we don't enable idling. So we will check only
   pending requests from the active queue
 * rq_noidle check on no-idle queue could disable the end of tree idle if
   the last completed request was rq_noidle. Now, we will disable that
   idle only if all the queues served in the no-idle tree had rq_noidle
   requests.

Reported-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-11-26 10:39:31 +01:00
Corrado Zoccolo
76280aff1c cfq-iosched: idling on deep seeky sync queues
Seeky sync queues with large depth can gain unfairly big share of disk
 time, at the expense of other seeky queues. This patch ensures that
 idling will be enabled for queues with I/O depth at least 4, and small
 think time. The decision to enable idling is sticky, until an idle
 window times out without seeing a new request.

The reasoning behind the decision is that, if an application is using
large I/O depth, it is already optimized to make full utilization of
the hardware, and therefore we reserve a slice of exclusive use for it.

Reported-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-11-26 10:39:31 +01:00
Corrado Zoccolo
e4a229196a cfq-iosched: fix no-idle preemption logic
An incoming no-idle queue should preempt the active no-idle queue
 only if the active queue is idling due to service tree empty.
 Previous code was buggy in two ways:
 * it relied on service_tree field to be set on the active queue, while
   it is not set when the code is idling for a new request
 * it didn't check for the service tree empty condition, so could lead to
   LIFO behaviour if multiple queues with depth > 1 were preempting each
   other on an non-NCQ device.

Reported-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-11-26 10:39:31 +01:00
Corrado Zoccolo
e459dd08f4 cfq-iosched: fix ncq detection code
CFQ's detection of queueing devices initially assumes a queuing device
and detects if the queue depth reaches a certain threshold.
However, it will reconsider this choice periodically.

Unfortunately, if device is considered not queuing, CFQ will force a
unit queue depth for some workloads, thus defeating the detection logic.
This leads to poor performance on queuing hardware,
since the idle window remains enabled.

Given this premise, switching to hw_tag = 0 after we have proved at
least once that the device is NCQ capable is not a good choice.

The new detection code starts in an indeterminate state, in which CFQ behaves
as if hw_tag = 1, and then, if for a long observation period we never saw
large depth, we switch to hw_tag = 0, otherwise we stick to hw_tag = 1,
without reconsidering it again.

Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-11-26 10:02:57 +01:00
Corrado Zoccolo
c16632bab1 cfq-iosched: cleanup unreachable code
cfq_should_idle returns false for no-idle queues that are not the last,
so the control flow will never reach the removed code in a state that
satisfies the if condition.
The unreachable code was added to emulate previous cfq behaviour for
non-NCQ rotational devices. My tests show that even without it, the
performances and fairness are comparable with previous cfq, thanks to
the fact that all seeky queues are grouped together, and that we idle at
the end of the tree.

Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-11-26 09:46:46 +01:00
Gui Jianfeng
3586e917f2 cfq: Make use of service count to estimate the rb_key offset
For the moment, different workload cfq queues are put into different
service trees. But CFQ still uses "busy_queues" to estimate rb_key
offset when inserting a cfq queue into a service tree. I think this
isn't appropriate, and it should make use of service tree count to do
this estimation. This patch is for for-2.6.33 branch.

Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-11-26 09:14:11 +01:00
Randy Dunlap
ad5ebd2fa2 block: jiffies fixes
Use HZ-independent calculation of milliseconds.
Add jiffies.h where it was missing since functions or macros
from it are used.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-11-11 13:47:45 +01:00
Corrado Zoccolo
cf7c25cf91 cfq-iosched: fix next_rq computation
Cfq has a bug in computation of next_rq, that affects transition
between multiple sequential request streams in a single queue
(e.g.: two sequential buffered writers of the same priority),
causing the alternation between the two streams for a transient period.

  8,0    1    18737     0.260400660  5312  D   W 141653311 + 256
  8,0    1    20839     0.273239461  5400  D   W 141653567 + 256
  8,0    1    20841     0.276343885  5394  D   W 142803919 + 256
  8,0    1    20843     0.279490878  5394  D   W 141668927 + 256
  8,0    1    20845     0.292459993  5400  D   W 142804175 + 256
  8,0    1    20847     0.295537247  5400  D   W 141668671 + 256
  8,0    1    20849     0.298656337  5400  D   W 142804431 + 256
  8,0    1    20851     0.311481148  5394  D   W 141668415 + 256
  8,0    1    20853     0.314421305  5394  D   W 142804687 + 256
  8,0    1    20855     0.318960112  5400  D   W 142804943 + 256

The fix makes sure that the next_rq is computed from the last
dispatched request, and not affected by merging.

  8,0    1    37776     4.305161306     0  D   W 141738087 + 256
  8,0    1    37778     4.308298091     0  D   W 141738343 + 256
  8,0    1    37780     4.312885190     0  D   W 141738599 + 256
  8,0    1    37782     4.315933291     0  D   W 141738855 + 256
  8,0    1    37784     4.319064459     0  D   W 141739111 + 256
  8,0    1    37786     4.331918431  5672  D   W 142803007 + 256
  8,0    1    37788     4.334930332  5672  D   W 142803263 + 256
  8,0    1    37790     4.337902723  5672  D   W 142803519 + 256
  8,0    1    37792     4.342359774  5672  D   W 142803775 + 256
  8,0    1    37794     4.345318286     0  D   W 142804031 + 256

Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-11-08 17:16:46 +01:00
Jens Axboe
e00ef79971 cfq-iosched: get rid of the coop_preempt flag
We need to rework this logic post the cooperating cfq_queue merging,
for now just get rid of it and Jeff Moyer will fix the fall out.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-11-04 08:54:55 +01:00
Jens Axboe
125c4f221a cfq-iosched: fix merge error
We ended up with testing the same condition twice, pretty
pointless. Remove that first if.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-11-03 21:25:45 +01:00
Jens Axboe
2058297d2d Merge branch 'for-linus' into for-2.6.33
Conflicts:
	block/cfq-iosched.c

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-11-03 21:14:39 +01:00
Jens Axboe
150e6c67f4 Merge branch 'cfq-2.6.33' into for-2.6.33 2009-11-03 21:12:10 +01:00
Shaohua Li
4b27e1bb44 cfq-iosched: limit coop preemption
CFQ has an optimization for cooperated applications. if several
io-context have close requests, they will get boost. But the
optimization get abused. Considering thread a, b, which work on one
file. a reads sectors s, s+2, s+4, ...; b reads sectors s+1, s+3, s
+5, ... Both a and b are sequential read, so they can open idle window.
a reads a sector s and goes to idle window and wakeup b. b reads sector
s+1, since in current implementation, cfq_should_preempt() thinks a and
b are cooperators, b will preempt a. b then reads sector s+1 and goes to
idle window and wakeup a. for the same reason, a will preempt b and
reads s+2. a and b will continue the circle. The circle will be very
long, and a and b will occupy whole disk queue. Other applications will
nearly have no chance to run.

Fix this limiting coop preempt until a queue is scheduled normally
again.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-11-03 20:25:02 +01:00
Jens Axboe
e6ec4fe245 cfq-iosched: fix bad return value cfq_should_preempt()
Commit a6151c3a5c inadvertently reversed
a preempt condition check, potentially causing a performance regression.
Make the meta check correct again.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-11-03 20:21:35 +01:00
Corrado Zoccolo
dddb74519a cfq-iosched: simplify prio-unboost code
Eliminate redundant checks.

Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-11-02 10:40:37 +01:00
Jens Axboe
5869619cb5 cfq-iosched: fix style issue in cfq_get_avg_queues()
Line breaks and bad brace placement.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-28 09:27:07 +01:00
Corrado Zoccolo
718eee0579 cfq-iosched: fairness for sync no-idle queues
Currently no-idle queues in cfq are not serviced fairly:
even if they can only dispatch a small number of requests at a time,
they have to compete with idling queues to be serviced, experiencing
large latencies.

We should notice, instead, that no-idle queues are the ones that would
benefit most from having low latency, in fact they are any of:
* processes with large think times (e.g. interactive ones like file
  managers)
* seeky (e.g. programs faulting in their code at startup)
* or marked as no-idle from upper levels, to improve latencies of those
  requests.

This patch improves the fairness and latency for those queues, by:
* separating sync idle, sync no-idle and async queues in separate
  service_trees, for each priority
* service all no-idle queues together
* and idling when the last no-idle queue has been serviced, to
  anticipate for more no-idle work
* the timeslices allotted for idle and no-idle service_trees are
  computed proportionally to the number of processes in each set.

Servicing all no-idle queues together should have a performance boost
for NCQ-capable drives, without compromising fairness.

Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-28 09:23:26 +01:00
Corrado Zoccolo
a6d44e982d cfq-iosched: enable idling for last queue on priority class
cfq can disable idling for queues in various circumstances.
When workloads of different priorities are competing, if the higher
priority queue has idling disabled, lower priority queues may steal
its disk share. For example, in a scenario with an RT process
performing seeky reads vs a BE process performing sequential reads,
on an NCQ enabled hardware, with low_latency unset,
the RT process will dispatch only the few pending requests every full
slice of service for the BE process.

The patch solves this issue by always performing idle on the last
queue at a given priority class > idle. If the same process, or one
that can pre-empt it (so at the same priority or higher), submits a
new request within the idle window, the lower priority queue won't
dispatch, saving the disk bandwidth for higher priority ones.

Note: this doesn't touch the non_rotational + NCQ case (no hardware
to test if this is a benefit in that case).

Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-28 09:23:26 +01:00
Corrado Zoccolo
c0324a020e cfq-iosched: reimplement priorities using different service trees
We use different service trees for different priority classes.
This allows a simplification in the service tree insertion code, that no
longer has to consider priority while walking the tree.

Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-28 09:23:26 +01:00
Corrado Zoccolo
aa6f6a3de1 cfq-iosched: preparation to handle multiple service trees
We embed a pointer to the service tree in each queue, to handle multiple
service trees easily.
Service trees are enriched with a counter.
cfq_add_rq_rb is invoked after putting the rq in the fifo, to ensure
that all fields in rq are properly initialized.

Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-28 09:23:26 +01:00
Corrado Zoccolo
5db5d64277 cfq-iosched: adapt slice to number of processes doing I/O
When the number of processes performing I/O concurrently increases,
a fixed time slice per process will cause large latencies.

This patch, if low_latency mode is enabled,  will scale the time slice
assigned to each process according to a 300ms target latency.

In order to keep fairness among processes:
* The number of active processes is computed using a special form of
running average, that quickly follows sudden increases (to keep latency low),
and decrease slowly (to have fairness in spite of rapid decreases of this
value).

To safeguard sequential bandwidth, we impose a minimum time slice
(computed using 2*cfq_slice_idle as base, adjusted according to priority
and async-ness).

Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-28 09:23:26 +01:00
Shaohua Li
1a1238a7dd cfq-iosched: improve hw_tag detection
If active queue hasn't enough requests and idle window opens, cfq will not
dispatch sufficient requests to hardware. In such situation, current code
will zero hw_tag. But this is because cfq doesn't dispatch enough requests
instead of hardware queue doesn't work. Don't zero hw_tag in such case.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-27 08:46:23 +01:00
Jeff Moyer
e6c5bc737a cfq: break apart merged cfqqs if they stop cooperating
cfq_queues are merged if they are issuing requests within the mean seek
distance of one another.  This patch detects when the coopearting stops and
breaks the queues back up.

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-26 14:34:47 +01:00
Jeff Moyer
b3b6d0408c cfq: change the meaning of the cfqq_coop flag
The flag used to indicate that a cfqq was allowed to jump ahead in the
scheduling order due to submitting a request close to the queue that
just executed.  Since closely cooperating queues are now merged, the flag
holds little meaning.  Change it to indicate that multiple queues were
merged.  This will later be used to allow the breaking up of merged queues
when they are no longer cooperating.

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-26 14:34:47 +01:00
Jeff Moyer
df5fe3e8e1 cfq: merge cooperating cfq_queues
When cooperating cfq_queues are detected currently, they are allowed to
skip ahead in the scheduling order.  It is much more efficient to
automatically share the cfq_queue data structure between cooperating processes.
Performance of the read-test2 benchmark (which is written to emulate the
dump(8) utility) went from 12MB/s to 90MB/s on my SATA disk.  NFS servers
with multiple nfsd threads also saw performance increases.

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-26 14:34:47 +01:00
Jeff Moyer
b2c18e1e08 cfq: calculate the seek_mean per cfq_queue not per cfq_io_context
async cfq_queue's are already shared between processes within the same
priority, and forthcoming patches will change the mapping of cic to sync
cfq_queue from 1:1 to 1:N.  So, calculate the seekiness of a process
based on the cfq_queue instead of the cfq_io_context.

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-26 14:34:46 +01:00
Corrado Zoccolo
355b659c87 cfq-iosched: avoid probable slice overrun when idling
If the average think time is larger than the remaining time slice
for any given queue, don't allow it to idle. A succesful idle also
means that we need to dispatch and complete a request, so if we don't
even have time left for the idle process, we would overrun the slice
in any case.

Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-08 08:43:32 +02:00
Jens Axboe
a6151c3a5c cfq-iosched: apply bool value where we return 0/1
Saves 16 bytes of text, woohoo. But the more important point is
that it makes the code more readable when returning bool for 0/1
cases.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-07 20:02:57 +02:00
Corrado Zoccolo
ec60e4f674 cfq-iosched: fix think time allowed for seekers
CFQ enables idle only for processes that think less than the allowed
idle time. Since idle time is lower for seeky queues, we should use the
correct value in the comparison.

Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-07 19:51:54 +02:00
Jens Axboe
b9c8946b19 cfq-iosched: fix the slice residual sign
We should subtract the slice residual from the rb tree key, since
a negative residual count indicates that the cfqq overran its slice
the last time. Hence we want to add the overrun time, to position
it a bit further away in the service tree.

Reported-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-06 21:09:32 +02:00
Jens Axboe
0b182d617e cfq-iosched: abstract out the 'may this cfqq dispatch' logic
Makes the whole thing easier to read, cfq_dispatch_requests() was
a bit messy before.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-06 20:49:37 +02:00
Jens Axboe
23e018a1b0 block: get rid of kblock_schedule_delayed_work()
It was briefly introduced to allow CFQ to to delayed scheduling,
but we ended up removing that feature again. So lets kill the
function and export, and just switch CFQ back to the normal work
schedule since it is now passing in a '0' delay from all call
sites.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-05 11:03:58 +02:00
Corrado Zoccolo
48e025e63a cfq-iosched: fix possible problem with jiffies wraparound
The RR service tree is indexed by a key that is relative to current jiffies.
This can cause problems on jiffies wraparound.

The patch fixes it using time_before comparison, and changing
the add_front path to use a relative number, too.

Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-05 11:03:55 +02:00
Jens Axboe
30996f40bf cfq-iosched: fix issue with rq-rq merging and fifo list ordering
cfq uses rq->start_time as the fifo indicator, but that field may
get modified prior to cfq doing it's fifo list adjustment when
a request gets merged with another request. This can cause the
fifo list to become unordered.

Reported-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-05 11:03:39 +02:00
Jens Axboe
e00c54c36a cfq-iosched: don't delay async queue if it hasn't dispatched at all
We cannot delay for the first dispatch of the async queue if it
hasn't dispatched at all, since that could present a local user
DoS attack vector using an app that just did slow timed sync reads
while filling memory.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-04 20:36:19 +02:00
Jens Axboe
61f0c1dcaa cfq-iosched: use assigned slice sync value, not default
We should use the sysfs modified slice sync value, in case it differs
from the default.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-03 19:46:03 +02:00
Jens Axboe
963b72fc66 cfq-iosched: rename 'desktop' sysfs entry to 'low_latency'
Don't think that's necessarily a perfect description of what this
option fiddles with, but it's probably better than 'desktop'.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-03 19:42:18 +02:00
Jens Axboe
8e29675555 cfq-iosched: implement slower async initiate and queue ramp up
This slowly ramps up the async queue depth based on the time
passed since the sync IO, and doesn't allow async at all until
a sync slice period has passed.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-03 16:27:13 +02:00
Vivek Goyal
365722bb91 cfq-iosched: delay async IO dispatch, if sync IO was just done
o Do not allow more than max_dispatch requests from an async queue, if some
  sync request has finished recently. This is in the hope that sync activity
  is still going on in the system and we might receive a sync request soon.
  Most likely from a sync queue which finished a request and we did not enable
  idling on it.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-03 15:21:27 +02:00
Jens Axboe
1d2235152d cfq-iosched: add a knob for desktop interactiveness
This is basically identical to what Vivek Goyal posted, but combined
into one and labelled 'desktop' instead of 'fairness'. The goal
is to continue to improve on the latency side of things as it relates
to interactiveness, keeping the questionable bits under this sysfs
tunable so it would be easy for throughput-only people to turn off.

Apart from adding the interactive sysfs knob, it also adds the
behavioural change of allowing slice idling even if the hardware
does tagged command queuing.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-10-02 20:06:02 +02:00
Linus Torvalds
ada3fa1505 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: (46 commits)
  powerpc64: convert to dynamic percpu allocator
  sparc64: use embedding percpu first chunk allocator
  percpu: kill lpage first chunk allocator
  x86,percpu: use embedding for 64bit NUMA and page for 32bit NUMA
  percpu: update embedding first chunk allocator to handle sparse units
  percpu: use group information to allocate vmap areas sparsely
  vmalloc: implement pcpu_get_vm_areas()
  vmalloc: separate out insert_vmalloc_vm()
  percpu: add chunk->base_addr
  percpu: add pcpu_unit_offsets[]
  percpu: introduce pcpu_alloc_info and pcpu_group_info
  percpu: move pcpu_lpage_build_unit_map() and pcpul_lpage_dump_cfg() upward
  percpu: add @align to pcpu_fc_alloc_fn_t
  percpu: make @dyn_size mandatory for pcpu_setup_first_chunk()
  percpu: drop @static_size from first chunk allocators
  percpu: generalize first chunk allocator selection
  percpu: build first chunk allocators selectively
  percpu: rename 4k first chunk allocator to page
  percpu: improve boot messages
  percpu: fix pcpu_reclaim() locking
  ...

Fix trivial conflict as by Tejun Heo in kernel/sched.c
2009-09-15 09:39:44 -07:00
Jeff Moyer
06d2188644 cfq: choose a new next_req when a request is dispatched
This patch addresses http://bugzilla.kernel.org/show_bug.cgi?id=13401, a
regression introduced in 2.6.30.

From the bug report:

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-09-14 08:24:52 +02:00
Shan Wei
b217a903ab cfq: fix the log message after dispatched a request
The blktrace tools can show process id when cfq dispatched a request,
using cfq_log_cfqq() instead of cfq_log().

Signed-off-by: Shan Wei <shanwei@cn.fujitsu.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-09-11 14:34:33 +02:00
Jens Axboe
1b379d8daf cfq-iosched: get rid of must_alloc flag
It's not currently used, as pointed out by
Gui Jianfeng <guijianfeng@cn.fujitsu.com>. We already check the
wait_request flag to allow an idling queue priority allocation access,
so we don't need this extra flag.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-09-11 14:33:32 +02:00
Jens Axboe
1f98a13f62 bio: first step in sanitizing the bio->bi_rw flag testing
Get rid of any functions that test for these bits and make callers
use bio_rw_flagged() directly. Then it is at least directly apparent
what variable and flag they check.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-09-11 14:33:31 +02:00
Vivek Goyal
d58b85e1e8 cfq-iosched: no need to keep track of busy_rt_queues
o Get rid of busy_rt_queues infrastructure. Looks like it is redundant.

o Once an RT queue gets request it will preempt any of the BE or IDLE queues
  immediately. Otherwise this queue will be put on service tree and scheduler
  will anyway select this queue before any of the BE or IDLE queue. Hence
  looks like there is no need to keep track of how many busy RT queues are
  currently on service tree.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-09-11 14:33:30 +02:00
Jens Axboe
5ad531db6e cfq-iosched: drain device queue before switching to a sync queue
To lessen the impact of async IO on sync IO, let the device drain of
any async IO in progress when switching to a sync cfqq that has idling
enabled.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-09-11 14:33:30 +02:00
Tejun Heo
384be2b18a Merge branch 'percpu-for-linus' into percpu-for-next
Conflicts:
	arch/sparc/kernel/smp_64.c
	arch/x86/kernel/cpu/perf_counter.c
	arch/x86/kernel/setup_percpu.c
	drivers/cpufreq/cpufreq_ondemand.c
	mm/percpu.c

Conflicts in core and arch percpu codes are mostly from commit
ed78e1e078dd44249f88b1dd8c76dafb39567161 which substituted many
num_possible_cpus() with nr_cpu_ids.  As for-next branch has moved all
the first chunk allocators into mm/percpu.c, the changes are moved
from arch code to mm/percpu.c.

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-08-14 14:45:31 +09:00
Vivek Goyal
32f2e807a3 cfq-iosched: reset oom_cfqq in cfq_set_request()
In case memory is scarce, we now default to oom_cfqq. Once memory is
available again, we should allocate a new cfqq and stop using oom_cfqq for
a particular io context.

Once a new request comes in, check if we are using oom_cfqq, and if yes,
try to allocate a new cfqq.

Tested the patch by forcing the use of oom_cfqq and upon next request thread
realized that it was using oom_cfqq and it allocated a new cfqq.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-07-10 20:31:54 +02:00
Tejun Heo
c43768cbb7 Merge branch 'master' into for-next
Pull linus#master to merge PER_CPU_DEF_ATTRIBUTES and alpha build fix
changes.  As alpha in percpu tree uses 'weak' attribute instead of
inline assembly, there's no need for __used attribute.

Conflicts:
	arch/alpha/include/asm/percpu.h
	arch/mn10300/kernel/vmlinux.lds.S
	include/linux/percpu-defs.h
2009-07-04 07:13:18 +09:00
Shan Wei
b706f64281 cfq-iosched: remove redundant check for NULL cfqq in cfq_set_request()
With the changes for falling back to an oom_cfqq, we never fail
to find/allocate a queue in cfq_get_queue(). So remove the check.

Signed-off-by: Shan Wei <shanwei@cn.fujitsu.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-07-01 12:41:14 +02:00
Jens Axboe
6118b70b3a cfq-iosched: get rid of the need for __GFP_NOFAIL in cfq_find_alloc_queue()
Setup an emergency fallback cfqq that we allocate at IO scheduler init
time. If the slab allocation fails in cfq_find_alloc_queue(), we'll just
punt IO to that cfqq instead. This ensures that cfq_find_alloc_queue()
never fails without having to ensure free memory.

On cfqq lookup, always try to allocate a new cfqq if the given cfq io
context has the oom_cfqq assigned. This ensures that we only temporarily
punt to this shared queue.

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-07-01 10:56:25 +02:00
Jens Axboe
d5036d770f cfq-iosched: move cfqq initialization out of cfq_find_alloc_queue()
We're going to be needing that init code outside of that function
to get rid of the __GFP_NOFAIL in cfqq allocation.

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-07-01 10:56:25 +02:00
Tejun Heo
245b2e70ea percpu: clean up percpu variable definitions
Percpu variable definition is about to be updated such that all percpu
symbols including the static ones must be unique.  Update percpu
variable definitions accordingly.

* as,cfq: rename ioc_count uniquely

* cpufreq: rename cpu_dbs_info uniquely

* xen: move nesting_count out of xen_evtchn_do_upcall() and rename it

* mm: move ratelimits out of balance_dirty_pages_ratelimited_nr() and
  rename it

* ipv4,6: rename cookie_scratch uniquely

* x86 perf_counter: rename prev_left to pmc_prev_left, irq_entry to
  pmc_irq_entry and nmi_entry to pmc_nmi_entry

* perf_counter: rename disable_count to perf_disable_count

* ftrace: rename test_event_disable to ftrace_test_event_disable

* kmemleak: rename test_pointer to kmemleak_test_pointer

* mce: rename next_interval to mce_next_interval

[ Impact: percpu usage cleanups, no duplicate static percpu var names ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: linux-mm <linux-mm@kvack.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <srostedt@redhat.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Andi Kleen <andi@firstfloor.org>
2009-06-24 15:13:48 +09:00
Jeff Moyer
6923715ae3 cfq: remove extraneous '\n' in blktrace output
I noticed a blank line in blktrace output.  This patch fixes that.

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-06-16 08:21:04 +02:00
Gui Jianfeng
81be834713 cfq: cleanup for last_end_request in cfq_data
Actually, last_end_request in cfq_data isn't used now. So lets
just remove it.

Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-06-16 08:21:03 +02:00
Nikanth Karthikesan
d9c7d394a8 block: prevent possible io_context->refcount overflow
Currently io_context has an atomic_t(32-bit) as refcount.  In the case of
cfq, for each device against whcih a task does I/O, a reference to the
io_context would be taken.  And when there are multiple process sharing
io_contexts(CLONE_IO) would also have a reference to the same io_context.

Theoretically the possible maximum number of processes sharing the same
io_context + the number of disks/cfq_data referring to the same io_context
can overflow the 32-bit counter on a very high-end machine.

Even though it is an improbable case, let us make it atomic_long_t.

Signed-off-by: Nikanth Karthikesan <knikanth@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-06-10 23:07:15 +02:00
Tejun Heo
2e46e8b27a block: drop request->hard_* and *nr_sectors
struct request has had a few different ways to represent some
properties of a request.  ->hard_* represent block layer's view of the
request progress (completion cursor) and the ones without the prefix
are supposed to represent the issue cursor and allowed to be updated
as necessary by the low level drivers.  The thing is that as block
layer supports partial completion, the two cursors really aren't
necessary and only cause confusion.  In addition, manual management of
request detail from low level drivers is cumbersome and error-prone at
the very least.

Another interesting duplicate fields are rq->[hard_]nr_sectors and
rq->{hard_cur|current}_nr_sectors against rq->data_len and
rq->bio->bi_size.  This is more convoluted than the hard_ case.

rq->[hard_]nr_sectors are initialized for requests with bio but
blk_rq_bytes() uses it only for !pc requests.  rq->data_len is
initialized for all request but blk_rq_bytes() uses it only for pc
requests.  This causes good amount of confusion throughout block layer
and its drivers and determining the request length has been a bit of
black magic which may or may not work depending on circumstances and
what the specific LLD is actually doing.

rq->{hard_cur|current}_nr_sectors represent the number of sectors in
the contiguous data area at the front.  This is mainly used by drivers
which transfers data by walking request segment-by-segment.  This
value always equals rq->bio->bi_size >> 9.  However, data length for
pc requests may not be multiple of 512 bytes and using this field
becomes a bit confusing.

In general, having multiple fields to represent the same property
leads only to confusion and subtle bugs.  With recent block low level
driver cleanups, no driver is accessing or manipulating these
duplicate fields directly.  Drop all the duplicates.  Now rq->sector
means the current sector, rq->data_len the current total length and
rq->bio->bi_size the current segment length.  Everything else is
defined in terms of these three and available only through accessors.

* blk_recalc_rq_sectors() is collapsed into blk_update_request() and
  now handles pc and fs requests equally other than rq->sector update.
  This means that now pc requests can use partial completion too (no
  in-kernel user yet tho).

* bio_cur_sectors() is replaced with bio_cur_bytes() as block layer
  now uses byte count as the primary data length.

* blk_rq_pos() is now guranteed to be always correct.  In-block users
  converted.

* blk_rq_bytes() is now guaranteed to be always valid as is
  blk_rq_sectors().  In-block users converted.

* blk_rq_sectors() is now guaranteed to equal blk_rq_bytes() >> 9.
  More convenient one is used.

* blk_rq_bytes() and blk_rq_cur_bytes() are now inlined and take const
  pointer to request.

[ Impact: API cleanup, single way to represent one property of a request ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-05-11 09:50:54 +02:00
Tejun Heo
83096ebf12 block: convert to pos and nr_sectors accessors
With recent cleanups, there is no place where low level driver
directly manipulates request fields.  This means that the 'hard'
request fields always equal the !hard fields.  Convert all
rq->sectors, nr_sectors and current_nr_sectors references to
accessors.

While at it, drop superflous blk_rq_pos() < 0 test in swim.c.

[ Impact: use pos and nr_sectors accessors ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Tested-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Tested-by: Adrian McMenamin <adrian@mcmen.demon.co.uk>
Acked-by: Adrian McMenamin <adrian@mcmen.demon.co.uk>
Acked-by: Mike Miller <mike.miller@hp.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Cc: Borislav Petkov <petkovbb@googlemail.com>
Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Eric Moore <Eric.Moore@lsi.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Pete Zaitcev <zaitcev@redhat.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Paul Clements <paul.clements@steeleye.com>
Cc: Tim Waugh <tim@cyberelk.net>
Cc: Jeff Garzik <jgarzik@pobox.com>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Alex Dubov <oakad@yahoo.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Dario Ballabio <ballabio_dario@emc.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: unsik Kim <donari75@gmail.com>
Cc: Laurent Vivier <Laurent@lvivier.info>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-05-11 09:50:54 +02:00
Tejun Heo
5b93629b45 block: implement blk_rq_pos/[cur_]sectors() and convert obvious ones
Implement accessors - blk_rq_pos(), blk_rq_sectors() and
blk_rq_cur_sectors() which return rq->hard_sector, rq->hard_nr_sectors
and rq->hard_cur_sectors respectively and convert direct references of
the said fields to the accessors.

This is in preparation of request data length handling cleanup.

Geert	: suggested adding const to struct request * parameter to accessors
Sergei	: spotted error in patch description

[ Impact: cleanup ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Acked-by: Stephen Rothwell <sfr@canb.auug.org.au>
Tested-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Ackec-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Cc: Borislav Petkov <petkovbb@googlemail.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-05-11 09:50:53 +02:00
Tejun Heo
a7f5579234 block: kill blk_start_queueing()
blk_start_queueing() is identical to __blk_run_queue() except that it
doesn't check for recursion.  None of the current users depends on
blk_start_queueing() running request_fn directly.  Replace usages of
blk_start_queueing() with [__]blk_run_queue() and kill it.

[ Impact: removal of mostly duplicate interface function ]

Signed-off-by: Tejun Heo <tj@kernel.org>
2009-04-28 07:37:33 +02:00
Jens Axboe
f2d1f0ae78 cfq-iosched: cache prio_tree root in cfqq->p_root
Currently we look it up from ->ioprio, but ->ioprio can change if
either the process gets its IO priority changed explicitly, or if
cfq decides to temporarily boost it. So if we are unlucky, we can
end up attempting to remove a node from a different rbtree root than
where it was added.

Fix this by using ->org_ioprio as the prio_tree index, since that
will only change for explicit IO priority settings (not for a boost).
Additionally cache the rbtree root inside the cfqq, then we don't have
to add code to reinsert the cfqq in the prio_tree if IO priority changes.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-04-24 08:54:22 +02:00
Jens Axboe
3ac6c9f8a6 cfq-iosched: fix bug with aliased request and cooperation detection
cfq_prio_tree_lookup() should return the direct match, yet it always
returns zero. Fix that.

cfq_prio_tree_add() assumes that we don't get a direct match, while
it is very possible that we do. Using O_DIRECT, you can have different
cfqq with matching requests, since you don't have the page cache
to serialize things for you. Fix this bug by only adding the cfqq if
there isn't an existing match.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-04-24 08:54:22 +02:00
Jens Axboe
26a2ac009c cfq-iosched: clear ->prio_trees[] on cfqd alloc
Not strictly needed, but we should make it clear that we init the
rbtree roots here.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-04-24 08:54:22 +02:00
Jeff Moyer
04dc6e71a2 cfq-iosched: use the default seek distance when there aren't enough seek samples
If the cfq io context doesn't have enough samples yet to provide a mean
seek distance, then use the default threshold we have for seeky IO instead
of defaulting to 0.

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-04-22 08:35:11 +02:00
Jeff Moyer
4d00aa47e2 cfq-iosched: make seek_mean converge more quickly
Right now, depending on the first sector to which a process issues I/O,
the seek time may start out way out of whack. So make sure we start
with 0 sectors in seek, instead of the offset of the first request
issued.

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-04-22 08:35:11 +02:00
Jens Axboe
a36e71f996 cfq-iosched: add close cooperator code
If we have processes that are working in close proximity to each
other on disk, we don't want to idle wait. Instead allow the close
process to issue a request, getting better aggregate bandwidth.
The anticipatory scheduler has similar checks, noop and deadline do
not need it since they don't care about process <-> io mappings.

The code for CFQ is a little more involved though, since we split
request queues into per-process contexts.

This fixes a performance problem with eg dump(8), since it uses
several processes in some silly attempt to speed IO up. Even if
dump(8) isn't really a valid case (it should be fixed by using
CLONE_IO), there are other cases where we see close processes
and where idling ends up hurting performance.

Credit goes to Jeff Moyer <jmoyer@redhat.com> for writing the
initial implementation.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-04-15 12:15:11 +02:00
Jens Axboe
9481ffdc61 cfq-iosched: log responsible 'cfqq' in idle timer arm
Makes it easier to read the traces.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-04-15 12:14:13 +02:00
Jens Axboe
2d87072296 cfq-iosched: tweak kick logic a bit more
We only kick the dispatch for an idling queue, if we think it's a
(somewhat) fully merged request. Also allow a kick if we have other
busy queues in the system, since we don't want to risk waiting for
a potential merge in that case. It's better to get some work done and
proceed.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-04-15 12:12:46 +02:00
Jens Axboe
40bb54d197 cfq-iosched: no need to save interrupts in cfq_kick_queue()
It's called from the workqueue handlers from process context, so
we always have irqs enabled when entered.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-04-15 12:11:10 +02:00
Jens Axboe
d6ceb25e8d cfq-iosched: don't delay queue kick for a merged request
"Zhang, Yanmin" <yanmin_zhang@linux.intel.com> reports that commit
b029195dda introduced a regression
of about 50% with sequential threaded read workloads. The test
case is:

tiotest -k0 -k1 -k3 -f 80 -t 32

which starts 32 threads each reading a 80MB file. Twiddle the kick
queue logic so that we do start IO immediately, if it appears to be
a fully merged request. We can't really detect that, so just check
if the request is bigger than a page or not. The assumption is that
since single bio issues will first queue a single request with just
one page attached and then later do merges on that, if we already
have more than a page worth of data in the request, then the request
is most likely good to go.

Verified that this doesn't cause a regression with the test case that
commit b029195dda was fixing. It does not,
we still see maximum sized requests for the queue-then-merge cases.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-04-15 08:28:12 +02:00
Jens Axboe
ff6657c6c8 cfq-iosched: get rid of private SYNC/ASYNC defines
We can just use the block layer BLK_RW_SYNC/ASYNC defines now.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-04-15 08:28:10 +02:00
Jens Axboe
b0b78f81a5 cfq-iosched: use rw_is_sync() to see if rw flags are sync or not
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-04-15 08:28:10 +02:00
Jens Axboe
b029195dda cfq-iosched: don't let idling interfere with plugging
When CFQ is waiting for a new request from a process, currently it'll
immediately restart queuing when it sees such a request. This doesn't
work very well with streamed IO, since we then end up splitting IO
that would otherwise have been merged nicely. For a simple dd test,
this causes 10x as many requests to be issued as we should have.
Normally this goes unnoticed due to the low overhead of requests
at the device side, but some hardware is very sensitive to request
sizes and there it can cause big slow downs.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-04-07 11:38:31 +02:00
Jens Axboe
75e50984f0 cfq-iosched: kill two unused cfqq flags
We only manipulate the must_dispatch and queue_new flags, they are not
tested anymore. So get rid of them.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-04-07 08:56:14 +02:00
Jens Axboe
2f5cb7381b cfq-iosched: change dispatch logic to deal with single requests at the time
The IO scheduler core calls into the IO scheduler dispatch_request hook
to move requests from the IO scheduler and into the driver dispatch
list. It only does so when the dispatch list is empty. CFQ moves several
requests to the dispatch list, which can cause higher latencies if we
suddenly have to switch to some important sync IO. Change the logic to
move one request at the time instead.

This should almost be functionally equivalent to what we did before,
except that we now honor 'quantum' as the maximum queue depth at the
device side from any single cfqq. If there's just a single active
cfqq, we allow up to 4 times the normal quantum.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-04-07 08:51:19 +02:00
Jens Axboe
aeb6fafb8f block: Add flag for telling the IO schedulers NOT to anticipate more IO
By default, CFQ will anticipate more IO from a given io context if the
previously completed IO was sync. This used to be fine, since the only
sync IO was reads and O_DIRECT writes. But with more "normal" sync writes
being used now, we don't want to anticipate for those.

Add a bio/request flag that informs the IO scheduler that this is a sync
request that we should not idle for. Introduce WRITE_ODIRECT specifically
for O_DIRECT writes, and make sure that the other sync writes set this
flag.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-04-06 08:04:54 -07:00
Divyesh Shah
3a9a3f6cc5 cfq-iosched: Allow RT requests to pre-empt ongoing BE timeslice
This patch adds the ability to pre-empt an ongoing BE timeslice when a RT
request is waiting for the current timeslice to complete. This reduces the
wait time to disk for RT requests from an upper bound of 4 (current value
of cfq_quantum) to 1 disk request.

Applied Jens' suggeested changes to avoid the rb lookup and use !cfq_class_rt()
and retested.

Latency(secs) for the RT task when doing sequential reads from 10G file.
                       | only RT | RT + BE | RT + BE + this patch
small (512 byte) reads | 143     | 163     | 145
large (1Mb) reads      | 142     | 158     | 146

Signed-off-by: Divyesh Shah <dpshah@google.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-01-30 12:47:33 +01:00
Jens Axboe
62c1fe9d9f cfq-iosched: fix race between exiting queue and exiting task
Original patch from Nikanth Karthikesan <knikanth@suse.de>

When a queue exits the queue lock is taken and cfq_exit_queue() would free all
the cic's associated with the queue.

But when a task exits, cfq_exit_io_context() gets cic one by one and then
locks the associated queue to call __cfq_exit_single_io_context. It looks like
between getting a cic from the ioc and locking the queue, the queue might have
exited on another cpu.

Fix this by rechecking the cfq_io_context queue key inside the queue lock
again, and not calling into __cfq_exit_single_io_context() if somebody
beat us to it.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-12-29 08:29:52 +01:00
Jens Axboe
30e0dc28bf cfq-iosched: remove limit of dispatch depth of max 4 times quantum
This basically limits the hardware queue depth to 4*quantum at any
point in time, which is 16 with the default settings. As CFQ uses
other means to shrink the hardware queue when necessary in the first
place, there's really no need for this extra heuristic. Additionally,
it ends up hurting performance in some cases.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-12-29 08:29:51 +01:00
Jens Axboe
b374d18a4b block: get rid of elevator_t typedef
Just use struct elevator_queue everywhere instead.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-12-29 08:29:50 +01:00
Cheng Renquan
64d01dc9e1 block: use cancel_work_sync() instead of kblockd_flush_work()
After many improvements on kblockd_flush_work, it is now identical to
cancel_work_sync, so a direct call to cancel_work_sync is suggested.

The only difference is that cancel_work_sync is a GPL symbol,
so no non-GPL modules anymore.

Signed-off-by: Cheng Renquan <crquan@gmail.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-12-29 08:28:44 +01:00
Jens Axboe
f7d7b7a7a3 block: as/cfq ssd idle check update
We really need to know about the hardware tagging support as well,
since if the SSD does not do tagging then we still want to idle.
Otherwise have the same dependent sync IO vs flooding async IO
problem as on rotational media.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-10-09 08:56:19 +02:00
Jens Axboe
a68bbddba4 block: add queue flag for SSD/non-rotational devices
We don't want to idle in AS/CFQ if the device doesn't have a seek
penalty. So add a QUEUE_FLAG_NONROT to indicate a non-rotational
device, low level drivers should set this flag upon discovery of
an SSD or similar device type.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-10-09 08:56:19 +02:00
Aaron Carroll
45333d5a31 cfq-iosched: fix queue depth detection
CFQ's detection of queueing devices assumes a non-queuing device and detects
if the queue depth reaches a certain threshold.  Under some workloads (e.g.
synchronous reads), CFQ effectively forces a unit queue depth, thus defeating
the detection logic.  This leads to poor performance on queuing hardware,
since the idle window remains enabled.

This patch inverts the sense of the logic: assume a queuing-capable device,
and detect if the depth does not exceed the threshold.

Signed-off-by: Aaron Carroll <aaronc@gelato.unsw.edu.au>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-10-09 08:56:09 +02:00
Jens Axboe
18887ad910 block: make kblockd_schedule_work() take the queue as parameter
Preparatory patch for checking queuing affinity.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-10-09 08:56:09 +02:00
Jens Axboe
c265a7f417 cfq-iosched: get rid of enable_idle being unused warning
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-07-03 13:21:14 +02:00
Jens Axboe
7b679138b3 cfq-iosched: add message logging through blktrace
Now that blktrace has the ability to carry arbitrary messages in
its stream, use that for some CFQ logging.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-07-03 13:21:12 +02:00
Jens Axboe
9a11b4ed0e cfq-iosched: properly protect ioc_gone and ioc count
If we have multiple tasks freeing cfq_io_contexts when cfq-iosched
is being unloaded, we could complete() ioc_gone twice. Fix that by
protecting ioc_gone complete() and clearing with a spinlock for
just that purpose. Doesn't matter from a performance perspective,
since it'll only enter that path when ioc_gone != NULL (when cfq-iosched
is being rmmod'ed).

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-07-03 13:21:12 +02:00
Jens Axboe
d6de8be711 cfq-iosched: fix RCU problem in cfq_cic_lookup()
cfq_cic_lookup() needs to properly protect ioc->ioc_data before
dereferencing it and also exclude updaters of ioc->ioc_data as well.

Also add a number of comments documenting why the existing RCU usage
is OK.

Thanks a lot to "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> for
review and comments!

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-05-28 14:49:28 +02:00
Richard Kennedy
be754d2c21 block: reorder cfq_queue to save space on 64bit builds
saves 8 bytes of padding & increases objects/slab from 30 to 32 on my
AMD64 config

Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-05-28 14:49:27 +02:00
Jens Axboe
6d63c27557 cfq-iosched: make io priorities inherit CPU scheduling class as well as nice
We currently set all processes to the best-effort scheduling class,
regardless of what CPU scheduling class they belong to. Improve that
so that we correctly track idle and rt scheduling classes as well.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-05-07 09:51:23 +02:00
Jens Axboe
07416d29bc cfq-iosched: fix RCU race in the cfq io_context destructor handling
put_io_context() drops the RCU read lock before calling into cfq_dtor(),
however we need to hold off freeing there before grabbing and
dereferencing the first object on the list.

So extend the rcu_read_lock() scope to cover the calling of cfq_dtor(),
and optimize cfq_free_io_context() to use a new variant for
call_for_each_cic() that assumes the RCU read lock is already held.

Hit in the wild by Alexey Dobriyan <adobriyan@gmail.com>

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-05-07 09:28:57 +02:00
Fabio Checconi
4faa3c8150 cfq-iosched: do not leak ioc_data across iosched switches
When switching scheduler from cfq, cfq_exit_queue() does not clear
ioc->ioc_data, leaving a dangling pointer that can deceive the following
lookups when the iosched is switched back to cfq.  The pattern that can
trigger that is the following:

    - elevator switch from cfq to something else;
    - module unloading, with elv_unregister() that calls cfq_free_io_context()
      on ioc freeing the cic (via the .trim op);
    - module gets reloaded and the elevator switches back to cfq;
    - reallocation of a cic at the same address as before (with a valid key).

To fix it just assign NULL to ioc_data in __cfq_exit_single_io_context(),
that is called from the regular exit path and from the elevator switching
code.  The only path that frees a cic and is not covered is the error handling
one, but cic's freed in this way are never cached in ioc_data.

Signed-off-by: Fabio Checconi <fabio@gandalf.sssup.it>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-04-10 08:28:01 +02:00
Fabio Checconi
34e6bbf23c cfq-iosched: fix rcu freeing of cfq io contexts
SLAB_DESTROY_BY_RCU is not a direct substitute for normal call_rcu()
freeing, since it'll page freeing but NOT object freeing. So change
cfq to do the freeing on its own.

Signed-off-by: Fabio Checconi <fabio@gandalf.sssup.it>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-04-02 15:42:20 +02:00
Jens Axboe
ffc4e75957 cfq-iosched: add hlist for browsing parallel to the radix tree
It's cumbersome to browse a radix tree from start to finish, especially
since we modify keys when a process exits. So add a hlist for the single
purpose of browsing over all known cfq_io_contexts, used for exit,
io prio change, etc.

This fixes http://bugzilla.kernel.org/show_bug.cgi?id=9948

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-02-19 10:04:00 +01:00
Jens Axboe
fe094d98e7 cfq-iosched: make checkpatch compliant
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-02-01 09:26:33 +01:00
Jens Axboe
febffd6181 cfq-iosched: kill some big inlines
Use of inlines were a bit over the top, trim them down a bit.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-01-28 13:19:43 +01:00
Jens Axboe
0871714e08 cfq-iosched: relax IOPRIO_CLASS_IDLE restrictions
Currently you must be root to set idle io prio class on a process. This
is due to the fact that the idle class is implemented as a true idle
class, meaning that it will not make progress if someone else is
requesting disk access. Unfortunately this means that it opens DOS
opportunities by locking down file system resources, hence it is root
only at the moment.

This patch relaxes the idle class a little, by removing the truly idle
part (which entals a grace period with associated timer). The
modifications make the idle class as close to zero impact as can be done
while still guarenteeing progress. This means we can relax the root only
criteria as well.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-01-28 11:38:15 +01:00
Jens Axboe
4ac845a2e9 block: cfq: make the io contect sharing lockless
The io context sharing introduced a per-ioc spinlock, that would protect
the cfq io context lookup. That is a regression from the original, since
we never needed any locking there because the ioc/cic were process private.

The cic lookup is changed from an rbtree construct to a radix tree, which
we can then use RCU to make the reader side lockless. That is the performance
critical path, modifying the radix tree is only done on process creation
(when that process first does IO, actually) and on process exit (if that
process has done IO).

As it so happens, radix trees are also much faster for this type of
lookup where the key is a pointer. It's a very sparse tree.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-01-28 10:50:33 +01:00
Nikanth Karthikesan
66dac98ed0 io_context sharing - cfq changes
changes in the cfq for io_context sharing

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-01-28 10:50:32 +01:00
Jens Axboe
fd0928df98 ioprio: move io priority from task_struct to io_context
This is where it belongs and then it doesn't take up space for a
process that doesn't do IO.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-01-28 10:50:29 +01:00
Adrian Bunk
2fdd82bd88 block: let elv_register() return void
elv_register() always returns 0, and there isn't anything it does where
it should return an error (the only error condition is so grave that
it's handled with a BUG_ON).

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-12-18 08:29:28 +01:00
Oleg Nesterov
0e7be9edb9 cfq_idle_class_timer: add paranoid checks for jiffies overflow
In theory, if the queue was idle long enough, cfq_idle_class_timer may have
a false (and very long) timeout because jiffies can wrap into the past wrt
->last_end_request.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-11-07 13:51:35 +01:00
Oleg Nesterov
b70c864d3c cfq: fix IOPRIO_CLASS_IDLE delays
After the fresh boot:

	ionice -c3 -p $$
	echo cfq >> /sys/block/XXX/queue/scheduler
	dd if=/dev/XXX of=/dev/null bs=512 count=1

Now dd hangs in D state and the queue is completely stalled for approximately
INITIAL_JIFFIES + CFQ_IDLE_GRACE jiffies. This is because cfq_init_queue()
forgets to initialize cfq_data->last_end_request.

(I guess this patch is not complete, overflow is still possible)

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-11-07 09:46:13 +01:00
Oleg Nesterov
2389d1ef17 cfq: fix IOPRIO_CLASS_IDLE accounting
Spotted by Nick <gentuu@gmail.com>, hopefully can explain the second trace in
http://bugzilla.kernel.org/show_bug.cgi?id=9180.

If ->async_idle_cfqq != NULL cfq_put_async_queues() puts it IOPRIO_BE_NR times
in a loop. Fix this.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-11-07 09:45:00 +01:00
Oleg Nesterov
0a0836a09c cfq_get_queue: fix possible NULL pointer access
cfq_get_queue()->cfq_find_alloc_queue() can fail, check the returned value.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>

Note that this isn't a bug at the moment, since the regular IO path
does not call this path without __GFP_WAIT set. However, it could be a
future bug, so I've applied it.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-10-29 11:33:05 +01:00
Oleg Nesterov
4310864b9d cfq_exit_queue() should cancel cfq_data->unplug_work
Spotted by Nick <gentuu@gmail.com>, perhaps explains the first trace in
http://bugzilla.kernel.org/show_bug.cgi?id=9180.

cfq_exit_queue() should cancel cfqd->unplug_work before freeing cfqd.
blk_sync_queue() seems unneeded, removed.

Q: why cfq_exit_queue() calls cfq_shutdown_timer_wq() twice?

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-10-29 11:33:05 +01:00
Jens Axboe
165125e1e4 [BLOCK] Get rid of request_queue_t typedef
Some of the code has been gradually transitioned to using the proper
struct request_queue, but there's lots left. So do a full sweet of
the kernel and get rid of this typedef and replace its uses with
the proper type.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-24 09:28:11 +02:00
Alexey Dobriyan
8350163a90 cfq: Write-only stuff in CFQ data structures
There are some leftover bits from the task cooperator patch, that was
yanked out again. While it will get reintroduced, no point in having
this write-only stuff in the tree. So yank it.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-20 10:07:50 +02:00
Vasily Tarasov
c2dea2d1fd cfq: async queue allocation per priority
If we have two processes with different ioprio_class, but the same
ioprio_data, their async requests will fall into the same queue. I guess
such behavior is not expected, because it's not right to put real-time
requests and best-effort requests in the same queue.

The attached patch fixes the problem by introducing additional *cfqq
fields on cfqd, pointing to per-(class,priority) async queues.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-20 10:06:38 +02:00
Christoph Lameter
94f6030ca7 Slab allocators: Replace explicit zeroing with __GFP_ZERO
kmalloc_node() and kmem_cache_alloc_node() were not available in a zeroing
variant in the past.  But with __GFP_ZERO it is possible now to do zeroing
while allocating.

Use __GFP_ZERO to remove the explicit clearing of memory via memset whereever
we can.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-17 10:23:02 -07:00
Jens Axboe
15c31be4d5 cfq-iosched: fix async queue behaviour
With the cfq_queue hash removal, we inadvertently got rid of the
async queue sharing. This was not intentional, in fact CFQ purposely
shares the async queue per priority level to get good merging for
async writes.

So put some logic in cfq_get_queue() to track the shared queues.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-07-10 13:43:25 +02:00
Christoph Lameter
0a31bd5f2b KMEM_CACHE(): simplify slab cache creation
This patch provides a new macro

KMEM_CACHE(<struct>, <flags>)

to simplify slab creation. KMEM_CACHE creates a slab with the name of the
struct, with the size of the struct and with the alignment of the struct.
Additional slab flags may be specified if necessary.

Example

struct test_slab {
	int a,b,c;
	struct list_head;
} __cacheline_aligned_in_smp;

test_slab_cache = KMEM_CACHE(test_slab, SLAB_PANIC)

will create a new slab named "test_slab" of the size sizeof(struct
test_slab) and aligned to the alignment of test slab.  If it fails then we
panic.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-07 12:12:55 -07:00
Jens Axboe
597bc485d6 cfq-iosched: speedup cic rb lookup
We often lookup the same queue many times in succession, so cache
the last looked up queue to avoid browsing the rbtree.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-04-30 09:01:23 +02:00
Vasily Tarasov
91fac317a3 cfq-iosched: get rid of cfqq hash
cfq hash is no more necessary.  We always can get cfqq from io context.
cfq_get_io_context_noalloc() function is introduced, because we don't
want to allocate cic on merging and checking may_queue.  In order to
identify sync queue we've used hash key = CFQ_KEY_ASYNC. Since hash is
eliminated we need to use other criterion: sync flag for queue is added.
In all places where we dig in rb_tree we're in current context, so no
additional locking is required.

Advantages of this patch: no additional memory for hash, no seeking in
hash, code is cleaner. But it is necessary now to seek cic in per-ioc
rbtree, but it is faster:
- most processes work only with few devices
- most systems have only few block devices
- it is a rb-tree

Signed-off-by: Vasily Tarasov <vtaras@openvz.org>

Changes by me:

- Merge into CFQ devel branch
- Get rid of cfq_get_io_context_noalloc()
- Fix various bugs with dereferencing cic->cfqq[] with offset other
  than 0 or 1.
- Fix bug in cfqq setup, is_sync condition was reversed.
- Fix bug where only bio_sync() is used, we need to check for a READ too

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-04-30 09:01:23 +02:00
Jens Axboe
cc19747977 cfq-iosched: tighten queue request overlap condition
For tagged devices, allow overlap of requests if the idle window
isn't enabled on the current active queue.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-04-30 09:01:23 +02:00
Jens Axboe
3ed9a2965c cfq-iosched: improve sync vs async workloads
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-04-30 09:01:23 +02:00
Jens Axboe
1be92f2fc7 cfq-iosched: never allow an async queue idling
We don't enable it by default, don't let it get enabled during
runtime.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-04-30 09:01:22 +02:00
Jens Axboe
20e493a8d0 cfq-iosched: get rid of ->dispatch_slice
We can track it fairly accurately locally, let the slice handling
take care of the rest.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-04-30 09:01:22 +02:00
Jens Axboe
6084cdda0e cfq-iosched: don't pass unused preemption variable around
We don't use it anymore in the slice expiry handling.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-04-30 09:01:22 +02:00