lk/linux-kernel-test
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

memcg: add per cgroup writeback pages accounting

Browse Source 
Add memcg routines to count writeback pages, later dirty pages will also
be accounted.

After Kame's commit 89c06bd52f ("memcg: use new logic for page stat
accounting"), we can use 'struct page' flag to test page state instead
of per page_cgroup flag.  But memcg has a feature to move a page from a
cgroup to another one and may have race between "move" and "page stat
accounting".  So in order to avoid the race we have designed a new lock:

         mem_cgroup_begin_update_page_stat()
         modify page information        -->(a)
         mem_cgroup_update_page_stat()  -->(b)
         mem_cgroup_end_update_page_stat()

It requires both (a) and (b)(writeback pages accounting) to be pretected
in mem_cgroup_{begin/end}_update_page_stat().  It's full no-op for
!CONFIG_MEMCG, almost no-op if memcg is disabled (but compiled in), rcu
read lock in the most cases (no task is moving), and spin_lock_irqsave
on top in the slow path.

There're two writeback interfaces to modify: test_{clear/set}_page_writeback().
And the lock order is:
	--> memcg->move_lock
	  --> mapping->tree_lock

Signed-off-by: Sha Zhengju <handai.szj@taobao.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Greg Thelen <gthelen@google.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Sha Zhengju
2013-09-12 15:13:53 -07:00
committed by Linus Torvalds
parent 658b72c5a7
commit 3ea67d06e4
3 changed files with 39 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

15
mm/page-writeback.c
View File

@@ -2143,11 +2143,17 @@ EXPORT_SYMBOL(account_page_dirtied);
/*
* Helper function for set_page_writeback family.
*
* The caller must hold mem_cgroup_begin/end_update_page_stat() lock
* while calling this function.
* See test_set_page_writeback for example.
*
* NOTE: Unlike account_page_dirtied this does not rely on being atomic
* wrt interrupts.
*/
void account_page_writeback(struct page *page)
{
mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_WRITEBACK);
inc_zone_page_state(page, NR_WRITEBACK);
}
EXPORT_SYMBOL(account_page_writeback);
@@ -2364,7 +2370,10 @@ int test_clear_page_writeback(struct page *page)
{
struct address_space *mapping = page_mapping(page);
int ret;
bool locked;
unsigned long memcg_flags;
mem_cgroup_begin_update_page_stat(page, &locked, &memcg_flags);
if (mapping) {
struct backing_dev_info *bdi = mapping->backing_dev_info;
unsigned long flags;
@@ -2385,9 +2394,11 @@ int test_clear_page_writeback(struct page *page)
ret = TestClearPageWriteback(page);
}
if (ret) {
mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_WRITEBACK);
dec_zone_page_state(page, NR_WRITEBACK);
inc_zone_page_state(page, NR_WRITTEN);
}
mem_cgroup_end_update_page_stat(page, &locked, &memcg_flags);
return ret;
}
@@ -2395,7 +2406,10 @@ int test_set_page_writeback(struct page *page)
{
struct address_space *mapping = page_mapping(page);
int ret;
bool locked;
unsigned long memcg_flags;
mem_cgroup_begin_update_page_stat(page, &locked, &memcg_flags);
if (mapping) {
struct backing_dev_info *bdi = mapping->backing_dev_info;
unsigned long flags;
@@ -2422,6 +2436,7 @@ int test_set_page_writeback(struct page *page)
}
if (!ret)
account_page_writeback(page);
mem_cgroup_end_update_page_stat(page, &locked, &memcg_flags);
return ret;
}