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[PATCH] rcu: simplify/improve batch tuning

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Kill a hard-to-calculate 'rsinterval' boot parameter and per-cpu
rcu_data.last_rs_qlen.  Instead, it adds adds a flag rcu_ctrlblk.signaled,
which records the fact that one of CPUs has sent a resched IPI since the
last rcu_start_batch().

Roughly speaking, we need two rcu_start_batch()s in order to move callbacks
from ->nxtlist to ->donelist.  This means that when ->qlen exceeds qhimark
and continues to grow, we should send a resched IPI, and then do it again
after we gone through a quiescent state.

On the other hand, if it was already sent, we don't need to do it again
when another CPU detects overflow of the queue.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Oleg Nesterov
2006-10-04 02:17:17 -07:00
committed by Linus Torvalds
parent 4b6c2cca6e
commit 20e9751bd9
3 changed files with 5 additions and 15 deletions
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4
Documentation/kernel-parameters.txt
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@ -1357,10 +1357,6 @@ and is between 256 and 4096 characters. It is defined in the file
rcu.qlowmark= [KNL,BOOT] Set threshold of queued
RCU callbacks below which batch limiting is re-enabled.
rcu.rsinterval= [KNL,BOOT,SMP] Set the number of additional
RCU callbacks to queued before forcing reschedule
on all cpus.
rdinit= [KNL]
Format: <full_path>
Run specified binary instead of /init from the ramdisk,