tree 30dbb20798fde88a09680e9d82bd32ad8c343692
parent d6d5cfaf4551aa7713ca6ab73bb77e832602204b
author Nick Piggin <nickpiggin@yahoo.com.au> 1126337178 -0700
committer Linus Torvalds <torvalds@g5.osdl.org> 1126371983 -0700

[PATCH] sched: less locking

During periodic load balancing, don't hold this runqueue's lock while
scanning remote runqueues, which can take a non trivial amount of time
especially on very large systems.

Holding the runqueue lock will only help to stabilise ->nr_running, however
this doesn't do much to help because tasks being woken will simply get held
up on the runqueue lock, so ->nr_running would not provide a really
accurate picture of runqueue load in that case anyway.

What's more, ->nr_running (and possibly the cpu_load averages) of remote
runqueues won't be stable anyway, so load balancing is always an inexact
operation.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>