sched/nohz: Rewrite and fix load-avg computation -- again

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Thanks to Charles Wang for spotting the defects in the current code:

 - If we go idle during the sample window -- after sampling, we get a
   negative bias because we can negate our own sample.

 - If we wake up during the sample window we get a positive bias
   because we push the sample to a known active period.

So rewrite the entire nohz load-avg muck once again, now adding
copious documentation to the code.

Reported-and-tested-by: Doug Smythies <dsmythies@telus.net>
Reported-and-tested-by: Charles Wang <muming.wq@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: stable@kernel.org
Link: http://lkml.kernel.org/r/1340373782.18025.74.camel@twins
[ minor edits ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

...

This commit is contained in:

Peter Zijlstra 2012-06-22 15:52:09 +02:00 • committed by Ingo Molnar

parent 164c33c6ad

commit 5167e8d541

5 changed files with 213 additions and 75 deletions

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8

include/linux/sched.h

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277

kernel/sched/core.c

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1

kernel/sched/idle_task.c

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2

kernel/sched/sched.h

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2

kernel/time/tick-sched.c

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