Re: [ 11/37] sched/nohz: Rewrite and fix load-avg computation --again
From: Jonathan Nieder
Date: Tue Jul 17 2012 - 20:16:19 EST
Greg Kroah-Hartman wrote:
> commit 5167e8d5417bf5c322a703d2927daec727ea40dd upstream.
> 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.
I'm thrilled to see this regression fix for stable@, but are we really
really sure that it won't cause new regressions?
Words like "rewrite" set off alarm bells. As do missing acks:
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
(though I guess there's an implied ack from Linus, given that it was
pulled). And big diffstats:
> include/linux/sched.h | 8 +
> kernel/sched/core.c | 275 ++++++++++++++++++++++++++++++++++-------------
> kernel/sched/idle_task.c | 1
> kernel/sched/sched.h | 2
> kernel/time/tick-sched.c | 2
> 5 files changed, 213 insertions(+), 75 deletions(-)
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