Re: [ 11/37] sched/nohz: Rewrite and fix load-avg computation -- again

[Jonathan Nieder <jrnieder@gmail.com>]

Hi,

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@linux-foundation.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>

(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(-)

Thanks,
Jonathan