linux-kernel - RE: scale sysctl_sched_shares_ratelimit with nr

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Date:	Mon, 18 Aug 2008 16:26:09 +0800
From:	"Zhang, Yanmin" <yanmin.zhang@...el.com>
To:	"Ingo Molnar" <mingo@...e.hu>
Cc:	<a.p.zijlstra@...llo.nl>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: RE: scale sysctl_sched_shares_ratelimit with nr_cpus



>>-----Original Message-----
>>From: Ingo Molnar [mailto:mingo@...e.hu]
>>Sent: Monday, August 18, 2008 3:02 PM
>>To: Zhang, Yanmin
>>Cc: a.p.zijlstra@...llo.nl; Linux Kernel Mailing List
>>Subject: Re: scale sysctl_sched_shares_ratelimit with nr_cpus
>>
>>
>>* Zhang, Yanmin <yanmin.zhang@...el.com> wrote:
>>
>>> >>cool. It's already upstream (post-rc3 commit):
>>> [YM] But comparing with 2.6.26, volanoMark result still has about
60%
>>> regression.
>>
>>Does a scheduler trace show anything about why that drop happens? Do
>>something like this to trace the scheduler:
>>
>>assuming debugfs is mounted under /debug and CONFIG_SCHED_TRACER=y:
>>
>>  echo 1 > /debug/tracing/tracing_cpumask
>>  echo sched_switch > /debug/tracing/available_tracers
>>  cat /debug/tracing/trace_pipe > trace.txt
[YM] Thanks for your good pointer. I collected the data and didn't find
anything abnormal except the pid about waker.

    Receiver-197-13665 [00]  1369.966423:  13665:120:R   + 13607:120:S
    Receiver-197-13665 [00]  1369.966440:  13665:120:R   + 13611:120:S
    Receiver-197-13665 [00]  1369.966458:  13665:120:R   + 13615:120:S
    Receiver-197-13665 [00]  1369.966463:  13665:120:R   + 13619:120:S
    Receiver-197-13665 [00]  1369.966466:  13665:120:R   + 13623:120:S
    Receiver-197-13665 [00]  1369.966469:  13665:120:R   + 13627:120:S
    Receiver-197-13665 [00]  1369.966475:  13665:120:R   + 13631:120:S
    Receiver-197-13665 [00]  1369.966480:  13665:120:R   + 13635:120:S
    Receiver-197-13665 [00]  1369.966485:  13665:120:R   + 13639:120:S
    Receiver-197-13665 [00]  1369.966495:  13665:120:R   + 13643:120:S
    Receiver-197-13665 [00]  1369.966507:  13871:120:R   + 13647:120:S
Above waker pid is 13871 while the current pid is 13665. I found lots of
such mismatch data.

    Receiver-197-13665 [00]  1369.966513:  13465:120:R   + 13651:120:S
    Receiver-197-13665 [00]  1369.966516:  13665:120:R   + 13655:120:S
    Receiver-197-13665 [00]  1369.966521:  13665:120:R   + 13659:120:S
    Receiver-197-13665 [00]  1369.966530:  13665:120:R   + 13667:120:S
    Receiver-197-13665 [00]  1369.966544:  13883:120:R   + 13663:120:S
    Receiver-197-13665 [00]  1369.966549:  13665:120:R ==> 13667:120:R
      Sender-140-13667 [00]  1369.966573:  13351:120:R   + 13668:120:S
      Sender-140-13667 [00]  1369.966578:  13667:120:R ==> 13659:120:R


BTW, I analyzed schedstat data and found wake_affine and
load_balance_newidle
seem abnormal. 2.6.27-rc has more task pulls.
I set CONFIG_GROUP_SCHED=n with above testing.

>>
>>( regarding tracing_cpumask: trace only 1 CPU to make sure volanomark
is
>>  not disturbed too much by many-CPUs tracing. )
>>
>>	Ingo
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