linux-kernel - Re: scale sysctl_sched_shares_ratelimit with nr

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Date:	Mon, 18 Aug 2008 10:42:01 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	"Zhang, Yanmin" <yanmin.zhang@...el.com>
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


* Zhang, Yanmin <yanmin.zhang@...el.com> wrote:

> >>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.

hm, does this mean there's too much idle time during the testrun, 
because we dont load-balance agressively enough?

	Ingo
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