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SubjectRE: scale sysctl_sched_shares_ratelimit with nr_cpus
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>>-----Original Message-----
>>From: Ingo Molnar [mailto:mingo@elte.hu]
>>Sent: Monday, August 18, 2008 3:02 PM
>>To: Zhang, Yanmin
>>Cc: a.p.zijlstra@chello.nl; Linux Kernel Mailing List
>>Subject: Re: scale sysctl_sched_shares_ratelimit with nr_cpus
>>
>>
>>* Zhang, Yanmin <yanmin.zhang@intel.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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