linux-kernel - Re: [PATCH] sched: wakeup buddy

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Date:	Tue, 12 Mar 2013 17:41:42 +0800
From:	Michael Wang <wangyun@...ux.vnet.ibm.com>
To:	Ingo Molnar <mingo@...nel.org>
CC:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	LKML <linux-kernel@...r.kernel.org>,
	Mike Galbraith <efault@....de>,
	Namhyung Kim <namhyung@...nel.org>,
	Alex Shi <alex.shi@...el.com>, Paul Turner <pjt@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Nikunj A. Dadhania" <nikunj@...ux.vnet.ibm.com>,
	Ram Pai <linuxram@...ibm.com>
Subject: Re: [PATCH] sched: wakeup buddy

On 03/12/2013 04:48 PM, Ingo Molnar wrote:
[snip]
>>>
>>> Instrumentation/stats/profiling will also double check the correctness of 
>>> this data: if developers/users start relying on the work metric as a 
>>> substitute benchmark number, then app writers will have an additional 
>>> incentive to make them correct.
>>
>> I see, I could not figure out how to wisely using the info currently, 
>> but I have the feeling that it will make scheduler very different ;-)
>>
>> May be we could implement the API and get those info ready firstly 
>> (along with the new sched-pipe which provide work tick info), then think 
>> about the way to use them in scheduler, is there any patches on the way?
> 
> Absolutely.
> 
> Beyond the new prctl no new API is needed: a perf soft event could be 
> added, and/or a tracepoint. Then perf stat and perf record could be used 
> with it. 'perf bench' could be extended to generate the work tick in its 
> 'perf bench sched ...' workloads - and for 'perf bench mem numa' as well.

Nice :)

> 
> vsyscall-accelerating it could be a separate, more complex step: it needs 
> a per thread writable vsyscall data area to make the overhead to 
> applications near zero. Performance critical apps won't call an extra 
> syscall.

If it's really bring benefit, I think they will consider about it,
whatever, that's the developer/users decision, what we need to do is
just make the stuff attractively.

Regards,
Michael Wang

> 
> Thanks,
> 
> 	Ingo
> 

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