Message-ID: <510493E4.8060602@intel.com>
Date:	Sun, 27 Jan 2013 10:41:40 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	Borislav Petkov <bp@...en8.de>, torvalds@...ux-foundation.org,
	mingo@...hat.com, peterz@...radead.org, tglx@...utronix.de,
	akpm@...ux-foundation.org, arjan@...ux.intel.com, pjt@...gle.com,
	namhyung@...nel.org, efault@....de, vincent.guittot@...aro.org,
	gregkh@...uxfoundation.org, preeti@...ux.vnet.ibm.com,
	viresh.kumar@...aro.org, linux-kernel@...r.kernel.org
Subject: Re: [patch v4 0/18] sched: simplified fork, release load avg and
 power awareness scheduling

On 01/24/2013 11:07 PM, Alex Shi wrote:
> On 01/24/2013 05:44 PM, Borislav Petkov wrote:
>> On Thu, Jan 24, 2013 at 11:06:42AM +0800, Alex Shi wrote:
>>> Since the runnable info needs 345ms to accumulate, balancing
>>> doesn't do well for many tasks burst waking. After talking with Mike
>>> Galbraith, we are agree to just use runnable avg in power friendly 
>>> scheduling and keep current instant load in performance scheduling for 
>>> low latency.
>>>
>>> So the biggest change in this version is removing runnable load avg in
>>> balance and just using runnable data in power balance.
>>>
>>> The patchset bases on Linus' tree, includes 3 parts,
>>> ** 1, bug fix and fork/wake balancing clean up. patch 1~5,
>>> ----------------------
>>> the first patch remove one domain level. patch 2~5 simplified fork/wake
>>> balancing, it can increase 10+% hackbench performance on our 4 sockets
>>> SNB EP machine.
>>
>> Ok, I see some benchmarking results here and there in the commit
>> messages but since this is touching the scheduler, you probably would
>> need to make sure it doesn't introduce performance regressions vs
>> mainline with a comprehensive set of benchmarks.
>>
> 
> Thanks a lot for your comments, Borislav! :)
> 
> For this patchset, the code will just check current policy, if it is
> performance, the code patch will back to original performance code at
> once. So there should no performance change on performance policy.
> 
> I once tested the balance policy performance with benchmark
> kbuild/hackbench/aim9/dbench/tbench on version 2, only hackbench has a
> bit drop ~3%. others have no clear change.
> 
>> And, AFAICR, mainline does by default the 'performance' scheme by
>> spreading out tasks to idle cores, so have you tried comparing vanilla
>> mainline to your patchset in the 'performance' setting so that you can
>> make sure there are no problems there? And not only hackbench or a
>> microbenchmark but aim9 (I saw that in a commit message somewhere) and
>> whatever else multithreaded benchmark you can get your hands on.
>>
>> Also, you might want to run it on other machines too, not only SNB :-)
> 
> Anyway I will redo the performance testing on this version again on all
> machine. but doesn't expect something change. :)

Just rerun some benchmarks: kbuild, specjbb2005, oltp, tbench, aim9,
hackbench, fileio-cfq of sysbench, dbench, aiostress, multhreads
loopback netperf. on my core2, nhm, wsm, snb, platforms. no clear
performance change found.

I also tested balance policy/powersaving policy with above benchmark,
found, the specjbb2005 drop much 30~50% on both of policy whenever with
openjdk or jrockit. and hackbench drops a lots with powersaving policy
on snb 4 sockets platforms. others has no clear change.

> 
>> And what about ARM, maybe someone there can run your patchset too?
>>
>> So, it would be cool to see comprehensive results from all those runs
>> and see what the numbers say.
>>
>> Thanks.
>>
> 
> 


-- 
Thanks
    Alex
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