linux-kernel - Re: Kernel 4.7rc3 - Performance drop 30-40% for SPECjbb2005 and SPECjvm2008 benchmarks against 4.6 kernel

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Message-ID: <CAE4VaGCYYddeoHwwUOQ_pHP8fXTzUN3z8Ec7acQoeAk1NRO4NA@mail.gmail.com>
Date:	Wed, 22 Jun 2016 14:46:21 +0200
From:	Jirka Hladky <jhladky@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Kamil Kolakowski <kkolakow@...hat.com>
Subject: Re: Kernel 4.7rc3 - Performance drop 30-40% for SPECjbb2005 and
 SPECjvm2008 benchmarks against 4.6 kernel

OK, I have reviewed my results once again:

This commit is fine:
64b7aad - Ingo Molnar, 7 weeks ago : Merge branch 'sched/urgent' into
sched/core, to pick up fixes before applying new changes

This version has already a problem:
2159197 - Peter Zijlstra, 8 weeks ago : sched/core: Enable increased
load resolution on 64-bit kernels

git bisect start
git bisect good 64b7aad
git bisect bad 2159197
Bisecting: 1 revision left to test after this (roughly 1 step)
[eb58075149b7f0300ff19142e6245fe75db2a081] sched/core: Introduce
'struct rq_flags'

I should have results pretty soon.

Jirka


On Wed, Jun 22, 2016 at 2:37 PM, Jirka Hladky <jhladky@...hat.com> wrote:
> Hi Peter,
>
> crap - I have done bisecting manually (not using git bisect) and I
> have probably done some mistake.
>
> Commits (git checkout <commit>) for which I got BAD results:
>
> 2159197d66770ec01f75c93fb11dc66df81fd45b
> 6ecdd74962f246dfe8750b7bea481a1c0816315d
>
> Commits (git checkout <commit>) for which I got GOOD results:
> 21e96f88776deead303ecd30a17d1d7c2a1776e3
> 64b7aad5798478ffff52e110878ccaae4c3aaa34
> e7904a28f5331c21d17af638cb477c83662e3cb6
>
> I will try to use git bisect now.
> 
> Jirka
>
> On Wed, Jun 22, 2016 at 1:12 PM, Peter Zijlstra <peterz@...radead.org> wrote:
>> On Wed, Jun 22, 2016 at 11:52:45AM +0200, Jirka Hladky wrote:
>>> Hi Peter,
>>>
>>> the performance regression has been caused by this commit
>>>
>>> =================================================
>>> commit 6ecdd74962f246dfe8750b7bea481a1c0816315d
>>> Author: Yuyang Du <yuyang.du@...el.com>
>>> Date:   Tue Apr 5 12:12:26 2016 +0800
>>>
>>>     sched/fair: Generalize the load/util averages resolution definition
>>> =================================================
>>>
>>> Could you please have a look?
>>
>> That patch looks like a NO-OP to me.
>>
>> In any case, the good news it that I can run the benchmark, the bad news
>> is that the patch you fingered doesn't appear to be it.
>>
>>
>> v4.60:
>> ./4.6.0/2016-Jun-22_11h11m07s.log:Score on xml.transform: 2007.18 ops/m
>> ./4.6.0/2016-Jun-22_11h11m07s.log:Score on xml.validation: 2999.44 ops/m
>>
>> tip/master:
>> ./4.7.0-rc4-00345-gf6e78bb/2016-Jun-22_11h30m27s.log:Score on xml.transform: 1283.14 ops/m
>> ./4.7.0-rc4-00345-gf6e78bb/2016-Jun-22_11h30m27s.log:Score on xml.validation: 2008.62 ops/m
>>
>> patch^1
>> ./4.6.0-rc5-00034-g2159197/2016-Jun-22_12h38m50s.log:Score on xml.transform: 1196.18 ops/m
>> ./4.6.0-rc5-00034-g2159197/2016-Jun-22_12h38m50s.log:Score on xml.validation: 2055.11 ops/m
>>
>> patch^1 + patch
>> ./4.6.0-rc5-00034-g2159197-dirty/2016-Jun-22_12h55m43s.log:Score on xml.transform: 1294.59 ops/m
>> ./4.6.0-rc5-00034-g2159197-dirty/2016-Jun-22_12h55m43s.log:Score on xml.validation: 2140.02 ops/m
>>
>>