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

From: Jirka Hladky <jhladky@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
	Kamil Kolakowski <kkolakow@redhat.com>
Subject: Re: Kernel 4.7rc3 - Performance drop 30-40% for SPECjbb2005 and SPECjvm2008 benchmarks against 4.6 kernel
Date: Wed, 22 Jun 2016 14:37:14 +0200	[thread overview]
Message-ID: <CAE4VaGCqPS3ne6MqtwAVQYRBchzL_fQ0nMvRZBYDOWe8hVG__A@mail.gmail.com> (raw)
In-Reply-To: <20160622111246.GE30154@twins.programming.kicks-ass.net>

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@infradead.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@intel.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
>
>