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: <CAE4VaGACT2XO4woXaHRbPi6bpkovr33oSVBrHqTimNgodSLtug@mail.gmail.com>
Date:	Wed, 22 Jun 2016 11:52:45 +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

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?

Thanks a lot!
Jirka


On Wed, Jun 22, 2016 at 9:54 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Wed, Jun 22, 2016 at 09:49:41AM +0200, Peter Zijlstra wrote:
>> On Wed, Jun 22, 2016 at 09:16:01AM +0200, Peter Zijlstra wrote:
>> > WTF a benchmark needs that crap is beyond me, but whatever, I have
>> > numbers.
>>
>> Oh, shaft me harder, its XML shite :/ How is a sane person ever going to
>> get numbers out.
>>
>> I'm >.< close to giving up on this site and declaring the thing
>> -EDONTCARE.
>
> OK, done.. have a look at this:
>
>
> /tmp/SPECjvm2008/compiler.compiler/compiler/src/share/classes/javax/lang/model/element/Name.java:54: cannot access java.lang.CharSequence
> bad class file: spec.benchmarks.compiler.SpecFileManager$CachedFileObject@...6fce6
> bad constant pool tag: 18 at 10
> Please remove or make sure it appears in the correct subdirectory of the classpath.
> public interface Name extends CharSequence {
>                               ^
> ERROR: compiler exit code: 1
>
> Warmup (120s) begins: Wed Jun 22 09:45:33 CEST 2016
> /tmp/SPECjvm2008/compiler.compiler/compiler/src/share/classes/javax/lang/model/element/Name.java:54: cannot access java.lang.CharSequence
> bad class file: spec.benchmarks.compiler.SpecFileManager$CachedFileObject@...6fce6
> bad constant pool tag: 18 at 10
> Please remove or make sure it appears in the correct subdirectory of the classpath.
> public interface Name extends CharSequence {
>                               ^
> /tmp/SPECjvm2008/compiler.compiler/compiler/src/share/classes/javax/lang/model/element/Name.java:54: cannot access java.lang.CharSequence
> bad class file: spec.benchmarks.compiler.SpecFileManager$CachedFileObject@...6fce6
> bad constant pool tag: 18 at 10
> Please remove or make sure it appears in the correct subdirectory of the classpath.
>
>
>
> Clearly this stuff just isn't made to be used.
>
>
> /me goes do something useful.