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: <20160622111246.GE30154@twins.programming.kicks-ass.net>
Date:	Wed, 22 Jun 2016 13:12:46 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Jirka Hladky <jhladky@...hat.com>
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

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