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: <3abcc9e2-3598-1264-4ba7-8557b35bbc6f@gmail.com>
Date:	Wed, 22 Jun 2016 09:37:10 +0200
From:	Branimir Maksimovic <branimir.maksimovic@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: Re: Kernel 4.7rc3 - Performance drop 30-40% for SPECjbb2005 and
 SPECjvm2008 benchmarks against 4.6 kernel

Could it be related to this:

https://www.phoronix.com/scan.php?page=news_item&px=P-State-Possible-4.6-Regression


On Thu, 16 Jun 2016 18:40:01 +0200
Jirka Hladky <jhladky@...hat.com> wrote:

 > Hello,
 >
 > we see performance drop 30-40% for SPECjbb2005 and SPECjvm2008
 > benchmarks starting from 4.7.0-0.rc0 kernel compared to 4.6 kernel.
 >
 > We have tested kernels 4.7.0-0.rc1 and 4.7.0-0.rc3 and these are as
 > well affected.
 >
 > We have observed the drop on variety of different x86_64 servers with
 > different configuration (different CPU models, RAM sizes, both with
 > Hyper Threading ON and OFF, different NUMA configurations (2 and 4
 > NUMA nodes)
 >
 > Linpack and Stream benchmarks do not show any performance drop.
 >
 > The performance drop increases with higher number of threads. The
 > maximum number of threads in each benchmark is the same as number of
 > CPUs.
 >
 > We have opened a BZ to track the progress:
 > https://bugzilla.kernel.org/show_bug.cgi?id=120481
 >
 > You can find more details along with graphs and tables there.
 >
 > Do you have any hints which commit should we try to reverse?
 >
 > Thanks a lot!
 > Jirka