linux-kernel - Re: [LKP] [lkp] [mm, oom] faad2185f4: vm-scalability.throughput -11.8% regression

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Date:	Wed, 27 Apr 2016 11:17:19 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	"Huang, Ying" <ying.huang@...el.com>
Cc:	kernel test robot <xiaolong.ye@...el.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	Hillf Danton <hillf.zj@...baba-inc.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Mel Gorman <mgorman@...e.de>,
	David Rientjes <rientjes@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>, lkp@...org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [LKP] [lkp] [mm, oom] faad2185f4: vm-scalability.throughput
 -11.8% regression

On Wed 27-04-16 16:44:31, Huang, Ying wrote:
> Michal Hocko <mhocko@...nel.org> writes:
> 
> > On Wed 27-04-16 16:20:43, Huang, Ying wrote:
> >> Michal Hocko <mhocko@...nel.org> writes:
> >> 
> >> > On Wed 27-04-16 11:15:56, kernel test robot wrote:
> >> >> FYI, we noticed vm-scalability.throughput -11.8% regression with the following commit:
> >> >
> >> > Could you be more specific what the test does please?
> >> 
> >> The sub-testcase of vm-scalability is swap-w-rand.  An RAM emulated pmem
> >> device is used as a swap device, and a test program will allocate/write
> >> anonymous memory randomly to exercise page allocation, reclaiming, and
> >> swapping in code path.
> >
> > Can I download the test with the setup to play with this?
> 
> There are reproduce steps in the original report email.
> 
> To reproduce:
> 
>         git clone git://git.kernel.org/pub/scm/linux/kernel/git/wfg/lkp-tests.git
>         cd lkp-tests
>         bin/lkp install job.yaml  # job file is attached in this email
>         bin/lkp run     job.yaml
> 
> 
> The job.yaml and kconfig file are attached in the original report email.

Thanks for the instructions. My bad I have overlooked that in the
initial email. I have checked the configuration file and it seems rather
hardcoded for a particular HW. It expects a machine with 128G and
reserves 96G!4G which might lead to different amount of memory in the
end depending on the particular memory layout.

Before I go and try to recreate a similar setup, how stable are the
results from this test. Random access pattern sounds like rather
volatile to be consider for a throughput test. Or is there any other
side effect I am missing and something fails which didn't use to
previously.
-- 
Michal Hocko
SUSE Labs