linux-kernel - Re: [PATCH] mm, oom: allow oom reaper to race with exit

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Date:   Tue, 25 Jul 2017 17:23:00 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        David Rientjes <rientjes@...gle.com>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Oleg Nesterov <oleg@...hat.com>,
        Hugh Dickins <hughd@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap

On Tue 25-07-17 18:17:54, Kirill A. Shutemov wrote:
> > before the patch
> > min: 306300.00 max: 6731916.00 avg: 437962.07 std: 92898.30 nr: 100000
> > 
> > after
> > min: 303196.00 max: 5728080.00 avg: 436081.87 std: 96165.98 nr: 100000
> > 
> > The results are well withing noise as I would expect.
> 
> I've silightly modified your test case: replaced cpuid + rdtsc with
> rdtscp. cpuid overhead is measurable in such tight loop.
> 
> 3 runs before the patch:
>    Min. 1st Qu.  Median    Mean 3rd Qu.    Max.
>  177200  205000  212900  217800  223700 2377000
>  172400  201700  209700  214300  220600 1343000
>  175700  203800  212300  217100  223000 1061000
> 
> 3 runs after the patch:
>    Min. 1st Qu.  Median    Mean 3rd Qu.    Max.
>  175900  204800  213000  216400  223600 1989000
>  180300  210900  219600  223600  230200 3184000
>  182100  212500  222000  226200  232700 1473000
> 
> The difference is still measuarble. Around 3%.

what is stdev?
-- 
Michal Hocko
SUSE Labs