linux-ext4 - Re: [fsnotify] 4c40d6efc8: unixbench.score -3.3% regression

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Date:   Tue, 3 Aug 2021 19:19:04 +0300
From:   Amir Goldstein <amir73il@...il.com>
To:     Oliver Sang <oliver.sang@...el.com>
Cc:     Gabriel Krisman Bertazi <krisman@...labora.com>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org,
        ying.huang@...el.com, feng.tang@...el.com,
        zhengjun.xing@...ux.intel.com, Jan Kara <jack@...e.com>,
        "Darrick J. Wong" <djwong@...nel.org>,
        Theodore Tso <tytso@....edu>,
        Dave Chinner <david@...morbit.com>,
        David Howells <dhowells@...hat.com>,
        Khazhismel Kumykov <khazhy@...gle.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Ext4 <linux-ext4@...r.kernel.org>, kernel@...labora.com,
        Mel Gorman <mgorman@...hsingularity.net>,
        0day robot <lkp@...el.com>
Subject: Re: [fsnotify] 4c40d6efc8: unixbench.score -3.3% regression

> > Oliver,
> >
> > Would it be possible to request a re-test with the branch:
> > https://github.com/amir73il/linux fsnotify-perf
> >
> > The patch at the tip of that branch is the one this regression report
> > has blamed.
> >
> > My expectation is that the patch at fsnotify-perf^ ("fsnotify: optimize the
> > case of no marks of any type") will improve performance of the test case
> > compared to baseline (v5.14-rc3) and that the patch at the tip of fsnotify-perf
> > would not regress performance.
>
> we tested this branch and the results meet your expectation.
>
> fsnotify-perf^ improves performance comparing to v5.14-rc3. tip is a little worse
> than its parent (-3.3%), but still better than v5.14-rc3.
>
> below is detail data.
>
>
> =========================================================================================
> compiler/cpufreq_governor/kconfig/nr_task/rootfs/runtime/tbox_group/test/testcase/ucode:
>   gcc-9/performance/x86_64-rhel-8.3/1/debian-10.4-x86_64-20200603.cgz/300s/lkp-csl-2sp4/pipe/unixbench/0x4003006
>
> commit:
>   v5.14-rc3
>   23050d041 ("fsnotify: optimize the case of no marks of any type")
>   7446ba772 ("fsnotify: pass arguments of fsnotify() in struct fsnotify_event_info")
>
>        v5.14-rc3 23050d0419441a02185e4ed5170 7446ba772ae107ab937cd04e880
> ---------------- --------------------------- ---------------------------
>          %stddev     %change         %stddev     %change         %stddev
>              \          |                \          |                \
>       1562            +8.0%       1688            +4.5%       1633        unixbench.score

Hi Oliver,

Thanks a lot for testing!

I don't know what to make of the (-3.3%) degradation because I was expecting
that fsnotify-perf^ would optimize out the calls to fsnotify() and fsnotify-perf
only changes code from fsnotify() and below.

But I guess it doesn't matter much as Gabriel said, its a cleanup patch and
we can drop it.

But now that I have this report I can post the fsnotify-perf^ patches :-)

Thanks,
Amir.