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References: <202310172247.b9959bd4-oliver.sang@intel.com> <2023101759-front-ember-6354@gregkh>
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From:   Max Kellermann <max.kellermann@ionos.com>
Date:   Wed, 18 Oct 2023 12:01:45 +0200
Message-ID: <CAKPOu+8r1QpFUCyMMS04GOi-+HqM7-dxR4JcoLXfvXARobbZDA@mail.gmail.com>
Subject: Re: [linux-next:master] [drivers/char/mem] 1b057bd800:
 stress-ng.splice.ops_per_sec -99.8% regression
To:     Oliver Sang <oliver.sang@intel.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        oe-lkp@lists.linux.dev, lkp@intel.com,
        Linux Memory Management List <linux-mm@kvack.org>,
        linux-kernel@vger.kernel.org, ying.huang@intel.com,
        feng.tang@intel.com, fengwei.yin@intel.com
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On Wed, Oct 18, 2023 at 9:07=E2=80=AFAM Oliver Sang <oliver.sang@intel.com>=
 wrote:
> it found a (very big) regression comparing to parent commit.
>
> 19e3e6cdfdc73400 1b057bd800c3ea0c926191d7950
> ---------------- ---------------------------
>          %stddev     %change         %stddev
>              \          |                \
>   12433266           -99.8%      22893 =C4=85  3%  stress-ng.splice.ops_p=
er_sec

Oliver, how is it possible that we have three times the throughput
(MB_per_sec) at 1/500ths the ops?