netdev - Re: [PATCH v2] x86/csum: rewrite csum

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Date:   Sat, 13 Nov 2021 08:43:49 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        netdev <netdev@...r.kernel.org>, x86@...nel.org,
        Alexander Duyck <alexander.duyck@...il.com>,
        Andrew Cooper <andrew.cooper3@...rix.com>
Subject: Re: [PATCH v2] x86/csum: rewrite csum_partial()

On Fri, Nov 12, 2021 at 09:23:39AM -0800, Eric Dumazet wrote:
> On Fri, Nov 12, 2021 at 8:45 AM Peter Zijlstra <peterz@...radead.org> wrote:
> >
> 
> >
> > Looks nice, happen to have shiny perf numbers to show how awesome it it?
> > :-)
> 
> On a networking load on cascadlake, line rate received on a single thread, I see
> perf -e cycles:pp -C <cpu>
> 
> Before:
>        4.16%  [kernel]       [k] csum_partial
> After:
>         0.83%  [kernel]       [k] csum_partial
> 
> If run in a loop 1,000,000 times,
> 
> Before:
>        26,922,913      cycles                    # 3846130.429 GHz
>         80,302,961      instructions              #    2.98  insn per
> cycle
>         21,059,816      branches                  # 3008545142.857
> M/sec
>              2,896      branch-misses             #    0.01% of all
> branches
> After:
>         17,960,709      cycles                    # 3592141.800 GHz
>         41,292,805      instructions              #    2.30  insn per
> cycle
>         11,058,119      branches                  # 2211623800.000
> M/sec
>              2,997      branch-misses             #    0.03% of all
> branches
> 
> Thanks for your help !

I've added these numbers to the Changelog and will queue the patch in
x86/core once -rc1 happens.

Thanks!