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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Tue, 27 Jun 2023 15:25:41 -0700
Message-ID: <CAHk-=wiQEj1cP7tnQ6Uw1jjFYnZmMdNgodga3b+rw98vBBvENg@mail.gmail.com>
Subject: Re: [GIT PULL] x86/misc for 6.5
To:     Arjan van de Ven <arjan@linux.intel.com>
Cc:     Borislav Petkov <bp@alien8.de>,
        Noah Goldstein <goldstein.w.n@gmail.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        x86-ml <x86@kernel.org>, lkml <linux-kernel@vger.kernel.org>
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On Tue, 27 Jun 2023 at 14:44, Arjan van de Ven <arjan@linux.intel.com> wrote:
>
> fwiw long flights and pools have a relation; I made a userspace testbench
> for this some time ago: https://github.com/fenrus75/csum_partial
> in case one would actually WANT to test ;)

Hmm.

I don't know what the rules are - and some of the functions you test
seem actively buggy (ie not handling alignment right etc).

But on my machine I get:

  02:   8.6 /  10.4 cycles (e29e455e) Upcoming linux kernel version
  04:   8.6 /  10.4 cycles (e29e455e) Specialized to size 40
  06:   7.7 /   9.5 cycles (e29e455e) New version
  22:   8.7 /   9.6 cycles (e29e455e) Odd-alignment handling removed
 ...

which would seem to mean that my code ("New version") is doing well.

It does do worse on the "odd alignment" case:

  03: 15.5 /  17.8 cycles (00006580) Upcoming linux kernel version
  05: 15.5 /  17.8 cycles (00006580) Specialized to size 40
  07: 16.6 /  19.5 cycles (0000bc29) New version
  23:   8.8 /   8.6 cycles (1de29e47) Odd-alignment handling removed
 ...

I just hacked the code into the benchmark without looking too closely
at what is going on, so no guarantees.

         Linus