linux-kernel - Re: [PATCH v1] x86/lib: Optimize 8x loop and memory clobbers in csum

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Message-ID: <CANn89iJxMhGfp364rPu6p_ZLrKnM1qWF_NWrw4_oL_KG+piByg@mail.gmail.com>
Date:   Fri, 26 Nov 2021 10:27:06 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     Noah Goldstein <goldstein.w.n@...il.com>
Cc:     tglx@...utronix.de, mingo@...hat.com,
        Borislav Petkov <bp@...en8.de>, dave.hansen@...ux.intel.com,
        X86 ML <x86@...nel.org>, hpa@...or.com, peterz@...radead.org,
        alexanderduyck@...com, open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] x86/lib: Optimize 8x loop and memory clobbers in csum_partial.c

On Fri, Nov 26, 2021 at 10:17 AM Noah Goldstein <goldstein.w.n@...il.com> wrote:
>

>
> Makes sense. Although if you inline I think you definitely will want a more
> conservative clobber than just "memory". Also I think with 40 you also will
> get some value from two counters.
>
> Did you see the number/question I posted about two accumulators for 32
> byte case?
> Its a judgement call about latency vs throughput that I don't really have an
> answer for.
>

The thing I do not know is if using more units would slow down the
hyper thread ?

Would using ADCX/ADOX would be better in this respect ?