linux-kernel - Re: [PATCH 1/3] riscv: optimized memcpy

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Message-ID: <CANBLGcxi2mEA5MnV-RL2zFpB2T+OytiHyOLKjOrMXgmAh=fHAw@mail.gmail.com>
Date:   Tue, 15 Jun 2021 18:12:31 +0200
From:   Emil Renner Berthing <kernel@...il.dk>
To:     Bin Meng <bmeng.cn@...il.com>
Cc:     David Laight <David.Laight@...lab.com>,
        Gary Guo <gary@...yguo.net>,
        Matteo Croce <mcroce@...ux.microsoft.com>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Atish Patra <atish.patra@....com>,
        Akira Tsukamoto <akira.tsukamoto@...il.com>,
        Drew Fustini <drew@...gleboard.org>
Subject: Re: [PATCH 1/3] riscv: optimized memcpy

On Tue, 15 Jun 2021 at 15:29, Bin Meng <bmeng.cn@...il.com> wrote:
> ...
> Yes, Gary Guo sent one patch long time ago against the broken assembly
> version, but that patch was still not applied as of today.
> https://patchwork.kernel.org/project/linux-riscv/patch/20210216225555.4976-1-gary@garyguo.net/
>
> I suggest Matteo re-test using Gary's version.

That's a good idea, but if you read the replies to Gary's original patch
https://lore.kernel.org/linux-riscv/20210216225555.4976-1-gary@garyguo.net/
.. both Gary, Palmer and David would rather like a C-based version.
This is one attempt at providing that.

> > I'm surprised IP_NET_ALIGN isn't set to 2 to try to
> > avoid all these misaligned copies in the network stack.
> > Although avoiding 8n+4 aligned data is rather harder.
> >
> > Misaligned copies are just best avoided - really even on x86.
> > The 'real fun' is when the access crosses TLB boundaries.
>
> Regards,
> Bin