linux-kernel - Re: [PATCH v3 0/3] riscv: optimized mem* functions

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Message-ID: <e968312557f147af1e5efb341eeef0ad@mailhost.ics.forth.gr>
Date:   Tue, 22 Jun 2021 04:09:14 +0300
From:   Nick Kossifidis <mick@....forth.gr>
To:     Matteo Croce <mcroce@...ux.microsoft.com>
Cc:     linux-riscv@...ts.infradead.org, linux-kernel@...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>,
        Emil Renner Berthing <kernel@...il.dk>,
        Akira Tsukamoto <akira.tsukamoto@...il.com>,
        Drew Fustini <drew@...gleboard.org>,
        Bin Meng <bmeng.cn@...il.com>,
        David Laight <David.Laight@...lab.com>,
        Guo Ren <guoren@...nel.org>
Subject: Re: [PATCH v3 0/3] riscv: optimized mem* functions

Hello Matteo,

Στις 2021-06-17 18:27, Matteo Croce έγραψε:
> From: Matteo Croce <mcroce@...rosoft.com>
> 
> Replace the assembly mem{cpy,move,set} with C equivalent.
> 
> Try to access RAM with the largest bit width possible, but without
> doing unaligned accesses.
> 
> Tested on a BeagleV Starlight with a SiFive U74 core, where the
> improvement is noticeable.
> 

There are already generic C implementations for memcpy/memmove/memset at 
https://elixir.bootlin.com/linux/v5.13-rc7/source/lib/string.c#L871 but 
are doing one byte at a time, I suggest you update them to do 
word-by-word copy instead of introducing yet another memcpy/memmove C 
implementation on arch/riscv/.