linux-kernel - Re: [PATCH v2 0/3] lib/string: optimized mem* functions

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Message-Id: <20210710143109.fd5062902ef4d5d59e83f5bb@linux-foundation.org>
Date:   Sat, 10 Jul 2021 14:31:09 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Matteo Croce <mcroce@...ux.microsoft.com>
Cc:     linux-kernel@...r.kernel.org, Nick Kossifidis <mick@....forth.gr>,
        Guo Ren <guoren@...nel.org>,
        Christoph Hellwig <hch@...radead.org>,
        David Laight <David.Laight@...lab.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Emil Renner Berthing <kernel@...il.dk>,
        Drew Fustini <drew@...gleboard.org>,
        linux-arch@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v2 0/3] lib/string: optimized mem* functions

On Fri,  2 Jul 2021 14:31:50 +0200 Matteo Croce <mcroce@...ux.microsoft.com> wrote:

> From: Matteo Croce <mcroce@...rosoft.com>
> 
> Rewrite the generic mem{cpy,move,set} so that memory is accessed with
> the widest size possible, but without doing unaligned accesses.
> 
> This was originally posted as C string functions for RISC-V[1], but as
> there was no specific RISC-V code, it was proposed for the generic
> lib/string.c implementation.
> 
> Tested on RISC-V and on x86_64 by undefining __HAVE_ARCH_MEM{CPY,SET,MOVE}
> and HAVE_EFFICIENT_UNALIGNED_ACCESS.
> 
> These are the performances of memcpy() and memset() of a RISC-V machine
> on a 32 mbyte buffer:
> 
> memcpy:
> original aligned:	 75 Mb/s
> original unaligned:	 75 Mb/s
> new aligned:		114 Mb/s
> new unaligned:		107 Mb/s
> 
> memset:
> original aligned:	140 Mb/s
> original unaligned:	140 Mb/s
> new aligned:		241 Mb/s
> new unaligned:		241 Mb/s

Did you record the x86_64 performance?


Which other architectures are affected by this change?