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Date:   Sat, 10 Jul 2021 14:31:09 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Matteo Croce <mcroce@linux.microsoft.com>
Cc:     linux-kernel@vger.kernel.org, Nick Kossifidis <mick@ics.forth.gr>,
        Guo Ren <guoren@kernel.org>,
        Christoph Hellwig <hch@infradead.org>,
        David Laight <David.Laight@aculab.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Emil Renner Berthing <kernel@esmil.dk>,
        Drew Fustini <drew@beagleboard.org>,
        linux-arch@vger.kernel.org,
        Nick Desaulniers <ndesaulniers@google.com>,
        linux-riscv@lists.infradead.org
Subject: Re: [PATCH v2 0/3] lib/string: optimized mem* functions
Message-Id: <20210710143109.fd5062902ef4d5d59e83f5bb@linux-foundation.org>
In-Reply-To: <20210702123153.14093-1-mcroce@linux.microsoft.com>
References: <20210702123153.14093-1-mcroce@linux.microsoft.com>
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On Fri,  2 Jul 2021 14:31:50 +0200 Matteo Croce <mcroce@linux.microsoft.com> wrote:

> From: Matteo Croce <mcroce@microsoft.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?