Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8;
 format=flowed
Content-Transfer-Encoding: 8bit
Date:   Tue, 22 Jun 2021 04:09:14 +0300
From:   Nick Kossifidis <mick@ics.forth.gr>
To:     Matteo Croce <mcroce@linux.microsoft.com>
Cc:     linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-arch@vger.kernel.org,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Atish Patra <atish.patra@wdc.com>,
        Emil Renner Berthing <kernel@esmil.dk>,
        Akira Tsukamoto <akira.tsukamoto@gmail.com>,
        Drew Fustini <drew@beagleboard.org>,
        Bin Meng <bmeng.cn@gmail.com>,
        David Laight <David.Laight@aculab.com>,
        Guo Ren <guoren@kernel.org>
Subject: Re: [PATCH v3 0/3] riscv: optimized mem* functions
Organization: FORTH
In-Reply-To: <20210617152754.17960-1-mcroce@linux.microsoft.com>
References: <20210617152754.17960-1-mcroce@linux.microsoft.com>
Message-ID: <e968312557f147af1e5efb341eeef0ad@mailhost.ics.forth.gr>
User-Agent: Roundcube Webmail/1.3.16
Precedence: bulk

Hello Matteo,

Στις 2021-06-17 18:27, Matteo Croce έγραψε:
> From: Matteo Croce <mcroce@microsoft.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/.