linux-kernel - Re: [PATCH 0/1] __asm_copy_to-from_user: Reduce more byte

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Date:   Thu, 12 Aug 2021 20:01:29 +0900
From:   Akira Tsukamoto <akira.tsukamoto@...il.com>
To:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Qiu Wenbo <qiuwenbo@...inos.com.cn>,
        Albert Ou <aou@...s.berkeley.edu>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/1] __asm_copy_to-from_user: Reduce more byte_copy

Hi Guenter, Geert and Qiu,

Would you mind testing this patch?
Thanks,

Akira

On 7/30/2021 10:50 PM, Akira Tsukamoto wrote:
> Adding none unrolling word_copy, which is used if the size is smaller
> than 9*SZREG.
> 
> This patch is based on Palmer's past comment.
>> My guess is that some workloads will want some smaller unrolling factors,
> 
> It will reduce the number of slow byte_copy being used when the 
> size is small.
> 
> Have tested on qemu rv32, qemu rv64 and beaglev beta board.
> 
> In the future, I am planning to convert uaccess.S to inline assembly 
> in .c file. Then it will be easier to optimize on both in-order core and
> out-of-order core with #ifdef macro in c.
> 
> Akira Tsukamoto (1):
>   riscv: __asm_copy_to-from_user: Improve using word copy if size <
>     9*SZREG
> 
>  arch/riscv/lib/uaccess.S | 46 ++++++++++++++++++++++++++++++++++++----
>  1 file changed, 42 insertions(+), 4 deletions(-)
>