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

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Message-ID: <65f08f01-d4ce-75c2-030b-f8759003e061@gmail.com>
Date:   Fri, 30 Jul 2021 22:50:52 +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>,
        Akira Tsukamoto <akira.tsukamoto@...il.com>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH 0/1] __asm_copy_to-from_user: Reduce more byte_copy

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(-)

-- 
2.17.1