[PATCH 0/1] __asm_copy_to-from_user: Reduce more byte_copy

From: Akira Tsukamoto <akira.tsukamoto@gmail.com>
To: Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Guenter Roeck <linux@roeck-us.net>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Qiu Wenbo <qiuwenbo@kylinos.com.cn>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Akira Tsukamoto <akira.tsukamoto@gmail.com>,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: [PATCH 0/1] __asm_copy_to-from_user: Reduce more byte_copy
Date: Fri, 30 Jul 2021 22:50:52 +0900	[thread overview]
Message-ID: <65f08f01-d4ce-75c2-030b-f8759003e061@gmail.com> (raw)

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