linux-kernel - [PATCH v4 0/3] riscv: optimized mem* functions

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Message-Id: <20210919192104.98592-1-mcroce@linux.microsoft.com>
Date:   Sun, 19 Sep 2021 21:21:01 +0200
From:   Matteo Croce <mcroce@...ux.microsoft.com>
To:     linux-riscv@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Atish Patra <atish.patra@....com>,
        Emil Renner Berthing <kernel@...il.dk>,
        Akira Tsukamoto <akira.tsukamoto@...il.com>,
        Drew Fustini <drew@...gleboard.org>,
        Bin Meng <bmeng.cn@...il.com>,
        David Laight <David.Laight@...lab.com>,
        Guo Ren <guoren@...nel.org>, Christoph Hellwig <hch@....de>
Subject: [PATCH v4 0/3] riscv: optimized mem* functions

From: Matteo Croce <mcroce@...rosoft.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.

A further improvement could be to use multiple read and writes as the
assembly version was trying to do.

Tested on a BeagleV Starlight with a SiFive U74 core, where the
improvement is noticeable.

v3 -> v4:
- incorporate changes from proposed generic version:
  https://lore.kernel.org/lkml/20210617152754.17960-1-mcroce@linux.microsoft.com/

v2 -> v3:
- alias mem* to __mem* and not viceversa
- use __alias instead of a tail call

v1 -> v2:
- reduce the threshold from 64 to 16 bytes
- fix KASAN build
- optimize memset

Matteo Croce (3):
  riscv: optimized memcpy
  riscv: optimized memmove
  riscv: optimized memset

 arch/riscv/include/asm/string.h |  18 ++--
 arch/riscv/kernel/Makefile      |   1 -
 arch/riscv/kernel/riscv_ksyms.c |  17 ----
 arch/riscv/lib/Makefile         |   4 +-
 arch/riscv/lib/memcpy.S         | 108 ----------------------
 arch/riscv/lib/memmove.S        |  64 -------------
 arch/riscv/lib/memset.S         | 113 -----------------------
 arch/riscv/lib/string.c         | 154 ++++++++++++++++++++++++++++++++
 8 files changed, 164 insertions(+), 315 deletions(-)
 delete mode 100644 arch/riscv/kernel/riscv_ksyms.c
 delete mode 100644 arch/riscv/lib/memcpy.S
 delete mode 100644 arch/riscv/lib/memmove.S
 delete mode 100644 arch/riscv/lib/memset.S
 create mode 100644 arch/riscv/lib/string.c

-- 
2.31.1