From: Matteo Croce <mcroce@linux.microsoft.com>
To: linux-kernel@vger.kernel.org, Nick Kossifidis <mick@ics.forth.gr>,
Guo Ren <guoren@kernel.org>,
Christoph Hellwig <hch@infradead.org>,
David Laight <David.Laight@aculab.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Emil Renner Berthing <kernel@esmil.dk>,
Drew Fustini <drew@beagleboard.org>
Cc: linux-arch@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Nick Desaulniers <ndesaulniers@google.com>,
linux-riscv@lists.infradead.org
Subject: [PATCH v2 0/3] lib/string: optimized mem* functions
Date: Fri, 2 Jul 2021 14:31:50 +0200 [thread overview]
Message-ID: <20210702123153.14093-1-mcroce@linux.microsoft.com> (raw)
From: Matteo Croce <mcroce@microsoft.com>
Rewrite the generic mem{cpy,move,set} so that memory is accessed with
the widest size possible, but without doing unaligned accesses.
This was originally posted as C string functions for RISC-V[1], but as
there was no specific RISC-V code, it was proposed for the generic
lib/string.c implementation.
Tested on RISC-V and on x86_64 by undefining __HAVE_ARCH_MEM{CPY,SET,MOVE}
and HAVE_EFFICIENT_UNALIGNED_ACCESS.
These are the performances of memcpy() and memset() of a RISC-V machine
on a 32 mbyte buffer:
memcpy:
original aligned: 75 Mb/s
original unaligned: 75 Mb/s
new aligned: 114 Mb/s
new unaligned: 107 Mb/s
memset:
original aligned: 140 Mb/s
original unaligned: 140 Mb/s
new aligned: 241 Mb/s
new unaligned: 241 Mb/s
The size increase is negligible:
$ scripts/bloat-o-meter vmlinux.orig vmlinux
add/remove: 0/0 grow/shrink: 4/1 up/down: 427/-6 (421)
Function old new delta
memcpy 29 351 +322
memset 29 117 +88
strlcat 68 78 +10
strlcpy 50 57 +7
memmove 56 50 -6
Total: Before=8556964, After=8557385, chg +0.00%
These functions will be used for RISC-V initially.
[1] https://lore.kernel.org/linux-riscv/20210617152754.17960-1-mcroce@linux.microsoft.com/
Matteo Croce (3):
lib/string: optimized memcpy
lib/string: optimized memmove
lib/string: optimized memset
lib/string.c | 130 ++++++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 113 insertions(+), 17 deletions(-)
--
2.31.1
next reply other threads:[~2021-07-02 12:32 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-02 12:31 Matteo Croce [this message]
2021-07-02 12:31 ` [PATCH v2 1/3] lib/string: optimized memcpy Matteo Croce
2021-07-02 14:37 ` Ben Dooks
2021-07-02 14:44 ` Matteo Croce
2021-07-02 12:31 ` [PATCH v2 2/3] lib/string: optimized memmove Matteo Croce
2021-07-02 12:31 ` [PATCH v2 3/3] lib/string: optimized memset Matteo Croce
2021-07-10 21:31 ` [PATCH v2 0/3] lib/string: optimized mem* functions Andrew Morton
2021-07-10 23:07 ` Matteo Croce
2021-07-12 8:15 ` David Laight
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