Messages in this thread | | | From | Matteo Croce <> | Subject | [PATCH v2 0/3] lib/string: optimized mem* functions | Date | Fri, 2 Jul 2021 14:31:50 +0200 |
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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
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