Re: [PATCH v2 0/3] lib/string: optimized mem* functions

[Andrew Morton]

On Fri,  2 Jul 2021 14:31:50 +0200 Matteo Croce <mcroce@xxxxxxxxxxxxxxxxxxx> wrote:

> From: Matteo Croce <mcroce@xxxxxxxxxxxxx>
> 
> 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

Did you record the x86_64 performance?


Which other architectures are affected by this change?