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

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Date:   Fri, 8 Oct 2021 03:39:55 +0200
From:   Matteo Croce <mcroce@...ux.microsoft.com>
To:     Palmer Dabbelt <palmer@...belt.com>
Cc:     linux-riscv <linux-riscv@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Paul Walmsley <paul.walmsley@...ive.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: Re: [PATCH v4 0/3] riscv: optimized mem* functions

On Fri, Oct 8, 2021 at 3:26 AM Palmer Dabbelt <palmer@...belt.com> wrote:
>
> On Sun, 19 Sep 2021 12:21:01 PDT (-0700), mcroce@...ux.microsoft.com wrote:
> > 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
>
> Thanks.  These generally look good, but they're failing to build for me.
> I'm getting errors along the lines of
>
>     arch/riscv/lib/string.c:89:7: error: inlining failed in call to ‘always_inline’ ‘memcpy’: function body can be overwritten at link time
>        89 | void *memcpy(void *dest, const void *src, size_t count) __weak __alias(__memcpy);      |       ^~~~~~
>     arch/riscv/lib/string.c:99:10: note: called from here
>        99 |   return memcpy(dest, src, count);
>           |          ^~~~~~~~~~~~~~~~~~~~~~~~
>
> I'm still a bit behind on email so I'm going to keep going through
> patches, but if there's no v5 by the time I get back here then I'll take
> a look.

I've sent a v5 here:

https://lore.kernel.org/linux-riscv/20210929172234.31620-1-mcroce@linux.microsoft.com/

Regards,
-- 
per aspera ad upstream