linux-kernel - Re: [PATCH] riscv: use the generic string routines

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Message-ID: <CAJF2gTTJ8M5FpL4=PDnPQgrrPaLxVhsZCTO2rXqaOm6MEn=gnA@mail.gmail.com>
Date:   Sun, 12 Sep 2021 08:10:27 +0800
From:   Guo Ren <guoren@...nel.org>
To:     Palmer Dabbelt <palmer@...belt.com>
Cc:     Matteo Croce <mcroce@...ux.microsoft.com>,
        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>,
        Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH] riscv: use the generic string routines

On Sat, Sep 11, 2021 at 11:49 AM Palmer Dabbelt <palmer@...belt.com> wrote:
>
> On Thu, 05 Aug 2021 03:31:04 PDT (-0700), mcroce@...ux.microsoft.com wrote:
> > On Wed, Aug 4, 2021 at 10:40 PM Palmer Dabbelt <palmer@...belt.com> wrote:
> >>
> >> On Tue, 03 Aug 2021 09:54:34 PDT (-0700), mcroce@...ux.microsoft.com wrote:
> >> > On Mon, Jul 19, 2021 at 1:44 PM Matteo Croce <mcroce@...ux.microsoft.com> wrote:
> >> >>
> >> >> From: Matteo Croce <mcroce@...rosoft.com>
> >> >>
> >> >> Use the generic routines which handle alignment properly.
> >> >>
> >> >> These are the performances measured on a BeagleV machine for 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
> >> >>
> >> >> TCP throughput with iperf3 gives a similar improvement as well.
> >> >>
> >> >> This is the binary size increase according to bloat-o-meter:
> >> >>
> >> >> add/remove: 0/0 grow/shrink: 4/2 up/down: 432/-36 (396)
> >> >> Function                                     old     new   delta
> >> >> memcpy                                        36     324    +288
> >> >> memset                                        32     148    +116
> >> >> strlcpy                                      116     132     +16
> >> >> strscpy_pad                                   84      96     +12
> >> >> strlcat                                      176     164     -12
> >> >> memmove                                       76      52     -24
> >> >> Total: Before=1225371, After=1225767, chg +0.03%
> >> >>
> >> >> Signed-off-by: Matteo Croce <mcroce@...rosoft.com>
> >> >> Signed-off-by: Emil Renner Berthing <kernel@...il.dk>
> >> >> ---
> >> >
> >> > Hi,
> >> >
> >> > can someone have a look at this change and share opinions?
> >>
> >> This LGTM.  How are the generic string routines landing?  I'm happy to
> >> take this into my for-next, but IIUC we need the optimized generic
> >> versions first so we don't have a performance regression falling back to
> >> the trivial ones for a bit.  Is there a shared tag I can pull in?
> >
> > Hi,
> >
> > I see them only in linux-next by now.
>
> These ended up getting rejected by Linus, so I'm going to hold off on
> this for now.  If they're really out of lib/ then I'll take the C
> routines in arch/riscv, but either way it's an issue for the next
> release.
Agree, we should take the C routine in arch/riscv for common
implementation. If any vendor what custom implementation they could
use the alternative framework in errata for string operations.

-- 
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/