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

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Date:   Fri, 10 Sep 2021 20:49:02 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     mcroce@...ux.microsoft.com
CC:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org,
        Paul Walmsley <paul.walmsley@...ive.com>,
        aou@...s.berkeley.edu, Atish Patra <Atish.Patra@....com>,
        kernel@...il.dk, akira.tsukamoto@...il.com, drew@...gleboard.org,
        bmeng.cn@...il.com, David.Laight@...lab.com, guoren@...nel.org,
        Christoph Hellwig <hch@...radead.org>
Subject:     Re: [PATCH] riscv: use the generic string routines

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.