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    SubjectRe: [PATCH] lib: memmove: Use optimised memcpy if possible
    Hi Dan,

    On 26 November 2017 at 02:10, Dan Carpenter <dan.carpenter@oracle.com> wrote:
    > Paul's original patch should have been separated into two patches to
    > begin with. The patch does two different things and one part goes
    > through the MIPS tree and one part goes through Andrew, probably.

    Okay. I will split his patch into two and send with my modifications.

    > On Sat, Nov 25, 2017 at 10:52:04PM +0530, PrasannaKumar Muralidharan wrote:
    >> Hi,
    >>
    >> On 4 October 2017 at 22:26, PrasannaKumar Muralidharan
    >> <prasannatsmkumar@gmail.com> wrote:
    >> > When there is no overlap between src and dst use optimised memcpy if it
    >> > is available.
    >> >
    >> > Signed-off-by: Paul Burton <paul.burton@imgtec.com>
    >> > Signed-off-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
    >> > ---
    >> > This change is a small part of a patch [1] from Paul Burton. I have
    >> > added his Signed-off by. I do not know whether it is correct. Please let
    >> > me know if it has to be changed, I will send a v2.
    >
    >
    > Sign-off is like signing a legal document. Read
    > Documentation/process/submitting-patches.rst the section about
    > "11) Sign your work - the Developer's Certificate of Origin" for an
    > explanation.
    >
    > So, yeah, Paul provided his s-o-b and it needs to be here as well. But
    > also he maybe should get authorship credit. Just put the first line in
    > the email as:
    >
    > From: Paul Burton <paul.burton@imgtec.com>
    >
    > But that's sort of a trickier thing, so maybe put some explanation that
    > you chopped out a bit from Pauls patch in the changelog:
    >
    > This is part of a patch that Paul Burton wrote
    > https://patchwork.linux-mips.org/patch/14517/
    >
    > I know you put that here, but since it's under the --- cut off it won't
    > be saved in the final git log.

    Sure. Will do.

    >> >
    >> > This patch is boot tested with qemu for MIPS architecture by removing
    >> > mips's memmove routine. This patch does not contain MIPS changes. I
    >> > will try to find out why [1] was not taken already and figure out what
    >> > to do.
    >> >
    >
    > Instead of boot testing, it would be better if we had a benchmark to
    > show it helped speed things up.

    I will try to come up with some reasonable benchmark and post its results.

    >> > 1. https://patchwork.linux-mips.org/patch/14517/
    >> >
    >> > lib/string.c | 11 +++++++++++
    >> > 1 file changed, 11 insertions(+)
    >> >
    >> > diff --git a/lib/string.c b/lib/string.c
    >> > index 9921dc2..462ab7b 100644
    >> > --- a/lib/string.c
    >> > +++ b/lib/string.c
    >> > @@ -825,6 +825,17 @@ void *memmove(void *dest, const void *src, size_t count)
    >> > char *tmp;
    >> > const char *s;
    >> >
    >> > +#ifdef __HAVE_ARCH_MEMCPY
    >> > + /* Use optimised memcpy when there is no overlap */
    >> > + const char *s_end = src + count;
    >> > + const char *d = dest;
    >> > + char *d_end = dest + count;
    >> > +
    >> > + s = src;
    >> > + if ((d_end <= s) || (s_end <= d))
    >> > + return memcpy(dest, src, count);
    >> > +#endif /* __HAVE_ARCH_MEMCPY */
    >> > +
    >> > if (dest <= src) {
    >> > tmp = dest;
    >> > s = src;
    >> > --
    >> > 2.10.0
    >> >
    >>
    >> Is there anything more that I have to do for this patch?
    >>
    >
    > Probably a patch like this needs to go through Andrew. Send it again
    > and CC Andrew Morton <akpm@linux-foundation.org>. It would be nice if
    > we could CC a better list than LKML but I don't know which one... Few
    > people read LKML.

    I will add Andrew. Get maintainer script gave me a small list of email
    id for this. I don't know if there is a better way than using
    get_maintainer.pl.

    > regards,
    > dan carpenter

    Thanks a lot for your time Dan.

    Thanks,
    PrasannaKumar

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