Re: [PATCH 3/4] diffcore-pickaxe: further refactor count_match()

[Junio C Hamano <gitster@pobox.com>]

Junio C Hamano <gitster@pobox.com> writes:

> René Scharfe <rene.scharfe@lsrfire.ath.cx> writes:
> ...
>> In any case, there is also memmem(), which uses the same fast algorithm
>> as strstr() in recent glibc versions.  Like this?
>
> Thanks; it would be nice to bench this change.

With memmem() patch applied on top of [1-4/4], the same test as described
in the commit log message of [4/4] which was:

    $ STRING='Ensure that the real time constraints are schedulable.'
    $ git log -S"$STRING" HEAD -- kernel/sched.c >/dev/null

    (Before the patch, best of 5 runs)
    5.59user 0.15system 0:05.74elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
    0inputs+0outputs (0major+39956minor)pagefaults 0swaps

    (After the patch, best of 5 runs)
    3.04user 0.17system 0:03.23elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
    0inputs+0outputs (0major+49697minor)pagefaults 0swaps

    The file "kernel/sched.c" has roughly 900 changes applied to it, and over
    its lifetime, it has grown from 5kB to 9kB in size.  I'd expect a larger
    file may see a bigger performance boost.

(With memmem() patch, best of 5 runs)
2.46user 0.15system 0:02.62elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+49698minor)pagefaults 0swaps