[FFmpeg-devel] [PATCH] all: replace qsort with AV_QSORT

[Ganesh Ajjanagadde]

On Sun, Oct 18, 2015 at 11:01 AM, wm4 <nfxjfg at googlemail.com> wrote:
> On Sun, 18 Oct 2015 10:47:52 -0400
> Ganesh Ajjanagadde <gajjanagadde at gmail.com> wrote:
>
>> Commit e11e32686fdb21aded1ccf70202f1fffe87bb6a2 explains why replacing
>> qsort with AV_QSORT yields performance improvements.
>>
>> This replaces all existing uses of libc's qsort with AV_QSORT.
>>
>> Benchmarks deemed unnecessary due to existing claims about AV_QSORT.
>> Tested with FATE.
>>
>> Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>
>> ---
>>  cmdutils.c                       |  3 ++-
>>  cmdutils_opencl.c                |  3 ++-
>>  ffmpeg.c                         |  3 ++-
>>  libavcodec/aacsbr_template.c     | 14 ++++++++------
>>  libavcodec/huffman.c             |  3 ++-
>>  libavcodec/motion_est_template.c |  3 ++-
>>  libavcodec/utvideodec.c          |  4 ++--
>>  libavcodec/utvideoenc.c          |  5 +++--
>>  libavfilter/f_sendcmd.c          |  3 ++-
>>  libavfilter/vf_deshake.c         |  3 ++-
>>  libavfilter/vf_palettegen.c      |  2 +-
>>  libavfilter/vf_paletteuse.c      |  2 +-
>>  libavfilter/vf_removegrain.c     |  7 ++++---
>>  libavformat/subtitles.c          | 10 +++++++---
>>  libswresample/swresample-test.c  |  3 ++-
>>  tests/checkasm/checkasm.c        |  4 ++--
>>  16 files changed, 44 insertions(+), 28 deletions(-)
>
> By how much does this increase binary code size?
>
> Is it really faster? (libc qsort() could use a better algorithm,
> even if it has to go through indirections.)

Michael has already shown that AV_QSORT is faster. libc's qsort can
easily be looked up: Michael already uses most of the tricks (usage of
stack to avoid recursion, etc). The main benefits come from the
inlining.

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