On Sat, Oct 17, 2015 at 09:30:01PM -0400, Ganesh Ajjanagadde wrote: > Commit 3a0a2f33a6c955823fa4fb12c0b49cd29a496659 claims large performance > advantages for AV_QSORT over libc's qsort. The reason is that I suspect > that libc's qsort (at least on non LTO builds, like the typical FFmpeg config) > can't inline the comparison callback: > https://stackoverflow.com/questions/5290695/is-there-any-way-a-c-c-compiler-can-inline-a-c-callback-function. > AV_QSORT has two things going for it: > 1. The guaranteed inlining of qsort itself. This yields a negligible > boost that may be ignored. > 2. The more serious possibility of potentially allowing the comparison > function to be inlined - this is likely responsible for the large boosts > reported. > > There is a comment explaining that this is a place that could use some > performance improvement. Thus AV_QSORT is used to achieve that. > > Benchmarks deemed unnecessary due to existing claims about AV_QSORT. > Tested with FATE. > > Signed-off-by: Ganesh Ajjanagadde <gajjanaga...@gmail.com> > --- > libavcodec/bitstream.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-)
LGTM thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB The educated differ from the uneducated as much as the living from the dead. -- Aristotle
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