Hi Ali, On Tue, Oct 18, 2016 at 3:57 PM, Ali KIZIL <aliki...@gmail.com> wrote:
> 2016-10-18 22:44 GMT+03:00 Sven C. Dack <sven.c.d...@sky.com>: > > > On 18/10/16 20:26, Ali KIZIL wrote: > > > >> Hi Everyone, > >> > >> Today, I was analyzing memcpy duration in FFmpeg. I noticed that it is > >> taking longer time compared to an optimized SSE, SSE2, MMX, MMX2, AVX or > >> AVX2 based memcpy operation. > >> > >> I tried march=corei7-avx2 compiled FFmpeg version, it does not change > the > >> duration of memcpy operation. > >> I also folowed https://trac.ffmpeg.org/wiki/C > >> ompilationGuide#PerformanceTips > >> .Same result. In addition, I tried gcc 6.2 if gcc if gcc is not > selecting > >> the correct flag. Same result again. > >> > >> This memcpy operations effect the fps decoding (and probably encoding) > >> rates. > >> > >> In a case that uyvy422 to p010 3840x2160 unscaled convertion in > rawvideo, > >> fps rate increased from 44 fps to 52 fps on a Xeon E5 2630 v4. > >> > >> Do I miss anything when compiling FFmpeg for AVX2 or other flag > optimised, > >> or there need a fix in FFmpeg to direct some (or all) memcpy operations > >> to > >> a inherited memcpy operation which can decide flag for optimisation ? > >> Or there is no such need and I am on a wrong path ? > >> > >> (As a side note, FFmpeg works performance on i7 Extreme cores compared > to > >> Xeon v4 processors.) > > > > Could be it's gcc's built-in version. It's been said that libc is > > occasionally better at it than gcc's built-in version. > > > > Use -fno-builtin-memcpy and see what difference it makes. > > I see, tomorrow morning I will give it a try. > Thank you for the good idea. If it increase performance, maybe it will be a > good idea to make a configure option. configure has --extra-cflags=.. and --extra-ldflags=.. options to add custom CC CLI arguments. Ronald _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel