On Oct 18, 2016 11:08 PM, "Ronald S. Bultje" <rsbul...@gmail.com> wrote: > > 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
Hi Ronald, Yes, I used extra flags to give march=native or march=corei7-avx2. Tomorrow, I will try -fno-builtin-memcpy option with extra-cflag. I will update the topic. Thank you, _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
