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.) >> >> Kind Regards, >> Ali KIZIL >> _______________________________________________ >> ffmpeg-devel mailing list >> ffmpeg-devel@ffmpeg.org >> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel >> > > 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. > > > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
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. Kind Regards, _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel