[FFmpeg-devel] swscale/rgb2rgb : add X86_64 SIMD (SSSE3 and AVX2) for shuffly_bytes func
Carl Eugen Hoyos
ceffmpeg at gmail.com
Sun Mar 18 18:53:02 EET 2018
2018-03-18 17:46 GMT+01:00, Martin Vignali <martin.vignali at gmail.com>:
> 2018-03-18 17:37 GMT+01:00 Paul B Mahol <onemda at gmail.com>:
>> On 3/18/18, Nicolas George <george at nsup.org> wrote:
>> > Martin Vignali (2018-03-18):
>> >> I run the test again with a bigger width (512 instead of 128)
>> >> This is my result :
>> >> shuffle_bytes_0321_c: 128.6
>> >> shuffle_bytes_0321_ssse3: 41.6
>> >> shuffle_bytes_0321_avx2: 23.4
>> > IIUC, these benchmarks are expressed in CPU cycles. But what James says
>> > is that it can cause the CPU frequency to be throttled: if that happens,
>> > less cycles can use more time, and even worse, cause other unrelated to
>> > take more time. A benchmark in actual time and typical use case would be
>> > needed to decide.
>> Yes, always also test overall with typical code usecase.
> I tested it using a "benchmark" command line, who test two shuffle func
> ./ffmpeg -benchmark -f lavfi -i rgbtestsrc=size=3840x2160:duration=10 -vf
> format=argb,format=rgba -f null -
> With the patch :
> bench: utime=3.611s
> With only SSSE 3 (disable AVX2 part), i have similar result.
Indicating James' original comment that the avx2 optimization
makes no sense is correct?
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