[FFmpeg-devel] [PATCH 3/3] avformat/mpegts: use av_unlikely for detecting unknown streams

[Carl Eugen Hoyos]

2019-01-25 2:03 GMT+01:00, Marton Balint <cus at passwd.hu>:
>
> On Fri, 25 Jan 2019, Carl Eugen Hoyos wrote:
>
>> 2019-01-24 21:38 GMT+01:00, Marton Balint <cus at passwd.hu>:
>>> Strangely the previous commit caused a slowdown in overall performance
>>> and this fixes it. I used gcc 7.3.1. Does anybody else see this?
>>
>> No, but since this command exists nearly immediately for me
>> I see a 5% deviation even without your patch.
>
> Thanks for checking it. I tested my series on top of
> 1b126ec4087ab5d87d413116bee666495b0d2d3e, and can still reproduce the
> speedup on it. On the other hand, on current git head, I can no longer
> reproduce the speedup. Whatever this is, the fact that using av_unlikely
> fixed it is probably just luck.
>
> So considering the mixed feelings about av_(un)likely in general, I'll
> just drop patch 1 and 3.

I would love to test a command line where it makes a (very) clear
difference, I wonder a little about the claim that it would help
(measurably) on some systems but not others.

Carl Eugen