[x264-devel] Re: x264 & slices

[Måns Rullgård]

ollo.diab at gmx.de writes:

> Hi Tuukka,
>
> I tried recent x264 enabled mencoder to trancode a HDTV mpeg2 file to H.264
> avi on a Quad Opteron system running RedHat Enterprise 3 64bit. x264 got
> build with pthread enabled.
>
> Now if I run mencoder with default x264 encoder settings and add the
> threads=1 parameter, then I get about 5fps, fine. But the odd thing is, all
> 4 CPUs are busy at around 25%. Then I tried threads=2, the rate got to 7fps
> and all 4 CPUs are running at 35% load. With threads=3 the rate goes to 8fps
> and with threads=4 goes to 9fps while all CPUs run at 50% load.
>
> Somehow I was under the impression the thread parameter more or less defines
> how many CPUs get used. So I expected to see a load of 100% on a single CPU
> with threads=1 and on 2 CPUs with threads=2 and so on.

The OS moves tasks between CPUs for various reasons.  This is what you
are seeing.

-- 
Måns Rullgård
mru at inprovide.com

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