[x264-devel] Re: x264 & slices

[Måns Rullgård]

Tuukka Toivonen said:
> On Wed, 17 Aug 2005 ollo.diab at gmx.de wrote:
>
>>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.
>
> Sorry for not answering your first mail, but you really shouldn't
> mail directly me about generic x264 questions, but on this list...
> (I have nothing to do with the threading support).
>
>>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.
>
> Anyway, how can you see how busy each CPU is? My top on Debian
> box doesn't display per-CPU busyness, if I remember correctly...

Try pressing 1.  In recent versions of top, that toggles between total
and per-CPU stats.

>>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.
>
> It defines how many threads to use. Generally OS should schedule
> the same thread always on the same CPU, because that's more efficient...
> And Linux should do this, maybe your monitoring tool isn't
> displaying loads correctly?

Linux moves tasks around quite a bit, unless they have been specifically
pinned to a particular CPU.

-- 
Måns Rullgård
mru at inprovide.com

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