[x264-devel] Hyperthreading

[Dennis Munsie]

Thanks for the quick reply -- we ran your test on our system, and found
similar results.  The CPU load issue was tracked down to a faulty CPU
monitor -- even when using 8 threads on a 4 core HT machine, the CPU monitor
reports 50% max usage for some unknown reason at this time.

Thanks again!
dennis

On Thu, Aug 26, 2010 at 1:05 PM, Jason Garrett-Glaser <darkshikari at gmail.com
> wrote:

> On Thu, Aug 26, 2010 at 11:28 AM, Dennis Munsie <dmunsie at gmail.com> wrote:
> > Hi --
> > Does x264 have any support for detecting that it's running on a
> > Hyperthreaded enabled CPU and to only spawn threads for each real CPU?
> I've
> > noticed that on our quad core i7s, we've seen a total of 9 threads when
> > doing slice based threading (for low-latency support) when encoding a
> 720p
> > clip.  Since the load on the machine appears to be 50% overall and it
> > doesn't get slower when we turn off HT, it appears those extra threads
> are
> > unable to get the resources to actually run in parallel with the 4 other
> > threads.
> > I am using x264 as a library in my own program -- so it may be that I've
> > just missed a configuration option that I should've set.
> > Thanks!
> > dennis
>
> Our testing strongly suggests that the number of virtual cores is
> optimal when using sliced threads, even when HT is on:
>
>
> http://saintdevelopment.com/benchmarks/bfs-vs-cfs/720p_i7/2.6.32-720p-0lat-vf-nob.png
>
> Dark Shikari
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-- 
dennis
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