[FFmpeg-user] maximum CPU utilization with ffmpeg and libx264

[Richard Buteau]

> -----Original Message-----
> From: ffmpeg-user-bounces at ffmpeg.org [mailto:ffmpeg-user-
> bounces at ffmpeg.org] On Behalf Of Reindl Harald
> Sent: Tuesday, March 22, 2011 2:54 AM
> To: ffmpeg-user at ffmpeg.org
> Subject: Re: [FFmpeg-user] maximum CPU utilization with ffmpeg and
> libx264
> 
> 
> Am 22.03.2011 02:41, schrieb George D Pylant III:
> 
> > My understanding is that these cores support hyperthreading allowing
> > two threads to run simultaneously on each core.
> 
> yes and no
> since it is not a full core / cpu you can not expect wonders HT is
> using on non-ht-cpus wasted parts of the die (to say it simple)
> 
> > So why doesn't ffmpeg/libx264 use all "sixteen" cores, i.e. two
> > threads per core like handbrakecli does?  -
> 
> because you can not scale linear with more cpus and not every operation
> can benefit from multithreading
> 
> who tells you that the 100% cpu from "handbrakecli" is not wasted for
> useless thread-synchronisation, try it and reduce the software to use
> only 8 threads, maybe it gets slightly faster than with 16

You actually get more throughput with X264 if you turn on hyperthreading I ran some benchmark with and without it about a year and half ago on Nehalem based systems. There was up to 15% more throughput with hyper-threading on and using all core (hyper threaded or not). I wasn't actually looking at system load but just the average fps. Maybe these tests should be run again just to make sure that is still true.

> 
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> 
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