[mythtv-users] ffmpeg and multiple CPUs. Was: Should I be switching to 0.21?

[John Drescher]

>  >  However...and this is the interesting part...if I use ffmpeg but
>  >  switch the number of CPUs to 1 instead of 2 the performance of the two
>  >  is virtually identical.  It seems that, at least with my
>  >  hyper-threaded 3 Ghz P4, ffmpeg works much better with a single core.
>  >
You do realize hyperthereading can have a negative impact on
performance? I mean a single core P4 with hyperthreading may look like
two cores but it certianly is not. Hyperthreading works only because
the P4 had such a long pipeline that stalls occurred so frequently
(mispredicted branch ...) and in this case a second thread could be
executed where no ops would be inserted in the pipeline.

John