[x264-devel] Re: Scalability

[Christian Bienia]

Hi,

> For testing, change the #define X264_THREAD_MAX 16 (in common.h) to some
> bigger number. Then I'll see about dynamic allocation.

The performance doesn't improve significantly with more than 16 threads. Here's the results with a sufficiently high X264_THREAD_MAX value:

> #Threads      1     2     4     8    16   32    64
>  Time/[s]  2280  1265   662   345   200  202   201
> Speedup       1   1.8  3.45  6.61 11.39 11.3 11.35

#Threads      1     2     4     8    16   32    64
Time/[s]  2285  1267   662   344   200  172   172
Speedup       1   1.8  3.45  6.64 11.43 13.28 13.28

Looks like x264 can't use more than 13 CPUs effectively in practice (for
the used input and arguments).

You can drop me a note if you're interested in getting some test results
on a large-scale machine for an improved version of x264. I hope I'll
soon be able to contribute some improvements myself, but I'm pretty busy
at the moment.

Cheers,
Chris

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