On 8/25/2014 1:47 PM, Tal Maoz wrote:
When running just one instance of ffmpeg, it uses about 20-25% CPU. I then
continue to run a few more simultaneous
instances doing the exact same thing. When I have 4 instances, I see that
each instance is now using 30-35% CPU.
When I get to 7 instances, each one is using 40-45% CPU. Finally, when I
get to 9 instances, each instance uses 55-60% CPU!
As you will see below, my ffmpeg is compiled with vaapi support, but I've
already tried running with "-hwaccel none"
and with "-threads 1" and I still get the same results.
One would expect the CPU usage per instance to remain the same, right? am I
missing anything here?
well, not really.
how do you measure the cpu usage?
i mean you should consider with growing number of active processes a
significant increase in the process/thread switching overhead.
still, i think this shouldn't make such differences, but can't be
completely ignored.
additionally, by using the pipes, network, etc, i wonder if you don't
trigger any system I/O that piles up.
i'm not an expert but it wouldn't make sense for ffmpeg processes to be
somehow inter-dependent. and that's why i don't think this is an ffmpeg
issue, but you have to search for answers in the resources ffmpeg is using.
--
Claudiu
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