[FFmpeg-devel] [PATCH] libsvtav1: Add logical_processors option

Mark Thompson sw at jkqxz.net
Wed Feb 17 23:43:47 EET 2021


On 17/02/2021 18:58, Christopher Degawa wrote:
> On Sun, Feb 14, 2021 at 12:27 PM Christopher Degawa <ccom at randomderp.com>
> wrote:
> 
>> That said, if you have a general use-case where this is helpful and the
>>> documentation explains what it is doing (and warns about the bad cases)
>>> then maybe?
>>>
>>
>> The main use case we have internally is to able to run multiple instances
>> of SvtAv1EncApp with `--lp 1` without worrying about potentially choking
>> out all of them and also for testing for potential single versus multi-core
>> issues. Also, it seems my wording was wrong and it's not to "certain CPUs",
>> but to a "certain number of CPUs"
>>
> 
> Another usage for this option would be to limit the amount of memory used
> as right now the ram usage is tied to the numbers of cores used.

So what does it actually do, then?

I just tried running with it here and all of my threads get default affinity, so whatever it is actually doing it seems like it is nothing to do with logical processors.

It changes the thread count slightly but still makes lots of threads.  It does seem like the number correlates somehow with how much CPU it uses, but it's not an upper bound.

- Mark


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