Number of threads DoM can use

[gunnar]

I was wondering about this settings.
I know it says threads but is better to select the number of cores the CPU have rather than thread?

For example, my CPU have 12 cores but 24 threads.
So should i set this settings in DoM as the number of cores the CPU have or threads?

[Carsten]

To the number of logical cores, which is twice the number of physical cores for HT machines. In your case, 24. DCP-o-matic will also set this as default setting (it will detect the available number of logical cores and set accordingly). Normally, there is no need to change this from the default value.

- Carsten

[Collison]

Hi Carsten, does DCP-o-matic have a cap on how many cores it can utilize?

[carl]

There's no explicit cap but there will be diminishing returns as the number of cores goes up.

[Carsten]

I have tried like 60 or 80 on systems with actual 24, and there wasn't a real issue yet. Keep in mind, however, that every thread consumes it's own share of memory - and if that brings your system into swapping, it more or less comes to a halt encoding wise. That becomes more critical if you work in 4k.

It doesn't make sense to set more threads than actual logical cores are available. Also, the system becomes very sluggish.

Typically, when you install DCP-o-matic and start it for the first time, DCP-o-matic will detect the actual number of cores and sets a useful value. It may be necessary to adjust it when you later migrate the installation/config to a system with more cores, or if you add remote encoding servers. Before DCP-o-matic 2.7.4, it paid out a bit to tweak that value, as the code lacked some optimizations. Since 2.7.4 or so, matching the setting with the actual number of cores is the best you can get.

If you look into a project log, DCP-o-matic will show the CPU type/count and number of logical cores it has detected.


- Carsten