[x265] >64 maximum threads per NUMA node and per system for flat topologies

[Mario *LigH* Rohkrämer]

Disclaimer: I am not a specialist here, just a brief reply...

Obviously, multithreading requires support from the CPU hardware and 
from the operating system. As long as they are limited (core mask 
register width, API parameter width), an application won't be able to 
break these limits.

But there is also a limit of efficiency. Running the encoding in 
parallel on more cores may speed up the calculation but also may reduce 
the scope of every task; finding redundancies in the material to be used 
for bitrate reduction may get harder when each thread sees less of the 
material due to some separation.

Furthermore, parallelism saturates. The effort of managing parallel 
threads and the amount of stalling due to dependencies probably makes 
one encoding task with the maximum number of threads less efficient than 
running two tasks with each half of that.

So, whether you can is just half the question... But you are probably 
most interested in the first of my three remarks for now. That much, I 
will be curious too.

-- 

Fun and success!

Mario *LigH* Rohkrämer
maito:contact at ligh.de