[x265] Question about CPU addressing (more than 64 logical CPUs)

[Michael Lackner]

Hello,

I've looked through the x265 documentation, and found this for the "-pools" option:

"In the case that any threadpool has more than 64 threads, the threadpool may be broken
down into multiple pools of 64 threads each;"

But that's NUMA-related.

Now here's the question: How will x265 behave on systems with a flat addressing model (no
libnuma), but more than 64 logical CPUs? Currently, modern operating system kernels seem
to have gotten their address bit vectors bumped up from 64 to 256 bits, so users can
address up to 256 CPUs either without NUMA entirely, or within a single NUMA threadpool.

Say I have a UNIX machine without NUMA, but with 128 or 256 logical CPUs. How will x265
behave on such a system? Will it be able to spawn more than 64 threads per process, or not?

Where I to launch multiple processes of 64 threads each, would the kernel be able to push
the threads to free CPUs, or does x265 "lock on" to the first 64 forcefully (not sure if
this is even possible, just asking)?

Thank you for the clarification!

-- 
Michael Lackner
Lehrstuhl für Informationstechnologie (CiT)
Montanuniversität Leoben
Tel.: +43 3842 402 1505 | Mail: michael.lackner at unileoben.ac.at
Fax.: +43 3842 402 1502 | Web: http://institute.unileoben.ac.at/infotech