How To Enable Use Of Logical Cpus On Atom 230/330

[Radek]

it should run a bit better when utilizing two logical threads (or 4 on 330) on Atom. I can say that as my experiments running multiple instance of tasks (few concurrent running lame encoders for example) they show significant improvements. After all multithreading helps to avoid pipeline stalls, which are costly in “in order” architecture like Atom.

As it’s now Renoise detects number of logical cores properly by limits itself just to one. From logs:
“Renoise LOG> CPU: Found 1 enabled unit(s) with 1 core(s) / 2 logical processor(s) per unit. 1 cores are enabled in total.”

Why it’s so? Isn’t it an artefact of Pentium4 rather problematic “hyperthreading”? On Atoms not using it is rather wasteful imho. If there aren’t any special reason to disable support for logical threads then enabled them please.
I’m using Ubuntu 9.04 btw.

[benJam]

from the renoise faq:

Renoise 1.9 supports now multicore CPUs.
Here is what you can expect from it and what not:
Hyperthreading CPUs are not supported.
They will be treated like single CPUs as our testing results did not show any real performance gains, or even worse: They cause a performance decrease.

Why? HT Cpus are “faked” multicore CPUs. Realtime parallel Audio processing (the way we use the multiple cores) can not really be handled by them.

[Radek]

@benJam

from the renoise faq:

Well… it should be the user thing to deicide, shouldn’t it?
It’s proven that modern multithreading processors like i7 and Atoms can benefit enormously running multiple threads. That “CPU faking” helps to alleviate pipeline stalls (even Atom is dual issue superscalar CPU). Of course it depends on an application but I’m surprised there isn’t any “force” option anyway.

[It-Alien]

that FAQ is related to the tests which have been made on the HyperThreading technology. I don’t think that Atom CPU’s behave the same.

actually, we never tried Renoise with an Atom CPU. Maybe we should users try this on next beta cycle.