[linux-audio-user] Shaving CPU cycles

Paul Davis paul at linuxaudiosystems.com
Wed Jan 31 10:42:34 EST 2007


On Wed, 2007-01-31 at 13:46 +0200, Sampo Savolainen wrote:

> That might help a bit. But keep in mind that DSP usage of 80% is really
> high. It doesn't leave your computer much headroom for other tasks, or even
> plugins which might periodically use more CPU cycles than normally (=which
> is in fact a sign that a plugin is not "academically" real time safe). In my
> opinion 80% is about the maximum of DSP usage you can expect to be stable to
> work with.

indeed. when stephane, jesse and i were testing jack and jackdmp last
year for load limits, we found on linux and OS X that if the JACK DSP
figure got close to 80% it was very hard to ensure continued RT,
glitch-free performance. as sampo indicated, its partly a function of
code not being truly RT safe, and partly a function of the x86
architecture compared to a real DSP chip - the DSP is totally
deterministic in execution time, the x86 is not.





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