[PD] Realtime kernel

Jonathan Wilkes jancsika at yahoo.com
Sun Oct 2 22:36:48 CEST 2011


On the puredata.info FAQ at
there is this:

    Under Linux, with a recent version of the stable kernel (2.4.x), special low latency patches, some hard drive tuning, and ALSA drivers, average audio latencies is 1.5 ms. If you really load your system, a maximum audio latency of 3 ms can be reached. Pathological bad cases have been known to cause 8 ms latencies this seems like the upper bound. More information on low latency under Linux can be found at Benno's site on the subject.

TODO (tell the people that Pd has 3 blocks buffer, which gives you 4.5ms at least on 44.1kHz)

Can I get realtime priorities using the RT PREEMPT patch just using ALSA, and not JACK?

If I use JACK, does it make any difference whether or not I start Pd with the -rt flag 

(as long as I enable realtime in JACK, of course)?

What kind of hard drive tuning?  I've never read about that anywhere else.

What is the "pathological bad cases" refer to?

Benno's site only goes up to the 2.4 kernel.  Is there a more up-to-date source that we can link to from 

this FAQ?

More on the TODO?  If 4.5ms is the smallest latency at 44.1, what sample rate is being used to get the 

1.5ms average referred to in the paragraph above?

Any more info on the 3 block buffer?

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