[PD] how to optimize system for pd performance?

Roman Haefeli reduzierer at yahoo.de
Sun Dec 7 16:58:55 CET 2008


hi all

i encountered, that 'ondemand' cpu scaling doesn't work correctly when
running pd with realtime priority. even if pd is using 80% or more
resources (of one core), the cpu frequency is not raised and staying at
800MHz. i can force it to go up by running an instance of 'burnMMX' (or
something else, that burns as many cycles as possible). when running pd
with '-nrt', automatic scaling works fine. also, as a workaround, i can
set the scaling_governor to 'userspace' and then set the cpu frequency
manually. 

could it be, that when pd is running in realtime mode, its priority is
higher then the one of the process, that controls the cpu frequency, so
that cpu time is assigned rather to pd and only at times, when pd is not
using it, the governor can adjust the frequency (which would be the
loweset, since pd is not using much cpu at that time)?

i wonder, what other people do in a performative situation? do you
simply turn automatic scaling off and set frequency to the highest
value? or is it only me having this issue?


while we are at priorities:
i figured out, that all four combinatios are possible:
pd -rt, jackd -R
pd -nrt, jackd -R
pd -rt, jackd
pd -nrt, jackd

i guess, that the first one should be used for best performance, right?
but how to set priorities between jackd and pd? can this be fine-tuned
at all (i know you can fine-tune jackd) ? if so, which should have
higher priority? 

roman




		
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