Re: Audio threads scheduling
Re: Audio threads scheduling
- Subject: Re: Audio threads scheduling
- From: Stéphane Letz <email@hidden>
- Date: Fri, 2 Apr 2004 11:47:42 +0200
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Message: 7
From: Jeff Moore <email@hidden>
Subject: Re: Audio threads scheduling
Date: Thu, 1 Apr 2004 15:43:52 -0800
To: CoreAudio API <email@hidden>
You have a point about MillionMonkeys. It is a good example of the
priority inversion I was talking about in my other messages and why the
HAL does things a little differently with it's IO threads.
Yes.
I tested using 2 copies of the program, one running a thread with a
buffer size of 64, the other with a buffer size of 1024, both using a
real-time feeder thread. Indeed the thread with buffer size of 64 can
not meet it's dealdine. Now if I correct the setThreadToPriority
function to allocate values for the computation period the way you
described it for the IO thread, then things start to work.
Actually how are *computed* these values for the computation value? Are
then coming from a theoritical framework?
I saw also that the Midi IOThread (that call a RedadpProc callback) has
the following values:
period : 0 (no periodicity)
computation : 250 us
constraint : 500 us
preemptable = 1
I guess these value are carefully choosen to be compatible the values
taken for the Audio IO thread?
I wouldn't stress to hard over it. MillionMonkeys was originally
written to help stress out the system, all the while trying to simulate
the different strategies a real world audio engine might use for it's
threading. One of the lessons we learned from it is that having your
feeder threads be real-time isn't normally a good thing.
Buy why?
Actually using fixed priority 63 for the feeder threads does not work
so well...
And using real-time 96 for the feeder threads with properly choosen
values for the computation parameter work quite well and solve
interleaving problems.
So what are the *technical* issues to prevent using real-time feeder
threads?
Thanks
Stephane Letz
On Apr 1, 2004, at 3:20 PM, Stiphane LETZ wrote:
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