Re: Using getrusage function in a CoreAudio callback
Re: Using getrusage function in a CoreAudio callback
- Subject: Re: Using getrusage function in a CoreAudio callback
- From: Jeff Moore <email@hidden>
- Date: Wed, 26 Mar 2003 11:23:01 -0800
I don't know too much about getrusage or how it's implemented. From
reading the man page, I would guess that it does sysctl or ioctl call
or possibly uses a mach message, probably including waiting for a
reply, directly. All these mechanisms involve system locks and other
things that can block. So, I would expect that calling getrusage from
inside an IOProc would interfere with the timing.
When I do profiling of the IO thread, I just use the host time clock as
follows:
OSStatus MyIOProc(...)
{
UInt64 theStartTime = AudioGetCurrentHostTime();
do the work;
UInt64 theEndTime = AudioGetCurrentHostTime();
log the performance metrics to a safe place so another thread can
write them out;
}
On Wednesday, March 26, 2003, at 10:00 AM, Stephane Letz wrote:
Hi,
I'm using the "getrusage" function to measure CPU use in a CoreAudio
callback. With very small buffer sizes for the CoreAudio callback, the
getrusage call cause gliches as if the getrusage itself was too time
consuming or cause something weird in the kernel.
is this the case? Is there any other way to measure CPU use in this
case?
Thanks
Stephane Letz
Grame: Centre National de creation musicale
9, Rue du Garet
69001 Lyon
Tel: 04-72-07-37-00
Fax: 04-72-07-37-01
Web: www.grame.fr
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--
Jeff Moore
Core Audio
Apple
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