Re: Pinning IO Thread to a particular processor
Re: Pinning IO Thread to a particular processor
- Subject: Re: Pinning IO Thread to a particular processor
- From: email@hidden (Stefan Haller)
- Date: Wed, 1 Feb 2006 18:46:30 +0100
- Organization: Ableton
Jeff Moore <email@hidden> wrote:
> On Jan 30, 2006, at 11:02 AM, Stefan Haller wrote:
>
> > We are observing that on a Quad G5 we get glitches or dropouts when we
> > lower the buffer size under high audio load (of course); but with all
> > four cores enabled, we get these glitches far earlier (with a higher
> > buffer size) than with only one core enabled.
>
> What buffer size and sample rate are you seeing the problems?
We did another test today with 44kHz sample rate and a buffer size of
128 frames. Audio load was around 70%, as displayed in Live's CPU
meter. When turning on only one CPU, the sound was perfect; when
turning on any number of CPUs > 1 (no matter which ones), there was not
only glitches, but continuous crackle. It didn't matter which CPUs we
turned on (e.g. 1+2 or 1+3, or all four), which leads me to believe it's
not a cache issue.
> You'll have to tell us. You can use HALLab's IO cycle telemetry
> window to track what the IO thread is doing. If you run it as root,
> you can also take kernel traces under a variety of circumstances
> based on the telemetry.
I'm afraid I need help with interpreting the data.
With 1 CPU, we get occasional overloads (pretty infrequent); here's a
screenshot of one:
<http://home.snafu.de/stk/tmp/1_CPU.png>
With 4 CPUs we get very frequent red entries in the telemetry window;
here's one:
<http://home.snafu.de/stk/tmp/4_CPUs.png>
Now what does this tell me?
Also, we turned on the "Latency trace on overload" checkbox, and the
console said it did take a trace, but it didn't mention where it was
written to; I didn't manage to find it.
--
Stefan Haller
Ableton
http://www.ableton.com/
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