DVD Playback and Hyperthreading

Bob Chiodini chiodr at kscems.ksc.nasa.gov
Wed May 12 14:35:27 UTC 2004


I was asked to troubleshoot a Xine DVD playback problem on a Dell
Inspiron 9100 (P4 3.2 GHz, HT-enabled).  DVD playback was
"herky-jerky".  

I found that killing irqbalance or booting without ACPI=on seems to
correct the playback.  Watching /proc/interrupts (with ACPI=on and
irqbalance running) indicates that each time the playback paused CPU1
handled the interrupts for the DVD's IDE controller.  When playback was
smooth CPU0 was fielding the IDE interrupts.  Furthermore, xine was
running on CPU0.  Without the ACPI=on cmdline parameter all of the
interrupts were handled by CPU0.  The laptop is running the latest FC1
kernel.

Questions:

Is there a way to associate a specific program (e.g. xine) with a
specific processor and also associate a device's interrupt with a
specific processor, without killing irqbalance or disabling ACPI?

Does disabling irqbalance cause any significant problems?  Performance,
or otherwise.

Is this likely a problem with a 2.6.x kernel?  I do not have an
HT-capable FC2 machine handy.

Bob...
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