High CPU Usage w/ACPI enabled="true"

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High CPU Usage w/ACPI enabled="true"

H: Win7 64bit / 4GB / Q9550 / Dell Vostro 420
G: Ubuntu 32 & 64 / 9.x-10.04

(Processors set to '4')

I've had consistent high cpu usage problems for as long as i can remember
with multiple+ versions of virtualbox dating back to last year.

It seems every time i'm drawn back to this acpi setting.

By 'high cpu usage' i mean, ridiculous. The guest OS fresh installed 32/64 or
running Live will idle using 40-80-90%+ cpu bouncing all over the place.

The Sluggishness borders on immediately noticeable - just booting an install
or booting up live/install (via iso)

Today i spent a few hours with a fresh installed 10.04 32bit, live 64bit
& installed 64bit and it seems (again) that changing:

ACPI enabled="true"

to

ACPI enabled="false"

in the machines XML file fixes the high cpu usage/sluggishness problem.

- I've noticed VirtualBox sometimes flips this back to 'True'
- It may require restarting or shutting down VirtualBox for it to stick.

So that's the run down. Some side notes involve IO-APIC.

Assuming ACPI enabled="true" :

If IO APIC is ON @ 4 CPU -> High CPU/Sluggishness (40-80-90%+ @ Idle)

If IO APIC is OFF @ 1 CPU -> Normal CPU/Speed. / The performance is *much much* faster than IO APIC ON @ 4 CPU

IF IO APIC is ON @ 1 CPU -> CPU Usage Seems Excessive. 15-20% Idle. Speed is Slower.
This might be considered normal given the known impact?

Assuming ACPI enabled="false" - All IO APIC + CPU settings seem to act normally?

More Side notes:

Sometimes (with ACPI OFF) while booting 64bit Live/ISO:

'Kernel panic - not syncing: IO-APIC + timer doesn't work! boot with apic=debug and send a report.
Then try booting with the 'noapic' option

- Restarting virtualbox the error goes away

More Side notes:

Every so often i'll get away with booting live & installing with no cpu usage/sluggishness
problems (while 'true) at all. But consistently about a day & a re-boot of the host later it comes back & disabling
acpi fixes it.

So yes, every so often everything runs fine straight on through. But in the end it's just a ticking time bomb.

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This is the panic that occurs every so often but then is fine on the next restart.

Currently 3.2.0_BETA3 r61544