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Subject: Re: [patch] voluntary-preempt-2.6.9-rc1-bk4-Q5
From: Thomas Charbonnel <thomas@undata.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: Lee Revell <rlrevell@joe-job.com>, Daniel Schmitt <pnambic@unu.nu>,
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Ingo Molnar wrote :
> * Thomas Charbonnel <thomas@undata.org> wrote:
> 
> > As you can see ~1ms was probably an accident, and the latency does not
> > always come from do_timer. The constant is do_IRQ interrupting the
> > idle thread.
> 
> (do you have any sort of powersaving mode (ACPI/APM) enabled? If yes,
> could you try to tune it down as much as possible - disable any
> powersaving option in the BIOS and in the .config - kill apmd, etc.)
> 
> but i dont think it's powersaving - why would such an overhead show up
> in those functions. The only common thing seems to be that both
> mark_offset_tsc() and mask_and_ack_8259A() does port IO, which is slow -
> but still it shouldnt take ~0.5 msecs!
> 
> 	Ingo

Indeed, I just checked and my xrun every ~8 seconds problem is back. I
have acpi compiled in but acpi=off, but it doesn't seem to be honoured
(it was with 2.6.8.1, IIRC).

Thomas