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    SubjectRe: voluntary-preempt T3 latency spikes with fan speed change
    On Mon, 2004-10-11 at 13:03, Andrew Rodland wrote:
    > wrote:
    > >
    > > hi...
    > >
    > > i am seeing latency spikes (ie jack xruns) when the fan of my
    > > asus l3d laptop changes speed.
    > >
    > > is there any chance to fix this ?
    > > i have turned off acpi in the kernel, as this gives me latency spikes
    > > all over.
    > >
    > > i am quite new to the VP patches, and want to help where i can.
    > >
    > > i also got a quite strange latency trace here:
    > >
    > > could someone sched some light on this please ?
    > >
    > I can't say for certain, but I'm guessing that your laptop has a deeply
    > broken BIOS that implements ACPI and suchlike by using SMM, which blocks
    > out interrupts, and there's nothing, I believe, you can do about it.
    > Disabling ACPI seems sensible; at least you can avoid causing these delays
    > intentionally, but if some sensor interrupt triggers a flip into SMM to
    > enable the fan, you're just screwed for a number of milliseconds.

    Many, many people are seeing this problem (weird, often periodic latency
    spikes on laptops that go away when ACPI is disabled). This would
    explain a lot of weird bug reports. So are most laptops just
    incompatible with low latency applications, or are we talking about a
    small minority of broken hardware?

    Is there any way to tell a priori whether a machine will have this


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