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    SubjectRe: Interrupt latency on some 945GM platforms
    On Tue, 14 Sep 2010, Vasily Khoruzhick wrote:

    > В сообщении от 14 of September 2010 03:55:32 автор Venkatesh Pallipadi
    > написал:
    >
    > > Whats the clockevent in this case ("Tick Device" section of
    > > /proc/timer_list). clocksource= option only changes the clocksource used
    > > to maintain
    > > timeofday. But, timer interrupt (clockevent) source will not change.
    > > Wondering how just the clocksource change is making the diff here..
    > >
    > > Also, if clocksource tsc has a higher rating than HPET. The reason
    > > HPET is getting used as clocksource in the first place seems to be due
    > > to TSC is not a dependable clocksource on this platform (may be it
    > > stops in C3). So, I am not sure forcing it to tsc will be a good
    > > thing. May be clocksource=acpi_pm is a better thing to try.
    > >
    > > Thanks,
    > > Venki
    >
    > I investigated it a bit and found out that single nohz=off option helps. Just
    > changing clocksource doesn't help, but it works smoothly with any clocksource
    > with nohz=off. So, it seems that something wrong with intel driver while
    > system is in tickless mode.

    Can you try with NOHZ enabled and the following on the kernel command line:

    processor.max_cstate=1

    Make sure that CONFIG_ACPI_PROCESSOR is set to "y" and not to "m"

    If that works, then try

    processor.max_cstate=2

    Thanks,

    tglx
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