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    SubjectRe: [Bug #12465] KVM guests stalling on 2.6.28 (bisected)
    Ingo Molnar wrote:
    > * Kevin Shanahan <kmshanah@ucwb.org.au> wrote:
    >
    >
    >> On Mon, 2009-01-19 at 22:45 +0100, Rafael J. Wysocki wrote:
    >>
    >>> This message has been generated automatically as a part of a report
    >>> of regressions introduced between 2.6.27 and 2.6.28.
    >>>
    >>> The following bug entry is on the current list of known regressions
    >>> introduced between 2.6.27 and 2.6.28. Please verify if it still should
    >>> be listed and let me know (either way).
    >>>
    >>>
    >>> Bug-Entry : http://bugzilla.kernel.org/show_bug.cgi?id=12465
    >>> Subject : KVM guests stalling on 2.6.28 (bisected)
    >>> Submitter : Kevin Shanahan <kmshanah@ucwb.org.au>
    >>> Date : 2009-01-17 03:37 (3 days old)
    >>>
    >> Yes, please keep this on the list.
    >>
    >
    > This only seems to occur under KVM, right? I.e. you tested it with -no-kvm
    > and the problem went away, correct?
    >
    > This suggests some sort of KVM-specific problem. Scheduler latencies in
    > the seconds that occur under normal load situations are noticed and
    > reported quickly - and there are no such open regressions currently.
    >
    >

    Not necessarily. -no-kvm runs with only one thread, compared to kvm
    that runs with 1 + nr_cpus threads.

    > Avi, can you reproduce these latencies?

    No.

    > A possibly theory would be some
    > sort of guest wakeup problem/race triggered by a shift in
    > preemption/scheduling patterns. Or something related to preempt-notifiers
    > (which KVM is using). A genuine scheduler bug is in the cards too, but the
    > KVM-only angle of this bug gives it a low probability.
    >

    Can we trace task wakeups somehow? (latency between wakeup and actually
    running).

    --
    error compiling committee.c: too many arguments to function



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