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    SubjectRe: [Bug #12465] KVM guests stalling on 2.6.28 (bisected)

    * Kevin Shanahan <kmshanah@ucwb.org.au> wrote:

    > > 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.
    >
    > It at least suggests a problem with interaction between the scheduler
    > and kvm, otherwise reverting that scheduler patch wouldn't have made the
    > regression go away.

    the scheduler affects almost everything, so almost by definition a
    scheduler change can tickle a race or other timing bug in just about any
    code - and reverting that change in the scheduler can make the bug go
    away. But yes, it could also be a genuine scheduler bug - that is always a
    possibility.

    Could you please run a cfs-debug-info.sh session on a CONFIG_SCHED_DEBUG=y
    and CONFIG_SCHEDSTATS=y kernel, while you are experiencing those
    latencies:

    http://people.redhat.com/mingo/cfs-scheduler/tools/cfs-debug-info.sh

    and post that (relatively large) somewhere, or send it as a reply after
    bzip2 -9 compressing it? It will include a lot of information about the
    delays your tasks are experiencing.

    Ingo


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