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    Subject[REGRESSION] High, likely incorrect process cpu usage counters with kvm and 2.6.2[67]
    Running an idle Windows VM on Linux 2.6.26+ with kvm, one sees high 
    values for the kvm process in top (30%-70% cpu), where one would
    normally expect 0%-1%. Surprisingly, the per-cpu system counters show
    almost 100% idle, leading me to believe this is an accounting error and
    that the process does not actually consume this much cpu.

    I bisected this to a scheduler change, namely

    commit 3e51f33fcc7f55e6df25d15b55ed10c8b4da84cd
    Author: Peter Zijlstra <>
    Date: Sat May 3 18:29:28 2008 +0200

    sched: add optional support for CONFIG_HAVE_UNSTABLE_SCHED_CLOCK

    this replaces the rq->clock stuff (and possibly cpu_clock()).

    - architectures that have an 'imperfect' hardware clock can set

    - the 'jiffie' window might be superfulous when we update tick_gtod
    before the __update_sched_clock() call in sched_clock_tick()

    - cpu_clock() might be implemented as:


    if the accuracy proves good enough - how far can TSC drift in a
    single jiffie when considering the filtering and idle hooks?

    [ various fixes and cleanups ]

    Signed-off-by: Peter Zijlstra <>
    Signed-off-by: Ingo Molnar <>

    Which is a bit too complex for me to work out.

    Further information:
    - the kvm thread which has the incorrect counter is the one that
    actually executes guest code
    - this thread mostly sleeps in schedule(), as one would expect
    - it is periodically woken up by a timer; perhaps the problem is that
    the process is sampled using the same timer, so it always shows as
    running (though I'd expect it to report 100% cpu in that case).

    Any help will be appreciated (or provided).

    error compiling committee.c: too many arguments to function

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      Last update: 2008-08-31 17:45    [W:0.030 / U:62.712 seconds]
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