Re: [Bug #12465] KVM guests stalling on 2.6.28 (bisected)
From: Avi Kivity
Date: Tue Jan 20 2009 - 07:38:35 EST
Ingo Molnar wrote:
* Kevin Shanahan <kmshanah@xxxxxxxxxxx> 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@xxxxxxxxxxx>
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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