From: Paolo Bonzini <pbonzini@redhat.com>
To: Alex Bligh <alex@alex.org.uk>
Cc: Luigi Rizzo <rizzo@iet.unipi.it>, qemu-devel <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] commit b1bbfe72 causes huge slowdown with no kvm
Date: Wed, 20 Nov 2013 14:55:08 +0100 [thread overview]
Message-ID: <528CBF3C.7060004@redhat.com> (raw)
In-Reply-To: <D98FD4F5-B7C2-4596-A604-0CFB652F764D@alex.org.uk>
Il 20/11/2013 14:47, Alex Bligh ha scritto:
> I think you are saying this sounds like another underlying bug
> (no pause instruction) uncovered by the timer patches rather than
> a bug in the timer patches.
>
> Reading
> http://software.intel.com/file/27087
> perhaps the answer is for pause to yield the lock.
>
> However, what if an arbitrary guest foolishly /does/ do a tight
> spinlock without calling pause?
It would be a problem. I don't think it has to be fixed though (and
anyway of course not now).
The fix could be to make TCG use "real" SMP instead of round-robin.
Paolo
prev parent reply other threads:[~2013-11-20 13:55 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-19 23:00 [Qemu-devel] commit b1bbfe72 causes huge slowdown with no kvm Luigi Rizzo
2013-11-20 9:41 ` Paolo Bonzini
2013-11-20 11:00 ` Luigi Rizzo
2013-11-20 11:19 ` Paolo Bonzini
2013-11-20 13:47 ` Alex Bligh
2013-11-20 13:55 ` Paolo Bonzini [this message]
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