From: Marcelo Tosatti <mtosatti@redhat.com>
To: Rik van Riel <riel@redhat.com>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
Avi Kivity <avi@redhat.com>, Srikar <srikar@linux.vnet.ibm.com>,
Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
"Nikunj A. Dadhania" <nikunj@linux.vnet.ibm.com>,
KVM <kvm@vger.kernel.org>, Ingo Molnar <mingo@redhat.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] kvm: handle last_boosted_vcpu = 0 case
Date: Fri, 6 Jul 2012 14:11:28 -0300 [thread overview]
Message-ID: <20120706171128.GA8835@amt.cnet> (raw)
In-Reply-To: <20120619165104.2a4574f8@annuminas.surriel.com>
On Tue, Jun 19, 2012 at 04:51:04PM -0400, Rik van Riel wrote:
> On Wed, 20 Jun 2012 01:50:50 +0530
> Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com> wrote:
>
> >
> > In ple handler code, last_boosted_vcpu (lbv) variable is
> > serving as reference point to start when we enter.
>
> > Also statistical analysis (below) is showing lbv is not very well
> > distributed with current approach.
>
> You are the second person to spot this bug today (yes, today).
>
> Due to time zones, the first person has not had a chance yet to
> test the patch below, which might fix the issue...
>
> Please let me know how it goes.
>
> ====8<====
>
> If last_boosted_vcpu == 0, then we fall through all test cases and
> may end up with all VCPUs pouncing on vcpu 0. With a large enough
> guest, this can result in enormous runqueue lock contention, which
> can prevent vcpu0 from running, leading to a livelock.
>
> Changing < to <= makes sure we properly handle that case.
>
> Signed-off-by: Rik van Riel <riel@redhat.com>
Applied, thanks.
prev parent reply other threads:[~2012-07-06 18:12 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-19 20:20 Regarding improving ple handler (vcpu_on_spin) Raghavendra K T
2012-06-19 20:51 ` [PATCH] kvm: handle last_boosted_vcpu = 0 case Rik van Riel
2012-06-20 20:12 ` Raghavendra K T
2012-06-21 2:11 ` Rik van Riel
2012-06-21 11:26 ` Raghavendra K T
2012-06-22 15:11 ` Andrew Jones
2012-06-22 21:00 ` Raghavendra K T
2012-06-23 18:34 ` Raghavendra K T
2012-06-27 20:27 ` Raghavendra K T
2012-06-27 20:29 ` [PATCH] kvm: handle last_boosted_vcpu = 0 case with benchmark detail attachment Raghavendra K T
2012-06-28 16:00 ` [PATCH] kvm: handle last_boosted_vcpu = 0 case Andrew Jones
2012-06-28 16:22 ` Raghavendra K T
2012-06-28 22:55 ` Vinod, Chegu
2012-06-28 22:55 ` Vinod, Chegu
2012-07-02 14:49 ` Rik van Riel
2012-07-03 3:30 ` Raghavendra K T
2012-07-05 14:45 ` Andrew Theurer
2012-06-21 6:43 ` Gleb Natapov
2012-06-21 10:23 ` Raghavendra K T
2012-06-28 2:14 ` Raghavendra K T
2012-07-06 17:11 ` Marcelo Tosatti [this message]
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