From: Rik van Riel <riel@redhat.com>
To: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
"H. Peter Anvin" <hpa@zytor.com>, Avi Kivity <avi@redhat.com>,
Ingo Molnar <mingo@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Srikar <srikar@linux.vnet.ibm.com>,
"Nikunj A. Dadhania" <nikunj@linux.vnet.ibm.com>,
KVM <kvm@vger.kernel.org>, Jiannan Ouyang <ouyang@cs.pitt.edu>,
chegu vinod <chegu_vinod@hp.com>,
"Andrew M. Theurer" <habanero@linux.vnet.ibm.com>,
LKML <linux-kernel@vger.kernel.org>,
Srivatsa Vaddagiri <srivatsa.vaddagiri@gmail.com>,
Gleb Natapov <gleb@redhat.com>
Subject: Re: [PATCH RFC 1/2] kvm: Handle undercommitted guest case in PLE handler
Date: Fri, 21 Sep 2012 09:02:03 -0400 [thread overview]
Message-ID: <505C654B.2050106@redhat.com> (raw)
In-Reply-To: <20120921120000.27611.71321.sendpatchset@codeblue>
On 09/21/2012 08:00 AM, Raghavendra K T wrote:
> From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
>
> When total number of VCPUs of system is less than or equal to physical CPUs,
> PLE exits become costly since each VCPU can have dedicated PCPU, and
> trying to find a target VCPU to yield_to just burns time in PLE handler.
>
> This patch reduces overhead, by simply doing a return in such scenarios by
> checking the length of current cpu runqueue.
I am not convinced this is the way to go.
The VCPU that is holding the lock, and is not releasing it,
probably got scheduled out. That implies that VCPU is on a
runqueue with at least one other task.
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1629,6 +1629,9 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
> int pass;
> int i;
>
> + if (unlikely(rq_nr_running() == 1))
> + return;
> +
> kvm_vcpu_set_in_spin_loop(me, true);
> /*
> * We boost the priority of a VCPU that is runnable but not
>
--
All rights reversed
next prev parent reply other threads:[~2012-09-21 13:02 UTC|newest]
Thread overview: 126+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-21 11:59 [PATCH RFC 0/2] kvm: Improving undercommit,overcommit scenarios in PLE handler Raghavendra K T
2012-09-21 12:00 ` [PATCH RFC 1/2] kvm: Handle undercommitted guest case " Raghavendra K T
2012-09-21 13:02 ` Rik van Riel [this message]
2012-09-21 17:24 ` Raghavendra K T
2012-09-24 15:41 ` Avi Kivity
2012-09-24 16:06 ` Avi Kivity
2012-09-24 16:14 ` Peter Zijlstra
2012-09-24 16:25 ` Avi Kivity
2012-09-25 8:09 ` Raghavendra K T
2012-09-25 8:54 ` Avi Kivity
2012-09-25 13:49 ` Raghavendra K T
2012-09-27 7:44 ` Gleb Natapov
2012-09-27 8:59 ` Avi Kivity
2012-09-27 9:11 ` Gleb Natapov
2012-09-27 9:33 ` Avi Kivity
2012-09-27 9:58 ` Gleb Natapov
2012-09-27 10:04 ` Avi Kivity
2012-09-27 10:08 ` Gleb Natapov
2012-09-27 10:15 ` Avi Kivity
[not found] ` <CAJocwcf+8u84_yDC-PK0Yni93YSTWzYvr69nq6b3pNv1MwVJzQ@mail.gmail.com>
2012-09-27 8:50 ` Avi Kivity
2012-09-27 11:26 ` Raghavendra K T
2012-09-27 12:06 ` Avi Kivity
2012-09-28 18:18 ` Konrad Rzeszutek Wilk
2012-09-30 8:16 ` Avi Kivity
[not found] ` <CAJocwcc19F+PtsQ5okGMvYeVnkEigpZRpwWY9JgeRPFqfcVoXA@mail.gmail.com>
2012-09-28 6:16 ` Raghavendra K T
2012-09-30 8:18 ` Avi Kivity
2012-09-30 11:07 ` Gleb Natapov
2012-09-30 11:13 ` Avi Kivity
2012-10-03 14:17 ` Raghavendra K T
2012-10-03 14:56 ` Avi Kivity
2012-10-04 7:29 ` Gleb Natapov
2012-10-05 8:36 ` Raghavendra K T
2012-10-07 9:51 ` Avi Kivity
2012-09-25 7:36 ` Raghavendra K T
2012-09-25 8:12 ` Avi Kivity
2012-09-25 14:21 ` Takuya Yoshikawa
2012-09-27 8:43 ` Avi Kivity
2012-10-03 12:22 ` Raghavendra K T
2012-10-03 17:05 ` Avi Kivity
2012-10-04 10:49 ` Raghavendra K T
2012-10-04 12:41 ` Avi Kivity
2012-10-04 13:07 ` Peter Zijlstra
2012-10-04 15:00 ` Avi Kivity
2012-10-09 18:51 ` Raghavendra K T
2012-10-10 2:59 ` Andrew Theurer
2012-10-10 17:54 ` Raghavendra K T
2012-10-10 18:03 ` David Ahern
2012-10-10 18:14 ` Raghavendra K T
2012-10-10 19:36 ` Andrew Theurer
2012-10-15 12:10 ` Raghavendra K T
2012-10-15 14:34 ` Andrew Theurer
2012-10-19 8:30 ` Raghavendra K T
2012-10-19 13:31 ` Andrew Theurer
2012-10-10 14:24 ` Andrew Theurer
2012-10-10 17:43 ` Raghavendra K T
2012-10-10 19:27 ` Andrew Theurer
2012-10-11 17:13 ` Raghavendra K T
2012-10-11 10:39 ` Nikunj A Dadhania
2012-10-18 12:39 ` Avi Kivity
2012-10-19 8:19 ` Raghavendra K T
2012-10-04 14:41 ` Andrew Theurer
2012-10-05 9:06 ` Raghavendra K T
2012-10-05 9:02 ` Raghavendra K T
2012-09-24 11:33 ` Peter Zijlstra
2012-09-24 11:40 ` Raghavendra K T
2012-09-21 12:00 ` [PATCH RFC 2/2] kvm: Be courteous to other VMs in overcommitted scenario " Raghavendra K T
2012-09-21 13:22 ` Rik van Riel
2012-09-21 13:46 ` Takuya Yoshikawa
2012-09-21 13:52 ` Rik van Riel
2012-09-21 17:45 ` Raghavendra K T
2012-09-24 13:43 ` Takuya Yoshikawa
2012-09-24 15:26 ` Avi Kivity
2012-09-24 15:34 ` Peter Zijlstra
2012-09-24 15:43 ` Avi Kivity
2012-09-24 15:52 ` Peter Zijlstra
2012-09-24 15:58 ` Avi Kivity
2012-09-24 16:05 ` Peter Zijlstra
2012-09-24 16:10 ` Avi Kivity
2012-09-24 16:13 ` Peter Zijlstra
2012-09-24 16:21 ` Avi Kivity
2012-09-25 10:11 ` Avi Kivity
2012-09-21 13:18 ` [PATCH RFC 0/2] kvm: Improving undercommit,overcommit scenarios " Chegu Vinod
2012-09-21 17:36 ` Raghavendra K T
2012-09-24 8:42 ` Dor Laor
2012-09-24 12:02 ` Raghavendra K T
2012-09-25 15:00 ` Dor Laor
2012-09-26 12:27 ` Konrad Rzeszutek Wilk
2012-09-27 10:07 ` Raghavendra K T
2012-09-27 9:49 ` Raghavendra K T
2012-09-27 10:28 ` Andrew Jones
2012-09-27 10:44 ` Avi Kivity
2012-09-27 11:31 ` Raghavendra K T
2012-09-27 10:33 ` Dor Laor
2012-09-24 11:34 ` Peter Zijlstra
2012-09-24 11:52 ` Raghavendra K T
2012-09-24 12:36 ` Peter Zijlstra
2012-09-24 13:29 ` Raghavendra K T
2012-09-24 13:54 ` Peter Zijlstra
2012-09-24 14:16 ` Raghavendra K T
2012-09-25 13:40 ` Raghavendra K T
2012-09-27 8:36 ` Avi Kivity
2012-09-27 11:23 ` Raghavendra K T
2012-09-27 12:03 ` Avi Kivity
2012-09-27 12:25 ` Andrew Theurer
2012-09-28 5:38 ` Raghavendra K T
2012-09-28 5:45 ` H. Peter Anvin
2012-09-28 6:03 ` Raghavendra K T
2012-09-28 8:38 ` Peter Zijlstra
2012-09-28 11:40 ` Andrew Theurer
2012-09-28 14:11 ` Raghavendra K T
2012-09-28 14:13 ` Peter Zijlstra
2012-09-30 8:24 ` Avi Kivity
2012-10-03 14:29 ` Raghavendra K T
2012-10-03 17:25 ` Avi Kivity
2012-10-04 10:56 ` Raghavendra K T
2012-10-04 12:44 ` Avi Kivity
2012-10-05 9:04 ` Raghavendra K T
2012-09-24 15:51 ` Avi Kivity
2012-09-24 16:03 ` Peter Zijlstra
2012-09-24 16:20 ` Avi Kivity
2012-09-26 13:20 ` Andrew Jones
2012-09-26 13:26 ` Peter Zijlstra
2012-09-26 13:39 ` Andrew Jones
2012-09-26 13:45 ` Peter Zijlstra
2012-09-26 12:57 ` Andrew Jones
2012-09-27 10:21 ` Raghavendra K T
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