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From: Avi Kivity <avi@redhat.com>
To: Takuya Yoshikawa <takuya.yoshikawa@gmail.com>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
	Rik van Riel <riel@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	"H. Peter Anvin" <hpa@zytor.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: Thu, 27 Sep 2012 10:43:01 +0200	[thread overview]
Message-ID: <50641195.5040208@redhat.com> (raw)
In-Reply-To: <20120925232122.e6fabbc5c472148aeec70234@gmail.com>

On 09/25/2012 04:21 PM, Takuya Yoshikawa wrote:
> On Tue, 25 Sep 2012 10:12:49 +0200
> Avi Kivity <avi@redhat.com> wrote:
> 
>> It will.  The tradeoff is between false-positive costs (undercommit) and
>> true positive costs (overcommit).  I think undercommit should perform
>> well no matter what.
>> 
>> If we utilize preempt notifiers to track overcommit dynamically, then we
>> can vary the spin time dynamically.  Keep it long initially, as we get
>> more preempted vcpus make it shorter.
> 
> What will happen if we pin each vcpu thread to some core?
> I don't want to see so many vcpu threads moving around without
> being pinned at all.

If you do that you've removed a lot of flexibility from the scheduler,
so overcommit becomes even less likely to work well (a trivial example
is pinning two vcpus from the same vm to the same core -- it's so
obviously bad no one considers doing it).

> In that case, we don't want to make KVM do any work of searching
> a vcpu thread to yield to.

Why not?  If a vcpu thread on another core has been preempted, and is
the lock holder, and we can boost it, then we've fixed our problem.
Even if the spinning thread keeps spinning because it is the only task
eligible to run on its core.

-- 
error compiling committee.c: too many arguments to function

  reply	other threads:[~2012-09-27  8:43 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
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 [this message]
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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