From mboxrd@z Thu Jan  1 00:00:00 1970
From: Rik van Riel <riel@redhat.com>
Subject: Re: Preemptable Ticket Spinlock
Date: Mon, 22 Apr 2013 16:50:38 -0400
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Cc: Jiannan Ouyang <ouyang@cs.pitt.edu>,
	LKML <linux-kernel@vger.kernel.org>,
	Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
	Avi Kivity <avi.kivity@gmail.com>,
	Gleb Natapov <gleb@redhat.com>, Ingo Molnar <mingo@redhat.com>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	Srikar <srikar@linux.vnet.ibm.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"Nikunj A. Dadhania" <nikunj@linux.vnet.ibm.com>,
	KVM <kvm@vger.kernel.org>, Thomas Gleixner <tglx@linutronix.de>,
	Chegu Vinod <chegu_vinod@hp.com>,
	"Andrew M. Theurer" <habanero@linux.vnet.ibm.com>,
	Srivatsa Vaddagiri <srivatsa.vaddagiri@gmail.com>,
	Andrew Jones <drjones@redhat.com>,
	Karen Noel <knoel@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
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On 04/22/2013 04:48 PM, Peter Zijlstra wrote:

> Hmm.. it looked like under light overcommit the paravirt ticket lock
> still had some gain (~10%) and of course it brings the fairness thing
> which is always good.
>
> I can only imagine the mess unfair + vcpu preemption can bring to guest
> tasks.

If you think unfairness + vcpu preemption is bad, you haven't
tried full fairness + vcpu preemption :)

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