linux-kernel - Re: [PATCH RFC 2/2] kvm: Be courteous to other VMs in overcommitted scenario in PLE handler

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Message-ID: <1348500861.11847.72.camel@twins>
Date:	Mon, 24 Sep 2012 17:34:21 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Avi Kivity <avi@...hat.com>
Cc:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Ingo Molnar <mingo@...hat.com>, Rik van Riel <riel@...hat.com>,
	Srikar <srikar@...ux.vnet.ibm.com>,
	"Nikunj A. Dadhania" <nikunj@...ux.vnet.ibm.com>,
	KVM <kvm@...r.kernel.org>, Jiannan Ouyang <ouyang@...pitt.edu>,
	chegu vinod <chegu_vinod@...com>,
	"Andrew M. Theurer" <habanero@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Srivatsa Vaddagiri <srivatsa.vaddagiri@...il.com>,
	Gleb Natapov <gleb@...hat.com>
Subject: Re: [PATCH RFC 2/2] kvm: Be courteous to other VMs in overcommitted
 scenario in PLE handler

On Mon, 2012-09-24 at 17:26 +0200, Avi Kivity wrote:
> I think this is a no-op these (CFS) days.  To get schedule() to do
> anything, you need to wake up a task, or let time pass, or block.
> Otherwise it will see that nothing has changed and as far as it's
> concerned you're still the best task to be running (otherwise it
> wouldn't have picked you in the first place). 

Time could have passed enough before calling this that there's now a
different/more eligible task around to schedule.

Esp. for a !PREEMPT kernel this is could be significant.
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