linux-kernel - Re: [PATCH RFC V5 0/3] kvm: Improving directed yield in PLE handler

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Message-ID: <500D2162.8010209@redhat.com>
Date:	Mon, 23 Jul 2012 13:03:14 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
CC:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Ingo Molnar <mingo@...hat.com>, Rik van Riel <riel@...hat.com>,
	Srikar <srikar@...ux.vnet.ibm.com>,
	S390 <linux-s390@...r.kernel.org>,
	Carsten Otte <cotte@...ibm.com>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	KVM <kvm@...r.kernel.org>, chegu vinod <chegu_vinod@...com>,
	"Andrew M. Theurer" <habanero@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>, X86 <x86@...nel.org>,
	Gleb Natapov <gleb@...hat.com>, linux390@...ibm.com,
	Srivatsa Vaddagiri <srivatsa.vaddagiri@...il.com>,
	Joerg Roedel <joerg.roedel@....com>
Subject: Re: [PATCH RFC V5 0/3] kvm: Improving directed yield in PLE handler

On 07/18/2012 04:37 PM, Raghavendra K T wrote:
> Currently Pause Loop Exit (PLE) handler is doing directed yield to a
> random vcpu on pl-exit. We already have filtering while choosing
> the candidate to yield_to. This change adds more checks while choosing
> a candidate to yield_to.
> 
> On a large vcpu guests, there is a high probability of
> yielding to the same vcpu who had recently done a pause-loop exit. 
> Such a yield can lead to the vcpu spinning again.
> 
> The patchset keeps track of the pause loop exit and gives chance to a
> vcpu which has:
> 
>  (a) Not done pause loop exit at all (probably he is preempted lock-holder)
> 
>  (b) vcpu skipped in last iteration because it did pause loop exit, and
>  probably has become eligible now (next eligible lock holder)
> 
> This concept also helps in cpu relax interception cases which use same handler.
> 

Thanks, applied to 'queue'.


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


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