linux-kernel - Re: [PATCH RFC V2 2/2] kvm PLE handler: Choose better candidate for directed yield

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Message-ID: <4FFC853B.30900@redhat.com>
Date:	Tue, 10 Jul 2012 15:40:43 -0400
From:	Rik van Riel <riel@...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>, Avi Kivity <avi@...hat.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 V2 2/2] kvm PLE handler: Choose better candidate for
 directed yield

On 07/10/2012 03:31 PM, Raghavendra K T wrote:
> From: Raghavendra K T<raghavendra.kt@...ux.vnet.ibm.com>
>
> Currently PLE handler can repeatedly do a directed yield to same vcpu
> that has recently done PL exit. This can degrade the performance.
>
> Try to yield to most eligible guy instead by alternate yielding.
> Precisely, give chance to a VCPU which has:
>   (a) Not done PLE exit at all (probably he is preempted lock-holder)
>   (b) VCPU skipped in last iteration because it did PL exit, and probably
>   has become eligible now (next eligible lock holder)
>
> Signed-off-by: Raghavendra K T<raghavendra.kt@...ux.vnet.ibm.com>

Reviewed-by: Rik van Riel <riel@...hat.com>

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