linux-kernel - Re: [PATCH RFC V4 3/3] kvm: Choose better candidate for directed yield

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Date:	Mon, 16 Jul 2012 12:10:27 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Avi Kivity <avi@...hat.com>
CC:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Marcelo Tosatti <mtosatti@...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 V4 3/3] kvm: Choose better candidate for directed
 yield

On 07/16/2012 06:07 AM, Avi Kivity wrote:

>> +{
>> +	bool eligible;
>> +
>> +	eligible = !vcpu->ple.cpu_relax_intercepted ||
>> +			(vcpu->ple.cpu_relax_intercepted&&
>> +			 vcpu->ple.dy_eligible);
>> +
>> +	if (vcpu->ple.cpu_relax_intercepted)
>> +		vcpu->ple.dy_eligible = !vcpu->ple.dy_eligible;
>
> Probably should assign 'true', since the previous value is essentially
> random.

I suspect the intended purpose of this conditional is to
flip the eligibility of a vcpu for being selected as a
direct yield target.

In other words, that bit of the code is correct.

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