linux-kernel - Re: [PATCH RFC 1/2] kvm vcpu: Note down pause loop exit

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Message-ID: <878vep4558.fsf@abhimanyu.in.ibm.com>
Date:	Thu, 12 Jul 2012 16:28:59 +0530
From:	Nikunj A Dadhania <nikunj@...ux.vnet.ibm.com>
To:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	Avi Kivity <avi@...hat.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Rik van Riel <riel@...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 1/2] kvm vcpu: Note down pause loop exit

On Wed, 11 Jul 2012 16:22:29 +0530, Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com> wrote:
> On 07/11/2012 02:23 PM, Avi Kivity wrote:
> >
> > This adds some tiny overhead to vcpu entry.  You could remove it by
> > using the vcpu->requests mechanism to clear the flag, since
> > vcpu->requests is already checked on every entry.
> 
> So IIUC,  let's have request bit for indicating PLE,
> 
> pause_interception() /handle_pause()
> {
>   make_request(PLE_REQUEST)
>   vcpu_on_spin()
> 
> }
> 
> check_eligibility()
>   {
>   !test_request(PLE_REQUEST) || ( test_request(PLE_REQUEST)  && 
> dy_eligible())
> .
> .
> }
> 
> vcpu_run()
> {
> 
> check_request(PLE_REQUEST)
>
I know check_request will clear PLE_REQUEST, but you just need a
clear_request here, right?


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