linux-kernel - Re: [PATCH RFC 1/2] kvm: Handle undercommitted guest case in PLE handler

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Message-ID: <506DA48C.8050200@redhat.com>
Date:	Thu, 04 Oct 2012 17:00:28 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	Rik van Riel <riel@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	Marcelo Tosatti <mtosatti@...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 1/2] kvm: Handle undercommitted guest case in PLE
 handler

On 10/04/2012 03:07 PM, Peter Zijlstra wrote:
> On Thu, 2012-10-04 at 14:41 +0200, Avi Kivity wrote:
>> 
>> Again the numbers are ridiculously high for arch_local_irq_restore.
>> Maybe there's a bad perf/kvm interaction when we're injecting an
>> interrupt, I can't believe we're spending 84% of the time running the
>> popf instruction. 
> 
> Smells like a software fallback that doesn't do NMI, hrtimer based
> sampling typically hits popf where we re-enable interrupts.

Good nose, that's probably it.  Raghavendra, can you ensure that the PMU
is properly exposed?  'dmesg' in the guest will tell.  If it isn't, -cpu
host will expose it (and a good idea anyway to get best performance).

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