From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH RFC 1/2] kvm: Handle undercommitted guest case in PLE
 handler
Date: Thu, 04 Oct 2012 15:07:18 +0200
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Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
	Rik van Riel <riel@redhat.com>,
	"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	Srikar <srikar@linux.vnet.ibm.com>,
	"Nikunj A. Dadhania" <nikunj@linux.vnet.ibm.com>,
	KVM <kvm@vger.kernel.org>, Jiannan Ouyang <ouyang@cs.pitt.edu>,
	chegu vinod <chegu_vinod@hp.com>,
	"Andrew M. Theurer" <habanero@linux.vnet.ibm.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Srivatsa Vaddagiri <srivatsa.vaddagiri@gmail.com>,
	Gleb Natapov <gleb@redhat.com>
To: Avi Kivity <avi@redhat.com>
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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.