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Date:	Sun, 30 Sep 2012 10:24:51 +0200
From:	Avi Kivity <>
CC:	Raghavendra K T <>,
	Peter Zijlstra <>,
	"H. Peter Anvin" <>,
	Marcelo Tosatti <>,
	Ingo Molnar <>, Rik van Riel <>,
	Srikar <>,
	"Nikunj A. Dadhania" <>,
	KVM <>, Jiannan Ouyang <>,
	chegu vinod <>,
	LKML <>,
	Srivatsa Vaddagiri <>,
	Gleb Natapov <>,
	Andrew Jones <>
Subject: Re: [PATCH RFC 0/2] kvm: Improving undercommit,overcommit scenarios
 in PLE handler

On 09/28/2012 01:40 PM, Andrew Theurer wrote:
>> >>
>> >> IIRC, with defer preemption :
>> >> we will have hook in spinlock/unlock path to measure depth of lock held,
>> >> and shared with host scheduler (may be via MSRs now).
>> >> Host scheduler 'prefers' not to preempt lock holding vcpu. (or rather
>> >> give say one chance.
>> >
>> > A downside is that we have to do that even when undercommitted.
> Hopefully vcpu preemption is very rare when undercommitted, so it should
> not happen much at all.

As soon as you're preempted, you're effectively overcommitted (even if
the system as a whole is undercommitted).  What I meant was that you
need to communicate your lock state to the host, and with fine-grained
locking this can happen a lot.  It may be as simple as an
increment/decrement instruction though.

error compiling committee.c: too many arguments to function
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