From mboxrd@z Thu Jan  1 00:00:00 1970
From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Subject: Re: [PATCH RFC 1/2] KVM: don't check for PF_VCPU when yielding
Date: Fri, 28 Nov 2014 17:10:25 +0530
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Cc: David Hildenbrand <dahi@linux.vnet.ibm.com>,
	KVM <kvm@vger.kernel.org>, Paolo Bonzini <pbonzini@redhat.com>,
	Gleb Natapov <gleb@kernel.org>, jfrei@linux.vnet.ibm.com,
	Cornelia Huck <cornelia.huck@de.ibm.com>,
	Michael Mueller <mimu@linux.vnet.ibm.com>,
	raghavendra.kt.linux@gmail.com
To: Christian Borntraeger <borntraeger@de.ibm.com>
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On 11/28/2014 04:28 PM, Christian Borntraeger wrote:
> Am 28.11.2014 um 11:08 schrieb Raghavendra KT:
>> Was able to test the patch, here is the result: I have not tested with
>> bigger VMs though. Results make it difficult to talk about any side
>> effect of
>> patch if any.
>
> Thanks a log.
>
> If our assumption is correct, then this patch should have no side effect on x86. Do you have any confidence guess if the numbers below mean: no-change vs. regression vs improvement?
>

I am seeing very small improvement in <= 1x commit cases
and for >1x overcommit, a very slight regression. But considering the
test environment noises, I do not see much effect from the
patch.

But I admit, I have not explored deeply about,
1. assumption of preempted approximately equals PF_VCPU case logic,
2. whether it helps for any future usages of yield_to against current
sole usage of virtualization.