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Date: Wed, 3 Oct 2012 19:59:42 +0530
From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
To: Avi Kivity <avi@redhat.com>, Peter Zijlstra <peterz@infradead.org>
Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Marcelo Tosatti <mtosatti@redhat.com>, Ingo Molnar <mingo@redhat.com>,
        Rik van Riel <riel@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>, Andrew Jones <drjones@redhat.com>
Subject: Re: [PATCH RFC 0/2] kvm: Improving undercommit,overcommit scenarios
 in PLE handler
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Reply-To: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
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* Avi Kivity <avi@redhat.com> [2012-09-27 14:03:59]:

> On 09/27/2012 01:23 PM, Raghavendra K T wrote:
> >>
[...]
> > 2) looking at the result (comparing A & C) , I do feel we have
> > significant in iterating over vcpus (when compared to even vmexit)
> > so We still would need undercommit fix sugested by PeterZ (improving by
> > 140%). ?
> 
> Looking only at the current runqueue?  My worry is that it misses a lot
> of cases.  Maybe try the current runqueue first and then others.
> 

Okay. Do you mean we can have something like

+       if (rq->nr_running == 1 && p_rq->nr_running == 1) {
+               yielded = -ESRCH;
+               goto out_irq;
+       }

in the Peter's patch ?

( I thought lot about && or || . Both seem to have their own cons ).
But that should be only when we have short term imbalance, as PeterZ
told.

I am experimenting all these for V2 patch. Will come back with analysis
and patch.

> Or were you referring to something else?
>