linux-kernel - Re: [PATCH RFC 0/2] kvm: Improving undercommit,overcommit scenarios in PLE handler

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Message-ID: <506C7524.2010103@redhat.com>
Date:	Wed, 03 Oct 2012 19:25:56 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
CC:	Peter Zijlstra <peterz@...radead.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Ingo Molnar <mingo@...hat.com>, Rik van Riel <riel@...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>,
	Andrew Jones <drjones@...hat.com>
Subject: Re: [PATCH RFC 0/2] kvm: Improving undercommit,overcommit scenarios
 in PLE handler

On 10/03/2012 04:29 PM, Raghavendra K T wrote:
> * Avi Kivity <avi@...hat.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'm missing the context.  What is p_rq?

What I mean was:

  if can_yield_to_process_in_current_rq
     do that
  else if can_yield_to_process_in_other_rq
     do that
  else
     return -ESRCH


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