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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <506D6B64.6030907@linux.vnet.ibm.com>
Date:	Thu, 04 Oct 2012 16:26:36 +0530
From:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
To:	Avi Kivity <avi@...hat.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 10:55 PM, Avi Kivity wrote:
> 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?

p_rq is the run queue of target vcpu.
What I was trying below was to address Rik concern. Suppose
rq of source vcpu has one task, but target probably has two task,
with a eligible vcpu waiting to be scheduled.

>
> 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

I think you are saying we have to check the run queue of the
source vcpu, if we have a vcpu belonging to same VM and try yield to 
that? ignoring whatever the target vcpu we received for yield_to.

Or is it that kvm_vcpu_yield_to should now check the vcpus of same vm
belonging to same run queue first. If we don't succeed, go again for
a vcpu in different runqueue.
Does it add more overhead especially in <= 1x scenario?

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/