linux-kernel - Re: [PATCH RFC V11 15/18] kvm : Paravirtual ticketlocks support for linux guests running on KVM hypervisor

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Message-ID: <51FB7F6A.2020804@linux.vnet.ibm.com>
Date:	Fri, 02 Aug 2013 15:14:10 +0530
From:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
To:	Ingo Molnar <mingo@...nel.org>
CC:	Gleb Natapov <gleb@...hat.com>, mingo@...hat.com, x86@...nel.org,
	tglx@...utronix.de, jeremy@...p.org, konrad.wilk@...cle.com,
	hpa@...or.com, pbonzini@...hat.com, linux-doc@...r.kernel.org,
	habanero@...ux.vnet.ibm.com, xen-devel@...ts.xensource.com,
	peterz@...radead.org, mtosatti@...hat.com,
	stefano.stabellini@...citrix.com, andi@...stfloor.org,
	attilio.rao@...rix.com, ouyang@...pitt.edu, gregkh@...e.de,
	agraf@...e.de, chegu_vinod@...com, torvalds@...ux-foundation.org,
	avi.kivity@...il.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, riel@...hat.com, drjones@...hat.com,
	virtualization@...ts.linux-foundation.org,
	srivatsa.vaddagiri@...il.com
Subject: Re: [PATCH RFC V11 15/18] kvm : Paravirtual ticketlocks support for
 linux guests running on KVM hypervisor

On 08/02/2013 02:53 PM, Ingo Molnar wrote:
>
> * Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com> wrote:
>
>> On 08/01/2013 02:34 PM, Raghavendra K T wrote:
>>> On 08/01/2013 01:15 PM, Gleb Natapov wrote:
>>>>> Shall I consider this as an ack for kvm part?
>>>>>
>>>> For everything except 18/18. For that I still want to see numbers. But
>>>> 18/18 is pretty independent from the reset of the series so it should
>>>> not stop the reset from going in.
>>>
>>> Yes. agreed.
>>> I am going to evaluate patch 18 separately and come with results for
>>> that. Now we can consider only 1-17 patches.
>>>
>>
>> Gleb,
>>
>> 32 core machine with HT off 32 vcpu guests.
>> base = 3.11-rc + patch 1 -17 pvspinlock_v11
>> patched = base + patch 18
>>
>> +-----------+-----------+-----------+------------+-----------+
>>                    dbench  (Throughput in MB/sec higher is better)
>> +-----------+-----------+-----------+------------+-----------+
>>        base      stdev       patched    stdev       %improvement
>> +-----------+-----------+-----------+------------+-----------+
>> 1x 14584.3800   146.9074   14705.1000   163.1060     0.82773
>> 2x  1713.7300    32.8750    1717.3200    45.5979     0.20948
>> 3x   967.8212    42.0257     971.8855    18.8532     0.41994
>> 4x   685.2764    25.7150     694.5881     8.3907     1.35882
>> +-----------+-----------+-----------+------------+-----------+
>
> Please list stddev in percentage as well ...

Sure. will do this from next time.

>
> a blind stab gave me these figures:
>
>>        base      stdev       patched    stdev       %improvement
>> 3x   967.8212    4.3%     971.8855      1.8%     0.4
>
> That makes the improvement an order of magnitude smaller than the noise of
> the measurement ... i.e. totally inconclusive.

Okay. agreed.

I always had seen the positive effect of the patch since it uses ple
handler heuristics, and thus avoiding the directed yield to vcpu's in
halt handler. But the current results clearly does not conclude
anything favoring that. :(

So please drop patch 18 for now.

>
> Also please cut the excessive decimal points: with 2-4% noise what point
> is there in 5 decimal point results??

Yes.

Ingo, do you think now the patch series (patch 1 to 17) are in good
shape? or please let me know if you have any concerns to be
addressed.



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