Re: [PATCH RFC V4 0/5] kvm : Paravirt-spinlock support for KVM guests

[Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>]

On 01/16/2012 07:53 PM, Alexander Graf wrote:
>
> On 16.01.2012, at 15:20, Srivatsa Vaddagiri wrote:
>
>> * Alexander Graf<agraf@suse.de>  [2012-01-16 04:57:45]:
>>
>>> Speaking of which - have you benchmarked performance degradation of pv ticket locks on bare metal?
>>
>> You mean, run kernel on bare metal with CONFIG_PARAVIRT_SPINLOCKS
>> enabled and compare how it performs with CONFIG_PARAVIRT_SPINLOCKS disabled for
>> some workload(s)?
>
> Yup
>
>>
>> In some sense, the 1x overcommitcase results posted does measure the overhead
>> of (pv-)spinlocks no? We don't see any overhead in that case for atleast
>> kernbench ..
>>
>>> Result for Non PLE machine :
>>> ============================
>>
>> [snip]
>>
>>> Kernbench:
>>>                BASE                    BASE+patch
>
> What is BASE really? Is BASE already with the PV spinlocks enabled? I'm having a hard time understanding which tree you're working against, since the prerequisites aren't upstream yet.
>
>
> Alex

Sorry for confusion, I think I was little imprecise on the BASE.

The BASE is pre 3.2.0 + Jeremy's following patches:
xadd (https://lkml.org/lkml/2011/10/4/328)
x86/ticketlocklock  (https://lkml.org/lkml/2011/10/12/496).
So this would have ticketlock cleanups from Jeremy and
CONFIG_PARAVIRT_SPINLOCKS=y

BASE+patch = pre 3.2.0 + Jeremy's above patches + above V5 PV spinlock
series and CONFIG_PARAVIRT_SPINLOCKS=y

In both the cases  CONFIG_PARAVIRT_SPINLOCKS=y.

So let,
A. pre-3.2.0 with CONFIG_PARAVIRT_SPINLOCKS = n
B. pre-3.2.0 + Jeremy's above patches with CONFIG_PARAVIRT_SPINLOCKS = n
C. pre-3.2.0 + Jeremy's above patches with CONFIG_PARAVIRT_SPINLOCKS = y
D. pre-3.2.0 + Jeremy's above patches + V5 patches with 
CONFIG_PARAVIRT_SPINLOCKS = n
E. pre-3.2.0 + Jeremy's above patches + V5 patches with 
CONFIG_PARAVIRT_SPINLOCKS = y

is it performance of A vs E ? (currently C vs E)

Please let me know the configuration expected for testing.

Jeremy,
I would be happy to test A vs B vs C vs E, for some workload of interest 
if you wish, for your upcoming patches.

Thanks and Regards
Raghu

>
>>>                %improvement
>>>                mean (sd)               mean (sd)
>>> Scenario A:
>>> case 1x:	 164.233 (16.5506)	 163.584 (15.4598	0.39517
>>
>> [snip]
>>
>>> Result for PLE machine:
>>> ======================
>>
>> [snip]
>>> Kernbench:
>>>                BASE                    BASE+patch
>>>                %improvement
>>>                mean (sd)               mean (sd)
>>> Scenario A:
>>> case 1x:	 161.263 (56.518)        159.635 (40.5621)	1.00953
>>
>> - vatsa
>>
>
>