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

[Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>]

On 01/16/2012 07:53 PM, Alexander Graf wrote:
> On 16.01.2012, at 15:20, Srivatsa Vaddagiri wrote:
>
> > * Alexander Graf<agraf@xxxxxxx>  [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

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