On 16.01.2012, at 19:38, Raghavendra K T wrote:

On 01/16/2012 07:53 PM, Alexander Graf wrote:

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On 16.01.2012, at 15:20, Srivatsa Vaddagiri wrote:

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* Alexander Graf[off-list ref]  [2012-01-16 04:57:45]:

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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

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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 ..

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Result for Non PLE machine :
============================

[snip]

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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)

Since D and E only matter with KVM in use, yes, I'm mostly interested in A, B and C :).


Alex