Re: [PATCH v10 18/19] pvqspinlock, x86: Enable PV qspinlock PV for KVM

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On 05/07/2014 03:07 PM, Konrad Rzeszutek Wilk wrote:
Raghavendra KT had done some performance testing on this patch with
the following results:

Overall we are seeing good improvement for pv-unfair version.

System: 32 cpu sandybridge with HT on (4 node with 32 GB each)
Guest : 8GB with 16 vcpu/VM.
Average was taken over 8-10 data points.

Base = 3.15-rc2  with PRAVIRT_SPINLOCK = y

A = 3.15-rc2 + qspinlock v9 patch with QUEUE_SPINLOCK = y
PRAVIRT_SPINLOCK = y PARAVIRT_UNFAIR_LOCKS = y (unfair lock)

B =  3.15-rc2 + qspinlock v9 patch with QUEUE_SPINLOCK = y
PRAVIRT_SPINLOCK = n PARAVIRT_UNFAIR_LOCKS = n
(queue spinlock without paravirt)

C = 3.15-rc2 + qspinlock v9 patch with  QUEUE_SPINLOCK = y
PRAVIRT_SPINLOCK = y  PARAVIRT_UNFAIR_LOCKS = n
(queue spinlock with paravirt)
Could you do s/PRAVIRT/PARAVIRT/ please?


Sorry for the typo, I didn't check the text carefully enough when I cut-and-paste it from Raghavendra's email.

Ebizzy %improvements
====================
overcommit  A            B            C
0.5x     4.4265        2.0611       1.5824
1.0x     0.9015       -7.7828       4.5443
1.5x    46.1162       -2.9845      -3.5046
2.0x    99.8150       -2.7116       4.7461
Considering B sucks

Yes, I don't expect the plain qspinlock code will perform well in a guest without either unfair or pvspinlock support.

-Longman
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