Re: [PATCH v8 00/10] qspinlock: a 4-byte queue spinlock with PV support
From: Raghavendra K T
Date: Mon Apr 07 2014 - 13:47:04 EST
On 04/07/2014 10:08 PM, Waiman Long wrote:
On 04/07/2014 02:14 AM, Raghavendra K T wrote:
[...]
But I am seeing hang in overcommit cases. Gdb showed that many vcpus
are halted and there was no progress. Suspecting the problem /race with
halting, I removed the halt() part of kvm_hibernate(). I am yet to
take a closer look at the code on halt() related changes.
It seems like there may still be race conditions where the current code
is not handling correctly. I will look into that to see where the
problem is. BTW, what test do you use to produce the hang condition?
Running ebizzy on 2 of the vms simultaneously (for sometime in repeated
loop) could reproduce it.
Patch series with that change gave around 20% improvement for dbench
2x and 30% improvement for ebizzy 2x cases. (1x has no significant
loss/gain).
While at it, Just a correction it was 30% for ebizzy1.5x and around
80% for ebizzy 2x.
What is the baseline for the performance improvement? Is it without the
unfair lock and PV qspinlock?
Baseline was 3.14-rc8 without any of the qspin patch series.
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