Messages in this thread | | | Date | Mon, 07 Apr 2014 12:38:13 -0400 | From | Waiman Long <> | Subject | Re: [PATCH v8 00/10] qspinlock: a 4-byte queue spinlock with PV support |
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On 04/07/2014 02:14 AM, Raghavendra K T wrote: > > > I tested the v7,v8 of qspinlock with unfair config on kvm guest. > I was curious about unfair locks performance in undercommit cases. > (overcommit case is expected to perform well) > > 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?
> > 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). > >
What is the baseline for the performance improvement? Is it without the unfair lock and PV qspinlock?
-Longman
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