Messages in this thread |  | | Date | Thu, 09 Apr 2015 09:16:24 -0400 | From | Rik van Riel <> | Subject | Re: [PATCH v15 16/16] unfair qspinlock: a queue based unfair lock |
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On 04/09/2015 03:01 AM, Peter Zijlstra wrote: > On Wed, Apr 08, 2015 at 02:32:19PM -0400, Waiman Long wrote: >> For a virtual guest with the qspinlock patch, a simple unfair byte lock >> will be used if PV spinlock is not configured in or the hypervisor >> isn't either KVM or Xen. The byte lock works fine with small guest >> of just a few vCPUs. On a much larger guest, however, byte lock can >> have serious performance problem. > > Who cares?
There are some people out there running guests with dozens of vCPUs. If the code exists to make those setups run better, is there a good reason not to use it?
Having said that, only KVM and Xen seem to support very large guests, and PV spinlock is available there.
I believe both VMware and Hyperv have a 32 VCPU limit, anyway.
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