On 12/03/2010 12:41 AM, Chris Wright wrote:
* Rik van Riel (r...@redhat.com) wrote:
> When running SMP virtual machines, it is possible for one VCPU to be
> spinning on a spinlock, while the VCPU that holds the spinlock is not
> currently running, because the host scheduler preempted it to run
> something else.
>
> Both Intel and AMD CPUs have a feature that detects when a virtual
> CPU is spinning on a lock and will trap to the host.
>
> The current KVM code sleeps for a bit whenever that happens, which
> results in eg. a 64 VCPU Windows guest taking forever and a bit to
> boot up. This is because the VCPU holding the lock is actually
> running and not sleeping, so the pause is counter-productive.
Seems like simply increasing the spin window help in that case? Or is
it just too contended a lock (I think they use mcs locks, so I can see a
single wrong sleep causing real contention problems).
It may, but that just pushes the problem to a more contended lock or to
a higher vcpu count. We want something that works after PLE threshold
tuning has failed.
--
error compiling committee.c: too many arguments to function
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