Re: [PATCH RFC 3/4] Paravirtualized spinlock implementation for KVMguests

From: Avi Kivity
Date: Mon Aug 02 2010 - 04:53:19 EST

On 07/26/2010 09:15 AM, Srivatsa Vaddagiri wrote:
Paravirtual spinlock implementation for KVM guests, based heavily on Xen guest's
spinlock implementation.

+static void kvm_spin_unlock(struct arch_spinlock *lock)
+ struct kvm_spinlock *sl = (struct kvm_spinlock *)lock;
+ ADD_STATS(released, 1);
+ smp_wmb(); /* make sure no writes get moved after unlock */
+ sl->lock = 0; /* release lock */

Wait, no wakeup?

So it is a yield, not a sleep. I'm worried it could seriously impact fairness when one non-contending guest (or non-pv) is overcommitted together with a spin-yield guest.

error compiling committee.c: too many arguments to function

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