On 09/21/2012 08:00 AM, Raghavendra K T wrote:
From: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx> When total number of VCPUs of system is less than or equal to physical CPUs, PLE exits become costly since each VCPU can have dedicated PCPU, and trying to find a target VCPU to yield_to just burns time in PLE handler. This patch reduces overhead, by simply doing a return in such scenarios by checking the length of current cpu runqueue.
I am not convinced this is the way to go. The VCPU that is holding the lock, and is not releasing it, probably got scheduled out. That implies that VCPU is on a runqueue with at least one other task.
--- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1629,6 +1629,9 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me) int pass; int i; + if (unlikely(rq_nr_running() == 1)) + return; + kvm_vcpu_set_in_spin_loop(me, true); /* * We boost the priority of a VCPU that is runnable but not
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