On 04/02/2012 12:51 PM, Raghavendra K T wrote:On 04/01/2012 07:23 PM, Avi Kivity wrote:On 04/01/2012 04:48 PM, Raghavendra K T wrote:thatI have patch something like below in mind to try:
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index d3b98b1..5127668 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1608,15 +1608,18 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
* else and called schedule in __vcpu_run. Hopefully that
* VCPU is holding the lock that we need and will release it.
* We approximate round-robin by starting at the last boosted
VCPU.
+ * Priority is given to vcpu that are unhalted.
*/
- for (pass = 0; pass< 2&& !yielded; pass++) {
+ for (pass = 0; pass< 3&& !yielded; pass++) {
kvm_for_each_vcpu(i, vcpu, kvm) {
struct task_struct *task = NULL;
struct pid *pid;
- if (!pass&& i< last_boosted_vcpu) {
+ if (!pass&& !vcpu->pv_unhalted)
+ continue;
+ else if (pass == 1&& i< last_boosted_vcpu) {
i = last_boosted_vcpu;
continue;
- } else if (pass&& i> last_boosted_vcpu)
+ } else if (pass == 2&& i> last_boosted_vcpu)
break;
if (vcpu == me)
continue;
Actually I think this is unneeded. The loops tries to find vcpusvcpusare runnable but not running (vcpu_active(vcpu->wq)), and halteddon't match this condition.
Oh! I think I misinterpreted your statement. hmm I got it. you told to
remove if (vcpu == me) condition.
No, the entire patch is unneeded. My original comment was:
from the PLE handler, don't wake up a vcpu that is sleeping because itis waiting for a kick
But the PLE handler never wakes up sleeping vcpus anyway.
There's still a conflict with PLE in that it may trigger during the spin
phase and send a random yield_to() somewhere. Maybe it's sufficient to
tune the PLE timeout to be longer than the spinlock timeout.