Re: [Xen-devel] [PATCH RFC V6 0/11] Paravirtualized ticketlocks

[Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>]

On 03/29/2012 11:33 PM, Raghavendra K T wrote:
> On 03/29/2012 03:28 PM, Avi Kivity wrote:
> > On 03/28/2012 08:21 PM, Raghavendra K T wrote:
> I really like below ideas. Thanks for that!.
>
> > - from the PLE handler, don't wake up a vcpu that is sleeping because it
> > is waiting for a kick
> How about, adding another pass in the beginning of kvm_vcpu_on_spin()
> to check if any vcpu is already kicked. This would almost result in
> yield_to(kicked_vcpu). IMO this is also worth trying.
>
> will try above ideas soon.
I 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;


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