[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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

On 04/01/2012 06:48 PM, Avi Kivity wrote:
On 03/30/2012 01:07 PM, Raghavendra K T wrote:
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;
-            } else if (pass&&  i>  last_boosted_vcpu)
+            } else if (pass == 2&&  i>  last_boosted_vcpu)
              if (vcpu == me)

Actually I think this is unneeded.  The loops tries to find vcpus that
are runnable but not running (vcpu_active(vcpu->wq)), and halted vcpus
don't match this condition.

I almost agree. But at corner of my thought,

Suppose there are 8 vcpus runnable out of which 4 of them are kicked
but not running, making yield_to those 4 vcpus would result in better
lock progress. no?

I still have little problem getting PLE setup, here (instead rebasing patches). Once I get PLE to get that running, and numbers prove no improvement, I will drop this idea.

Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.