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    SubjectRe: [PATCH RFC V6 0/11] Paravirtualized ticketlocks
    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:
    > >>>> 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;
    > >>>>
    > >>>
    > >>> 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.
    > >>>
    >
    > 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 it
    is 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.


    --
    error compiling committee.c: too many arguments to function



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