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

[Avi Kivity <avi@xxxxxxxxxx>]

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;
>                  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.

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


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