[Xen-devel] Re: [PATCH 2/3] kvm hypervisor : Add hypercalls to support pv-ticketlock

[Srivatsa Vaddagiri <vatsa@xxxxxxxxxxxxxxxxxx>]

On Wed, Jan 19, 2011 at 10:42:39PM +0530, Srivatsa Vaddagiri wrote:
> Add two hypercalls to KVM hypervisor to support pv-ticketlocks.
> 
> KVM_HC_WAIT_FOR_KICK blocks the calling vcpu until another vcpu kicks it or it
> is woken up because of an event like interrupt.

One possibility is to extend this hypercall to do a directed yield as well, 
which needs some more thought. Another issue that needs to be resolved with
pv-ticketlocks is the impact on intra-VM fairness. A guest experiencing heavy
contention can keep yielding cpu, allowing other VMs to get more time than they
deserve.

- vatsa

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