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xen-devel
[Xen-devel] Re: [PATCH 2/3] kvm hypervisor : Add hypercalls to support p
 
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To:  | 
Jeremy Fitzhardinge <jeremy@xxxxxxxx> | 
 
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Subject:  | 
[Xen-devel] Re: [PATCH 2/3] kvm hypervisor : Add hypercalls to support pv-ticketlock | 
 
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From:  | 
Srivatsa Vaddagiri <vatsa@xxxxxxxxxxxxxxxxxx> | 
 
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Date:  | 
Wed, 19 Jan 2011 22:53:07 +0530 | 
 
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Cc:  | 
Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>,	Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>,	Nick Piggin <npiggin@xxxxxxxxx>, kvm@xxxxxxxxxxxxxxx,	Peter Zijlstra <peterz@xxxxxxxxxxxxx>,	Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>,	Jan Beulich <JBeulich@xxxxxxxxxx>, Eric Dumazet <dada1@xxxxxxxxxxxxx>,	Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>,	suzuki@xxxxxxxxxx, Avi Kivity <avi@xxxxxxxxxx>,	"H. Peter Anvin" <hpa@xxxxxxxxx>,	Américo Wang <xiyou.wangcong@xxxxxxxxx>,	Linux Virtualization <virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx> | 
 
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Delivery-date:  | 
Wed, 19 Jan 2011 09:25:15 -0800 | 
 
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<20110119171239.GB726@xxxxxxxxxxxxxxxxxx> | 
 
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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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