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

To: vatsa@xxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] Re: [PATCH 2/3] kvm hypervisor : Add hypercalls to support pv-ticketlock
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Thu, 20 Jan 2011 09:49:35 -0800
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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On 01/20/2011 03:42 AM, Srivatsa Vaddagiri wrote:
> On Wed, Jan 19, 2011 at 10:53:52AM -0800, Jeremy Fitzhardinge wrote:
>>> The reason for wanting this should be clear I guess, it allows PI.
>> Well, if we can expand the spinlock to include an owner, then all this
>> becomes moot...
> How so? Having an owner will not eliminate the need for pv-ticketlocks
> afaict. We still need a mechanism to reduce latency in scheduling the next
> thread-in-waiting, which is achieved by your patches. 

No, sorry, I should have been clearer.  I meant that going to the effort
of not increasing the lock size to record "in slowpath" state.

    J

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