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

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Date:	Mon, 24 Jan 2011 09:49:58 -0800
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Rik van Riel <riel@...hat.com>
CC:	vatsa@...ux.vnet.ibm.com, Peter Zijlstra <peterz@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Nick Piggin <npiggin@...nel.dk>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Américo Wang <xiyou.wangcong@...il.com>,
	Eric Dumazet <dada1@...mosbay.com>,
	Jan Beulich <JBeulich@...ell.com>, Avi Kivity <avi@...hat.com>,
	Xen-devel <xen-devel@...ts.xensource.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linux Virtualization <virtualization@...ts.linux-foundation.org>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
	kvm@...r.kernel.org, suzuki@...ibm.com
Subject: Re: [PATCH 2/3] kvm hypervisor : Add hypercalls to support pv-ticketlock

On 01/22/2011 06:53 AM, Rik van Riel wrote:
> The main question that remains is whether the PV ticketlocks are
> a large enough improvement to also merge those.  I expect they
> will be, and we'll see so in the benchmark numbers.

The pathological worst-case of ticket locks in a virtual environment
isn't very hard to hit, so I expect they'll make a huge difference
there.   On lightly loaded systems (little or no CPU overcommit) then
they should be close to a no-op.

    J
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