linux-kernel - Re: [PATCH 00/20] x86: ticket lock rewrite and paravirtualization

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Message-ID: <4CE1920F.5000509@zytor.com>
Date:	Mon, 15 Nov 2010 12:03:27 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jan Beulich <JBeulich@...ell.com>, Avi Kivity <avi@...hat.com>,
	Xen-devel <xen-devel@...ts.xensource.com>,
	Linux Virtualization <virtualization@...ts.linux-foundation.org>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Subject: Re: [PATCH 00/20] x86: ticket lock rewrite and paravirtualization

On 11/15/2010 12:00 PM, Jeremy Fitzhardinge wrote:
> 
> Another approach I discussed with PeterZ and Mathieu is to steal the LSB
> of the ticket counters (halving the max CPU count) to use as a "there is
> someone in slowpath waiting on this lock".  But I haven't spent the time
> to work out an algorithm to maintain that flag (or flags, since there
> are bits available) in a correct and efficient way.
> 

Definitely worth pondering.

	-hpa

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