linux-kernel - Re: [PATCH 8/5] llist: Remove cpu

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Message-ID: <1315923724.5977.15.camel@twins>
Date:	Tue, 13 Sep 2011 16:22:04 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Avi Kivity <avi@...hat.com>
Cc:	Huang Ying <ying.huang@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Andi Kleen <andi@...stfloor.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [PATCH 8/5] llist: Remove cpu_relax() usage in cmpxchg loops

On Tue, 2011-09-13 at 14:43 +0300, Avi Kivity wrote:

> Another issue is that hypervisors use PAUSE to detect a spinning guest 
> and issue a directed yield to another vcpu.  But for cmpxchg loops, the 
> "spinner" would just commit on the next loop, no?  So I think there's no 
> objection from that front.

Right, we shouldn't ever spend a significant amount spinning on a
cmpxchg. If we do we need to fix that instead.
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