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Subject: Re: [PATCH 8/5] llist: Remove cpu_relax() usage in cmpxchg loops
From: Peter Zijlstra <peterz@infradead.org>
To: Avi Kivity <avi@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org, Andi Kleen <andi@firstfloor.org>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Tue, 13 Sep 2011 16:22:04 +0200
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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.