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Date: Mon, 12 Sep 2011 18:38:42 +0200
From: Andi Kleen <andi@firstfloor.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andi Kleen <andi@firstfloor.org>, Peter Zijlstra <peterz@infradead.org>,
        Huang Ying <ying.huang@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 8/5] llist: Remove cpu_relax() usage in cmpxchg loops
Message-ID: <20110912163842.GO7761@one.firstfloor.org>
References: <1315461646-1379-1-git-send-email-ying.huang@intel.com> <1315836358.26517.43.camel@twins> <20110912142305.GN7761@one.firstfloor.org> <20110912144706.GA21716@Krystal>
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> so basically, in typical locking primitives (spinlock), it looks like
> lower power consumption is preferred over getting the raw maximal

It's not only power, its:
- Allow the other siblings make more progress on SMT
- Do some backoff to stress the interconnect less (this is important on >2S):
A tight loop which constantly writes is a extremly stressfull pattern.
- Save some power by allowing the CPU to do more clock gating

-Andi