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

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Message-ID: <20110912163842.GO7761@one.firstfloor.org>
Date:	Mon, 12 Sep 2011 18:38:42 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Huang Ying <ying.huang@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 8/5] llist: Remove cpu_relax() usage in cmpxchg loops

> 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
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