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From: Peter Zijlstra <peterz@infradead.org>
To: Andi Kleen <andi@firstfloor.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	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
Date: Mon, 12 Sep 2011 20:53:28 +0200	[thread overview]
Message-ID: <1315853608.575.1.camel@twins> (raw)
In-Reply-To: <20110912163842.GO7761@one.firstfloor.org>

On Mon, 2011-09-12 at 18:38 +0200, Andi Kleen wrote:
> > 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

If you're hitting a cmpxchg hard enough for any of those to make a
difference you're doing it wrong.

  reply	other threads:[~2011-09-12 18:53 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-09-08  6:00 [PATCH -mm -v2 0/5] irq_work, Use llist in irq_work Huang Ying
2011-09-08  6:00 ` [PATCH -mm -v2 1/5] llist, Make all llist functions inline Huang Ying
2011-09-08  6:00 ` [PATCH -mm -v2 2/5] llist, Define macro to check NMI safe cmpxchg Huang Ying
2011-09-08  6:00 ` [PATCH -mm -v2 3/5] llist, Move cpu_relax after cmpxchg Huang Ying
2011-09-08  6:00 ` [PATCH -mm -v2 4/5] llist, Return whether list is empty before adding in llist_add Huang Ying
2011-09-08  6:00 ` [PATCH -mm -v2 5/5] irq_work, Use llist in irq_work Huang Ying
2011-09-12 14:05 ` [PATCH 6/5] llist: Add llist_next() Peter Zijlstra
2011-09-12 14:05 ` [PATCH 7/5] sched: Convert to use llist Peter Zijlstra
2011-09-12 14:05 ` [PATCH 8/5] llist: Remove cpu_relax() usage in cmpxchg loops Peter Zijlstra
2011-09-12 14:23   ` Andi Kleen
2011-09-12 14:23     ` Peter Zijlstra
2011-09-12 14:47     ` Mathieu Desnoyers
2011-09-12 15:09       ` Peter Zijlstra
2011-09-12 15:24       ` Peter Zijlstra
2011-09-12 16:38       ` Andi Kleen
2011-09-12 18:53         ` Peter Zijlstra [this message]
2011-09-12 14:26   ` Avi Kivity
2011-09-12 14:32     ` Peter Zijlstra
2011-09-13 11:43       ` Avi Kivity
2011-09-13 14:22         ` Peter Zijlstra
2011-09-13 14:51           ` Avi Kivity
2011-09-13 14:53             ` Peter Zijlstra
2011-09-12 14:06 ` [PATCH -mm -v2 0/5] irq_work, Use llist in irq_work Peter Zijlstra

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