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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>
Subject: Re: [PATCH 8/5] llist: Remove cpu_relax() usage in cmpxchg loops
Date: Mon, 12 Sep 2011 16:32:10 +0200	[thread overview]
Message-ID: <1315837930.26517.49.camel@twins> (raw)
In-Reply-To: <4E6E1693.7080606@redhat.com>

On Mon, 2011-09-12 at 17:26 +0300, Avi Kivity wrote:
> On 09/12/2011 05:05 PM, Peter Zijlstra wrote:
> > Subject: llist: Remove cpu_relax() usage in cmpxchg loops
> > From: Peter Zijlstra<a.p.zijlstra@chello.nl>
> > Date: Mon Sep 12 15:50:49 CEST 2011
> >
> > Initial benchmarks show they're a net loss (2 socket wsm):
> >
> >   $ for i in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor ; do echo performance>  $i; done
> >   $ echo 4096 32000 64 128>  /proc/sys/kernel/sem
> >   $ ./sembench -t 2048 -w 1900 -o 0
> >
> 
> We hyperthreading enabled, and were all threads loaded?  cpu_relax 
> allows the other thread to make more progress while the spinner relaxes.

Yeah, with HT enabled, the benchmark runs 2048 tasks and does 1900 task
bulk wakeups or so. Forgot the details, but it basically stresses the
sleep+wakeup paths like nobodies business.



  reply	other threads:[~2011-09-12 14:32 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
2011-09-12 14:26   ` Avi Kivity
2011-09-12 14:32     ` Peter Zijlstra [this message]
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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