Subject: Re: [PATCH] sched: cpuacct: Use bigger percpu counter batch values
 for stats counters
From: Peter Zijlstra <peterz@infradead.org>
To: Anton Blanchard <anton@samba.org>
Cc: Bharata B Rao <bharata@linux.vnet.ibm.com>,
       KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
       Ingo Molnar <mingo@elte.hu>, Balbir Singh <balbir@linux.vnet.ibm.com>,
       mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org,
       schwidefsky@de.ibm.com, balajirrao@gmail.com, dhaval@linux.vnet.ibm.com,
       tglx@linutronix.de, kamezawa.hiroyu@jp.fujitsu.com,
       akpm@linux-foundation.org, Tony Luck <tony.luck@intel.com>,
       Fenghua Yu <fenghua.yu@intel.com>,
       Heiko Carstens <heiko.carstens@de.ibm.com>, linux390@de.ibm.com
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Date: Mon, 18 Jan 2010 09:34:41 +0100
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On Mon, 2010-01-18 at 19:21 +1100, Anton Blanchard wrote:
> Hi Peter,
> 
> > Seems like a good idea, but isn't that batch number rather static? If
> > so, computing it in some init path would save that multiply on the
> > actual accounting path.
> 
> It is mostly static, but percpu_counter_batch does change with hotplug
> operations. Adding a hotplug notifier felt like a lot of work but I was
> worried we have issues if we didn't scale with hotplug add operations.

OK, trading a notifier for a mult might be worth it, we'll see if
someone complains ;-)

Lets got with this for now.

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