From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: bharata@linux.vnet.ibm.com
Subject: Re: [PATCH] cpuacct: VIRT_CPU_ACCOUNTING don't prevent percpu cputime count
Cc: kosaki.motohiro@jp.fujitsu.com, LKML <linux-kernel@vger.kernel.org>,
       Balaji Rao <balajirrao@gmail.com>,
       Dhaval Giani <dhaval@linux.vnet.ibm.com>,
       KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>,
       Balbir Singh <balbir@linux.vnet.ibm.com>, Ingo Molnar <mingo@elte.hu>,
       Martin Schwidefsky <schwidefsky@de.ibm.com>,
       seto.hidetoshi@jp.fujitsu.com
In-Reply-To: <20090428075055.GD3825@in.ibm.com>
References: <20090428163509.EBCF.A69D9226@jp.fujitsu.com> <20090428075055.GD3825@in.ibm.com>
Message-Id: <20090428165203.EBD5.A69D9226@jp.fujitsu.com>
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Date: Tue, 28 Apr 2009 17:10:47 +0900 (JST)
Sender: linux-kernel-owner@vger.kernel.org
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> On Tue, Apr 28, 2009 at 04:38:51PM +0900, KOSAKI Motohiro wrote:
> > > On Tue, Apr 28, 2009 at 03:53:32PM +0900, KOSAKI Motohiro wrote:
> > 
> > > BTW, did you observe any real problem with the percpu counter spinlock ?
> > 
> > No.
> > I review percpu_counter() caller recently and it seems stragen usage.
> > 
> 
> I should have phrased the question better ...
> 
> So have you found any performance degradation with any benchmarks/workloads
> on archs which define VIRT_CPU_ACCOUNTING due to percpu_counter spinlock
> being taken on every tick ? If the answer is no, don't you think we could
> wait before making the kind of change you are proposing ?

maybe, I don't understand your point.
I don't oppose you wait something :)


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