linux-kernel - Re: [PATCH] sched: cpuacct: Use bigger percpu counter batch values for stats counters

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Message-ID: <20100118082151.GU12666@kryten>
Date:	Mon, 18 Jan 2010 19:21:51 +1100
From:	Anton Blanchard <anton@...ba.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Bharata B Rao <bharata@...ux.vnet.ibm.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Ingo Molnar <mingo@...e.hu>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>, mingo@...hat.com,
	hpa@...or.com, linux-kernel@...r.kernel.org,
	schwidefsky@...ibm.com, balajirrao@...il.com,
	dhaval@...ux.vnet.ibm.com, tglx@...utronix.de,
	kamezawa.hiroyu@...fujitsu.com, akpm@...ux-foundation.org,
	Tony Luck <tony.luck@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>, linux390@...ibm.com
Subject: Re: [PATCH] sched: cpuacct: Use bigger percpu counter batch values
 for stats counters


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.

Anton
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