From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754350AbZB1JZm (ORCPT ); Sat, 28 Feb 2009 04:25:42 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752961AbZB1JZ0 (ORCPT ); Sat, 28 Feb 2009 04:25:26 -0500 Received: from e23smtp08.au.ibm.com ([202.81.31.141]:58385 "EHLO e23smtp08.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752858AbZB1JZY (ORCPT ); Sat, 28 Feb 2009 04:25:24 -0500 Date: Sat, 28 Feb 2009 14:54:31 +0530 From: Dhaval Giani To: KAMEZAWA Hiroyuki Cc: Ken Chen , "linux-kernel@vger.kernel.org" , "menage@google.com" , "lizf@cn.fujitsu.com" , "balbir@linux.vnet.ibm.com" , mingo@elte.hu, "akpm@linux-foundation.org" Subject: Re: [PATCH] change cpuacct usage percpu format v2 Message-ID: <20090228092431.GA22310@linux.vnet.ibm.com> Reply-To: Dhaval Giani References: <20090227140537.390905c4.kamezawa.hiroyu@jp.fujitsu.com> <20090227162928.6225fc80.kamezawa.hiroyu@jp.fujitsu.com> <661fca240cb094bcf4d261ccebab9848.squirrel@webmail-b.css.fujitsu.com> <20090228011115.GC28769@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Feb 28, 2009 at 02:25:22PM +0900, KAMEZAWA Hiroyuki wrote: > Dhaval Giani wrote： > > On Sat, Feb 28, 2009 at 09:42:17AM +0900, KAMEZAWA Hiroyuki wrote: > >> KAMEZAWA Hiroyuki wrote： > >> BTW, current interface to reset cpuacct (write ops) just reset > >> specified level of cpuacct and will not clear other hierarchical levels. > >> Doesn't this behavior confuse software ? > >> > > > > hmmm. This got missed when we introduced hierarchy. But I wonder if it > > is needed? > > > IIUC, cpuacct.usage just shows sum of itself and all children's usage and > its own usage can be calclated by reading all usage of hierarchy. > So, reset ops seems to be a bit broken. > And by this, parent's usage can be smaller than children. > Actually now that I think about it, it does make sense, but when I started implementing it, a question popped up, if we reset a child's counter, then the parent is going to have a much greater usage than the sum of the children. I wonder if this behavior is fine? > How about adding limitation as "you can clear usage only when there are no > children" ? Maybe not very strange limitaton under hierarchical system. > Just the question I asked. Beyond that I don't think we should have such a limitation on reset. thanks, -- regards, Dhaval