From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759661AbZAMJF3 (ORCPT ); Tue, 13 Jan 2009 04:05:29 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756066AbZAMJEM (ORCPT ); Tue, 13 Jan 2009 04:04:12 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:62707 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1759206AbZAMJEB (ORCPT ); Tue, 13 Jan 2009 04:04:01 -0500 Message-ID: <496C58C9.5080807@cn.fujitsu.com> Date: Tue, 13 Jan 2009 17:03:05 +0800 From: Li Zefan User-Agent: Thunderbird 2.0.0.9 (X11/20071115) MIME-Version: 1.0 To: Frederic Weisbecker CC: "Paul E. McKenney" , Ingo Molnar , LKML , Steven Rostedt Subject: Re: [PATCH] rcu: convert rcupreempt trace to seq file References: <496852DE.7080802@cn.fujitsu.com> <20090110223151.GD7061@linux.vnet.ibm.com> <20090111013940.GL12885@elte.hu> <20090111050129.GA6131@nowhere> <496C0850.8010103@cn.fujitsu.com> <20090113084905.GA5837@nowhere> In-Reply-To: <20090113084905.GA5837@nowhere> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Frederic Weisbecker wrote: > On Tue, Jan 13, 2009 at 11:19:44AM +0800, Li Zefan wrote: >>> Indeed! >>> >>> The debugfs and seqfile handling and handled in the statistical >>> tracing engine. >>> >>> You just have to provide an iterator for your stat entries through two callbacks: >>> >>> _ stat_start() -> gives the first entry >>> _ stat_next() -> iterates over the next entry >>> >>> And an output callback >>> >>> _ stat_show() -> print one entry from your stat list >>> >>> And two optional things: >>> >>> _ stat_cmp() -> compare two entries, useful if you want your stats to be sorted >>> _ stat_headers() -> provide the first line in your stat file, typically to describe your columns >>> >>> The last thing you need is to give a name to your trace file. >>> You will retrieve it into /debugfs/tracing/trace_stat/your_file_name as a current snapshot >>> of your stats. >>> >>> It is currently used by the branch tracer, and by a pending patch for a new workqueue >>> tracer which will provide you a simple example. >>> >>> If you have any question about how to use it, don't hesitate to ask. >>> >> Hi Frederic, >> >> I've converted rcupreempt to use trace points, but I don't see much advantage to use >> trace stat instead of using seq_file directly.. And can you add support to allow >> me to provide stat_show() only ? I think it's common that the stat file has only >> one entry. >> >> >> Regards >> Li Zefan > > > It simplifies (I hope) a bit the seqfile. > The interface is very similar except that you don't need to deal > with debugfs stuffs, sorting, and position inside the seqfile. > And it unifies the stat files into a common directory instead of > having them grained into a mess of debugfs filesystem.... > OK. It makes things easier for some cases. :) But will trace_stat/ become a mess when there are many stat files in it ? Does it make sense to support making subdir in trace_stat/ ? > I could let it handle only stat_show when you have only one entry but that > would break the sense of stat_show. > If it's so common to have only one stat entry, perhaps I could provide a special callback > for that, something like stat_show_unique()... > > Hm? > stat_show_single() ? I don't know which name is better. Like it's common to use single_open with seq_file, I think it's needed as we add more stat files into trace_stat. Regards Li Zefan