From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751782AbZAKFQS (ORCPT ); Sun, 11 Jan 2009 00:16:18 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750779AbZAKFQG (ORCPT ); Sun, 11 Jan 2009 00:16:06 -0500 Received: from e5.ny.us.ibm.com ([32.97.182.145]:56111 "EHLO e5.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750749AbZAKFQE (ORCPT ); Sun, 11 Jan 2009 00:16:04 -0500 Date: Sat, 10 Jan 2009 21:16:04 -0800 From: "Paul E. McKenney" To: Frederic Weisbecker Cc: Ingo Molnar , Li Zefan , LKML , Steven Rostedt Subject: Re: [PATCH] rcu: convert rcupreempt trace to seq file Message-ID: <20090111051604.GF7061@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <496852DE.7080802@cn.fujitsu.com> <20090110223151.GD7061@linux.vnet.ibm.com> <20090111013940.GL12885@elte.hu> <20090111050129.GA6131@nowhere> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090111050129.GA6131@nowhere> User-Agent: Mutt/1.5.15+20070412 (2007-04-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jan 11, 2009 at 06:01:31AM +0100, Frederic Weisbecker wrote: > On Sun, Jan 11, 2009 at 02:39:40AM +0100, Ingo Molnar wrote: > > > > * Paul E. McKenney wrote: > > > > > On Sat, Jan 10, 2009 at 03:48:46PM +0800, Li Zefan wrote: > > > > Impact: also fix a bug in show_rcustats() > > > > > > > > Use seq file for simplification, and the global buffer and mutex can be > > > > removed. > > > > > > Looks very good, and passes my tests. > > > > > > > While doing this, I found rcustats will never show 'ggp' and 'rcc' fields > > > > due to a bug in show_rcustats(). > > > > > > Good eyes! > > > > > > The only change I ask is that you pull the contents of > > > rcupreempt_debugfs_init() into the now-one-line rcupreempt_trace_init(). > > > > > > With that change: > > > > > > Tested-by: Paul E. McKenney > > > Reviewed-by: Paul E. McKenney > > > > > > > --- > > > > kernel/rcupreempt_trace.c | 155 ++++++++++++++++++++------------------------- > > > > i think the whole kernel/rcupreempt_trace.c file might be a good candidate > > for the 'statistical tracing' extensions to ftrace that Frederice is > > working on. > > > > That way there would just be a few tracepoints, and the rest would be done > > in kernel/tracing/trace_rcupreempt.c, or so. > > Ingo > > 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. Li Zefan, is this something you would be willing to try? Sounds like it might be a good addition. Thanx, Paul