Return-Path: <linux-kernel-owner+w=401wt.eu-S1753940AbZA3Mf0@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1753940AbZA3Mf0 (ORCPT <rfc822;w@1wt.eu>);
	Fri, 30 Jan 2009 07:35:26 -0500
Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751100AbZA3MfM
	(ORCPT <rfc822;linux-kernel-outgoing>);
	Fri, 30 Jan 2009 07:35:12 -0500
Received: from mx2.redhat.com ([66.187.237.31]:37611 "EHLO mx2.redhat.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1751376AbZA3MfL (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Fri, 30 Jan 2009 07:35:11 -0500
Date: Fri, 30 Jan 2009 10:34:46 -0200
From: Arnaldo Carvalho de Melo <acme@redhat.com>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>, Ingo Molnar <mingo@elte.hu>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] tracing/ftrace: better manage the context info for
	events
Message-ID: <20090130123446.GQ627@ghostprotocols.net>
Mail-Followup-To: Arnaldo Carvalho de Melo <acme@redhat.com>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>, Ingo Molnar <mingo@elte.hu>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
References: <4982c159.190c660a.7424.ffffabf9@mx.google.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <4982c159.190c660a.7424.ffffabf9@mx.google.com>
X-Url: http://oops.ghostprotocols.net:81/blog
User-Agent: Mutt/1.5.18 (2008-05-17)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 2128
Lines: 48

Em Fri, Jan 30, 2009 at 12:59:05AM -0800, Frederic Weisbecker escreveu:
> Impact: make trace_event more convenient for tracers
> 
> All tracers (for the moment) that use the struct trace_event want to have
> the context info printed before their own output: the pid/cmdline, cpu, and timestamp.
> 
> But some other tracers that want to implement their trace_event callbacks will
> not necessary need these information or they may want to format them as they want.
> 
> This patch adds a new default-enabled trace option: TRACE_ITER_CONTEXT_INFO
> When disabled through:
> 
> echo nocontext-info > /debugfs/tracing/trace_options
> 
> The pid, cpu and timestamps headers will not be printed.
> 
> IE with the sched_switch tracer with context-info (default):
> 
>             bash-2935  [001]   100.356561:   2935:120:S ==> [001]     0:140:R <idle>
>           <idle>-0     [000]   100.412804:      0:140:R   + [000]    11:115:S events/0
>           <idle>-0     [000]   100.412816:      0:140:R ==> [000]    11:115:R events/0
>         events/0-11    [000]   100.412829:     11:115:S ==> [000]     0:140:R <idle>
> 
> Without context-info:
> 
>   2935:120:S ==> [001]     0:140:R <idle>
>      0:140:R   + [000]    11:115:S events/0
>      0:140:R ==> [000]    11:115:R events/0
>     11:115:S ==> [000]     0:140:R <idle>
> 
> A tracer can disable it at runtime by clearing the bit TRACE_ITER_CONTEXT_INFO in trace_flags.
> 
> Moreover, two callbacks have been added inside trace_event:
> _ context_info() which let a tracer override the format of the context info
> _ lat_context_info() which do the same with the latency_trace file
> 
> If they are not defined, the usual way of printing the context info will be used.

Please wait a bit, I'm trying to use it and the first thing I notice was
that I need the trace_iterator in the context callback, to get the
timestamp.

- Arnaldo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/