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Message-ID: <20090130123916.GR627@ghostprotocols.net>
Date: Fri, 30 Jan 2009 10:39:16 -0200
From: Arnaldo Carvalho de Melo <acme@...hat.com>
To: Frederic Weisbecker <fweisbec@...il.com>
Cc: Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...e.hu>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tracing/ftrace: better manage the context info for
events
Em Fri, Jan 30, 2009 at 10:34:46AM -0200, Arnaldo Carvalho de Melo escreveu:
> 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.
Sorry, false alarm, the iterator is there, I was trying to build the
whole binary trace record in the trace_event->bin(), but its not
possible, so I'll do it in two function calls context + trace.
- Arnaldo
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