linux-kernel - printk instrumentation with LTTng

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Message-ID: <20060917193500.GA10332@Krystal>
Date:	Sun, 17 Sep 2006 15:35:01 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Andrew Morton <akpm@...l.org>, tglx@...utronix.de,
	karim@...rsys.com, Paul Mundt <lethal@...ux-sh.org>,
	Jes Sorensen <jes@....com>,
	Roman Zippel <zippel@...ux-m68k.org>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Christoph Hellwig <hch@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Tom Zanussi <zanussi@...ibm.com>, ltt-dev@...fik.org,
	Michel Dagenais <michel.dagenais@...ymtl.ca>
Subject: printk instrumentation with LTTng

* Alan Cox (alan@...rguk.ukuu.org.uk) wrote:
> In addition ideally we want a mechanism that is also sufficient that
> printk can be mangled into so that you can pull all the printk text
> strings _out_ of the kernel and into the debug traces for embedded work.
> 

Further on, in LTTng 0.5.113, I added the possibility to trace the location
where the printk happened. Within a huge amount of information, this kind of
data identification can be very useful.

Example of a printk as shown from the text dump of a trace :

kernel.printk_locate: 181.713815470 (/tmp/trace2/cpu_0),
  4357, 0, insmod, UNBRANDED, 4234, 0x0, SYSCALL,
  { file = "/home/compudj/repository/tests/kernel/test-printk.c",
    function = "init_module", line = 14, address = 0xf88eb000 }

kernel.printk: 181.713817590 (/tmp/trace2/cpu_0),
  4357, 0, insmod, UNBRANDED, 4234, 0x0, SYSCALL,
  { loglevel = 0, text = { printk message } }

Regards,


Mathieu



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