linux-kernel - Re: [PATCH] gpio: add trace events for setting direction and value

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Message-ID: <1298044086.26768.7242.camel@fedora>
Date:	Fri, 18 Feb 2011 10:48:06 -0500
From:	Steven Rostedt <srostedt@...hat.com>
To:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Cc:	Grant Likely <grant.likely@...retlab.ca>,
	linux-kernel@...r.kernel.org,
	David Brownell <dbrownell@...rs.sourceforge.net>
Subject: Re: [PATCH] gpio: add trace events for setting direction and value

On Fri, 2011-02-18 at 10:58 +0100, Uwe Kleine-König wrote:
> Hi Steven, hi Grant,
> 
> On Wed, Feb 16, 2011 at 12:12:51PM -0500, Steven Rostedt wrote:
> > Note: to save the memory footprint of these tracepoints, you can use
> > DEFINE_EVENT_PRINT(). You can see the usage for this in the
> > include/trace/events/kmem.h.
> > But to do this, you will need to have a single TP_STRUCT__entry() for
> > both. Not sure if this is what you want.
> > 
> > 	TP_STRUCT__entry(
> > 		__field(unsigned, gpiq)
> > 		__field(int, get_in)
> > 		__field(int, value_err)
> > 
> > ??
> > 
> > Just a suggestion, but may not be worth it.
> Yeah, I saw that, still I think it's sane to keep them seperated.
> Or how much would we save?  Can you estimate that?

You can do it :)   Especially since it can vary by archs.

Just compile the kernel once this way, and then try it with
DEFINE_EVENT_PRINT(), compile the kernel and run size on the two.

Then you can see the difference it makes. It may end up not being worth
the difference. But as embedded uses gpio the most, I'll leave that up
to you.

-- Steve



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