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From: Ingo Molnar <>
To: Steven Rostedt <>
Cc: "Frédéric Weisbecker" <>,
Subject: Re: [RFC][PATCH] Make ftrace able to trace function return
Date: Thu, 30 Oct 2008 20:26:21 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

* Steven Rostedt <> wrote:

> gcc -c -finstrument-functions traceme.c

> This is not 5 extra bytes but 27 extra bytes for a total of 32 bytes 
> at every function. Also note that this also adds these calls to 
> inline functions as well. We could easly stop that by adding 
> "notrace" to the inline define (which I've done).
> But this would make the patching a bit more difficult (not 
> impossible). But it will bloat the image quite a bit.

yeah, i too knew it was expensive, but didnt realize it's this bloaty. 
It's a non-starter really.

How reliable can we make Frederic's trampoline approach? Especially 
with the opt-in function filters of dyn-ftrace, there's real value in 
the trampoline approach IMO (we could display real function cost, 
etc.), and the runtime cost should be OK as long we dont probe a ton 
of functions all the time. (and it's optional anyway)


  reply	other threads:[~2008-10-30 19:26 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-10-30 19:20 Frederic Weisbecker
2008-10-30 18:20 ` Ingo Molnar
2008-10-30 18:30   ` Frédéric Weisbecker
2008-10-30 18:37     ` Ingo Molnar
2008-10-30 19:17       ` Steven Rostedt
2008-10-30 19:26         ` Ingo Molnar [this message]
2008-11-03 11:16           ` Ananth N Mavinakayanahalli
2008-11-03 13:32             ` Frédéric Weisbecker
2008-10-31  1:35       ` Frédéric Weisbecker
2008-10-30 20:30 ` Steven Rostedt
2008-10-31  0:05   ` Frédéric Weisbecker
2008-10-31  2:43     ` Steven Rostedt
2008-10-31 20:18       ` Frederic Weisbecker
2008-11-03 10:06         ` Ingo Molnar
2008-11-03 13:11           ` Frédéric Weisbecker

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