Re: [PATCH 2/4] ftrace - add function_duration tracer

[Steven Rostedt <rostedt@goodmis.org>]

On Thu, 2009-12-10 at 13:03 +0100, Frederic Weisbecker wrote:

> This makes me feel I'm going to try converting the function graph tracer
> into an event during the next cycle. It does not mean I could make it
> usable as a perf event right away in the same shot that said, as you can
> guess this is not a trivial plug. The current perf fast path is not yet
> adapted for that.

I curious how you plan on doing this. The current event system shows one
event per trace point. A straight forward approach would make every
entry and exit of a function a trace point and that would lead to a very
large kernel to handle that.

Perhaps we could abstract out all entries and exits. We need to be able
to link to a single point (entry or exit) not all.  This also has the
added issue of using the ftrace infrastructure of nop the mcount call.
We also need a way to enable a set of functions.

We may be able to abstract this out, but I'm hesitant on making this the
only interface.

-- Steve