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

[Ingo Molnar <mingo@elte.hu>]

* Tim Bird <tim.bird@am.sony.com> wrote:

> Add function duration tracer.
> 
> Signed-off-by: Tim Bird <tim.bird@am.sony.com>
> ---
>  kernel/trace/Kconfig          |    8
>  kernel/trace/Makefile         |    1
>  kernel/trace/trace.c          |   32 ++
>  kernel/trace/trace_duration.c |  527 ++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 568 insertions(+)

Please do it in a cleaner an more generic fashion: add a "function 
event" that perf can see and process, so all the output embellishment 
can be done outside of the kernel, in tools/perf/.

We want to wind down the current maze of ftrace plugins, not extend 
them. We already obsoleted the following ftrace plugins: scheduler, 
sysprof, blktrace, kmem, scheduler, etc. There's more work ongoing and 
broad agreement between folks developing it that this is the way 
forward.

The function tracer / function graph tracer is a holdout due to its 
complexity - but that by no means weakens the argument and the necessity 
to migrate it.

ftrace plugins were a nice idea originally and a clear improvement over 
existing alternatives, but now that we've got a technicaly superior, 
unified event framework that can do what the old plugins did and much 
more, we want to improve that and not look back ...

Thanks,

	ingo