linux-kernel - Re: [PATCH] tracing/function-graph-tracer: adjustments of the trace informations

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Date:	Sat, 29 Nov 2008 04:24:14 +0100
From:	"Frédéric Weisbecker" <fweisbec@...il.com>
To:	"Ingo Molnar" <mingo@...e.hu>
Cc:	"Steven Rostedt" <rostedt@...dmis.org>,
	"Tim Bird" <tim.bird@...sony.com>,
	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
	"Linux Kernel" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tracing/function-graph-tracer: adjustments of the trace informations

2008/11/28 Ingo Molnar <mingo@...e.hu>:
> Yeah, that needs updating. I supposed you'd be working on the task+pid
> column anyway, and do a helper function that prints the task-pid couple.
> Then that helper can be used in the context-switch case too to print out
> a uniform ID.


Ok.



> Another thing that would be nice is to separate out the "cpu)" printing
> bits into a helper function. Right now what exists cannot be used in a
> seq-manner, so i couldnt reuse it.
>


Isn't it the case with print_graph_cpu() ?

> Anyway, i wont change it (just wanted to get a final-ish output to look
> at) so feel free to clean it all up thoroughly :)
>
> Today i played with the graph-tracer on a testbox _way_ too much.
> Combined with the wildcard filter it's _really_ addictive. Kernel
> developers, beware!


:-)


>
> One thing that came up: it would be nice to have an 'inverted' wildcard
> to punch out certain functions from the filter list. For example i did in
> the shell:
>
>  $ echo 'sys_*'    >> set_ftrace_filter
>  $ echo '*socket*' >> set_ftrace_filter
>  $ echo '*timer*'  >> set_ftrace_filter
>  $ echo '*skb*'    >> set_ftrace_filter
>
> and looked at the trace and found that certain functions are too verbose
> and not really interesting - so i wanted to exclude them.
>
> We've got set_ftrace_notrace but it's not really an inverse wildcard but
> a complementary set of filter functions - which is not the same and not
> as easy to think about as a single set of filter functions.
>
> what i think would be more natural to do is via the filter file itself,
> via an extension like:
>
>  $ echo '!timer_*' >> set_ftrace_filter
>
> which would eliminate the functions matching that negative pattern. Such
> negative wildcards would act on the current set of functions, while
> set_ftrace_notrace is permanent and cannot be used to shape an arbitrary
> set of functions iteratively.


Ok, I'll add it in my workqueue (unless Steven does it).
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