linux-kernel - Re: [RFC 3/4] perf, ftrace: Add new perf ioctl for function trace filter

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Message-ID: <20110718151229.GA32167@somewhere>
Date:	Mon, 18 Jul 2011 17:12:33 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	rostedt@...dmis.org, a.p.zijlstra@...llo.nl,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>
Subject: Re: [RFC 3/4] perf, ftrace: Add new perf ioctl for function trace
 filter

On Mon, Jul 11, 2011 at 03:22:55PM +0200, Jiri Olsa wrote:
> As the amount of kernel functions obtained by the ftrace:function tracepoint
> is quite big, it's desirable to be able to set the filter on the ftrace
> level.
> 
> Added PERF_EVENT_IOC_SET_FTRACE ioctl to be able to specify function filter
> for perf event. The interface is the same as for the set_ftrace_filter file.
> 
> Also the same string parser is used as for the set_ftrace_filter file.

I'm not sure I understand why an ioctl is needed for that.
Why not using the ftrace filter?

The first idea was to do something like this:

	ip == func1 || ip == func2 || ....

But that makes a too long expression. So I thought we
could bring support for the "+" operator and have expressions
like:

	ip == func1 + func2 + func3 + ....

	ip == !func1
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