Re: [RFC 3/4] perf, ftrace: Add new perf ioctl for function tracefilter

From: Frederic Weisbecker
Date: Mon Jul 18 2011 - 11:12:46 EST

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

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

ip == !func1
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