Re: [PATCH 1/2] ftrace: Add separate handler for ftrace:function event

[Steven Rostedt]

On Wed, 25 Nov 2015 16:45:32 +0100
Jiri Olsa <jolsa@xxxxxxxxxx> wrote:

> Having following commands running concurently:
> 
>   # perf record -e ftrace:function -a -o krava.data sleep 10
>   # perf record -e ftrace:function --filter 'ip == SyS_read' ls
> 
> will endup in the latter one failing on the filter
> rules and store all functions (in perf.data) as
> instructed by the first record instead of just
> SyS_read records.
> 
> The reason is that we don't check the ftrace_ops that
> triggered the event with event's ftrace_ops. Hence
> once running together the event from latter perf will
> get all the data of the event from the first one.
> 
> Fixing this by having separate handler for ftrace:function
> event that actualy checks ftrace_ops against event.

This seems redundant. I never understood the control_ops that perf uses
in the function tracing infrastructure. Why can't you just register the
event->ops and have that ops set the filtering? Then the ftrace
infrastructure will only call that event handler for the functions its
filtered on. Then you don't need to do it again. Right now ftrace
already does that with the generic "control_ops" that perf uses, but
now you are doing it again. Seems rather pointless.

I may need to spend some time looking at how perf uses the function
tracing, and perhaps we can remove a lot of this redundancy.

-- Steve

> 
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
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