linux-kernel - Re: [PATCH 3/5] ftrace perf: Use ftrace

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Date:	Fri, 18 Mar 2016 10:28:44 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Jiri Olsa <jolsa@...nel.org>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: [PATCH 3/5] ftrace perf: Use ftrace_ops::private to store event
 pointer

On Wed, 16 Mar 2016 15:34:31 +0100
Jiri Olsa <jolsa@...nel.org> wrote:

> Having following commands running concurrently:
> 
>   # perf record -e ftrace:function -a -o krava.data sleep 10
>   # perf record -e ftrace:function --filter 'ip == SyS_read' ls
> 
> will end up in the latter one to fail on the filter rules
> and store all functions (in perf.data) as instructed by the
> first perf record instead of just SyS_read records.
> 
> The reason for this is, that tracepoint code by default
> triggers all events that registered for the tracepoint.
> 
> While ftrace:function is special because ftrace_ops
> itself carries a filter and only the event that owns
> ftrace_ops is eligible to be triggered.
> 
> Fixing this by using ftrace_ops::private value to keep
> the perf_event pointer. This way we don't need to search
> for triggered event (as tracepoint handler does) and
> directly store sample.
> 
> Acked-by: Namhyung Kim <namhyung@...nel.org>
> Suggested-by: Steven Rostedt <rostedt@...dmis.org>
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>

Acked-by: Steven Rostedt <rostedt@...dmis.org>

-- Steve