linux-kernel - Re: perf/ftrace: does PERF_EVENT_IOC_SET

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Message-ID: <20150609155506.3c7d5fc3@gandalf.local.home>
Date:	Tue, 9 Jun 2015 15:55:06 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Vince Weaver <vincent.weaver@...ne.edu>
Cc:	David Ahern <dsahern@...il.com>, linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Stephane Eranian <eranian@...il.com>,
	Jiri Olsa <jolsa@...hat.com>
Subject: Re: perf/ftrace: does PERF_EVENT_IOC_SET_FILTER serve any purpose?

On Tue, 9 Jun 2015 15:51:53 -0400 (EDT)
Vince Weaver <vincent.weaver@...ne.edu> wrote:

> On Tue, 9 Jun 2015, David Ahern wrote:
> 
> > On 6/9/15 12:30 PM, Vince Weaver wrote:
> > > Hello
> > > 
> > > I've been working on documenting the PERF_EVENT_IOC_SET_FILTER ioctl.
> > > 
> > > I've been trying for the past 2 days and have been unable to get any
> > > result except EINVAL.
> > > 
> > > Does anyone ever use this ioctl?  Does anyone know how to use this ioctl?
> > 
> > yes and yes it works.
> > 
> > perf record -e irq:irq_handler_entry --filter irq==28 \
> >             -e irq:softirq_entry --filter vec==6 -a \
> >      -- sleep 5
> 
> # perf record -e irq:irq_handler_entry --filter irq==28 -e irq:softirq_entry --filter vec==6 -a -- sleep 5 
> invalid or unsupported event: 'irq:irq_handler_entry'
> Run 'perf list' for a list of valid events
> 
> perf list doesn't show any tracepoint events, despite having debugfs 
> mounted and running as root and /sys/kernel/debug/tracing/events/ being
> populated.
> 

What kernel are you using? You may need to update perf.

We switched to a tracefs filesystem, but the old perf wont read any
events if it's not located in debugfs. That is, it actually tested
which filesystem the event files were mounted on, and if they didn't
match the debugfs mount type, it ignored them. That was fixed recently.

-- Steve
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