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

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Date:	Tue, 9 Jun 2015 16:02:15 -0400 (EDT)
From:	Vince Weaver <vincent.weaver@...ne.edu>
To:	David Ahern <dsahern@...il.com>
cc:	Vince Weaver <vincent.weaver@...ne.edu>,
	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>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: perf/ftrace: does PERF_EVENT_IOC_SET_FILTER serve any purpose?

On Tue, 9 Jun 2015, David Ahern wrote:

> On 6/9/15 1:51 PM, Vince Weaver wrote:
> 
> > # 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.
> 
> Do you see this:
> 
> # ls /sys/kernel/debug/tracing/events/irq/irq_handler_entry/
> enable  filter  format  id  trigger
> 
> It's used in kernel/irq/handle.c, handle_irq_event_percpu(). As I recall this
> tracepoint has been around a long time.

# ls /sys/kernel/debug/tracing/events/irq/irq_handler_entry/
enable	filter	format	id  trigger

# perf list
....
  [ Tracepoints not available: No such file or directory ]

strace shows
statfs("/sys/kernel/debug/tracing/events", {f_type=0x74726163, 
f_bsize=4096, f_blocks=0, f_bfree=0, f_bavail=0, f_files=0, f_ffree=0, 
f_fsid={0, 0}, f_namelen=255, f_frsize=4096}) = 0

so I have no idea what's going wrong here.


Anyway, on a related question, I see for the event that you use
	--filter irq==28
How do I find out the valid filters for each event?  Do I have to parse
the "format" file under
	/sys/kernel/debug/tracing/events/*/* ?

Vince
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