linux-kernel - Re: FW: [RFC 0/5] perf tools: Add perf data CTF conversion

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Date:	Thu, 21 Aug 2014 18:58:41 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Alexandre Montplaisir <alexmonthy@...populi.im>
Cc:	linux-kernel@...r.kernel.org,
	Dominique Toupin <dominique.toupin@...csson.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Tom Zanussi <tzanussi@...il.com>,
	Jeremie Galarneau <jgalar@...icios.com>,
	David Ahern <dsahern@...il.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: FW: [RFC 0/5] perf tools: Add perf data CTF conversion

On Wed, Aug 20, 2014 at 03:14:20PM -0400, Alexandre Montplaisir wrote:
> On 08/20/2014 05:28 AM, Jiri Olsa wrote:
> >
> >ok, easy enough ;-) so I'm guessing this governs the expected
> >CTF layout for event/stream headers/contexts, right?
> 
> Correct, if the domain is "kernel" we then assume that the rest of the trace
> contains the expected elements of a kernel trace.
> 
> Of course, one could craft a CTF trace to advertize itself as "kernel" or
> "ust", and not actually have the layout of that trace type, in which case it
> would fail parsing later on.
> 
> >Also judging from the trace display, you have hardcoded specific
> >displays/actions for specific events? That's all connected/specific
> >under trace type?
> 
> Yes the trace type is the main "provider" of functionality. I could go into
> more details, but we use Eclipse extension points to define which columns to
> put in the event table, which views are available, etc. for each supported
> trace type.
> 
> >>Once we have some views or analysis specific to perf CTF traces, we could
> >>definitely add a separate trace type for those too.
> >I guess tracepoints and breakpoints should display something like
> >the standard kernel trace. As for HW events it's usual to display
> >profile infomation as the perf report does:
> >   https://perf.wiki.kernel.org/index.php/Tutorial#Sampling_with_perf_record
> 
> Interesting, I haven't tried the perf CTF output yet, but I could see it
> using the Statistics view (which by default just prints the % of events, per
> event type) to print the results of the different "perf reports", calculated
> from the CTF events. Eventually with pie charts!

Basically, perf monitors single HW event and reports its hits/samples
distribution across the workload processes.

Just by running:
  $ perf record ls ; perf report

you'll get report of HW event 'cycles' distribution over/during the
ls process life:

Samples: 29  of event 'cycles', Event count (approx.): 3763985
   9.65%  ls  [kernel.kallsyms]  [k] find_get_page
   5.09%  ls  [kernel.kallsyms]  [k] perf_event_context_sched_in
   5.09%  ls  ls                 [.] calculate_columns
   5.08%  ls  [kernel.kallsyms]  [k] tty_insert_flip_string_fixed_flag
   5.07%  ls  libc-2.17.so       [.] get_next_seq
   5.06%  ls  [kernel.kallsyms]  [k] down_read_trylock
   5.04%  ls  ls                 [.] xstrcoll_name
   5.03%  ls  libc-2.17.so       [.] __memmove_sse2
   5.03%  ls  libc-2.17.so       [.] _dl_addr
   5.00%  ls  [kernel.kallsyms]  [k] ext4_release_file
   4.99%  ls  [kernel.kallsyms]  [k] filemap_fault
   4.88%  ls  ld-2.17.so         [.] _dl_map_object_from_fd

> 
> >I tried to record/display lttng event perf:cpu:cycles, but got nothing
> >displayed in eclipse. Looks like this data provides only summary count
> >of the event for the workload?
> 
> Just to be sure I understand, you recorded an LTTng kernel trace, in which
> you enabled the "perf:cpu:cycles" context? Did this trace display anything
> in Babeltrace?
> It should display the same in the Eclipse viewer, the value of the context
> will be visible in the "Contents" column in the the table (and in the
> Properties view), although for now we don't make any use of it.

hum, I've got nothing from babeltrace:

[jolsa@...va ~]$ su
Password: 
[root@...va jolsa]# lttng create perf
Spawning a session daemon
Session perf created.
Traces will be written in /root/lttng-traces/perf-20140821-184956
[root@...va jolsa]# lttng add-context -k -t prio -t perf:cpu:cycles
kernel context prio added to all channels
kernel context perf:cpu:cycles added to all channels
[root@...va jolsa]# lttng start
Tracing started for session perf
[root@...va jolsa]# lttng stop
Waiting for data availability.
Tracing stopped for session perf
[root@...va jolsa]# lttng destroy
Session perf destroyed
[root@...va jolsa]# babeltrace ~/lttng-traces/perf-20140821-184956/
[root@...va jolsa]# babeltrace ~/lttng-traces/perf-20140821-184956/kernel/
[root@...va jolsa]#

and empty view in eclipse

thanks,
jirka
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