linux-kernel - Re: perf events over (net) console?

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Date:	Thu, 9 Sep 2010 11:41:06 -0300
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	Harald Gustafsson <hgu1972@...il.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Harald Gustafsson <hgu1972@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Harald Gustafsson <harald.gustafsson@...csson.com>,
	Song Yuan <song.yuan@...csson.com>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: perf events over (net) console?

Em Thu, Sep 09, 2010 at 03:21:00PM +0200, Frederic Weisbecker escreveu:
> In the beginning this could wrap into perf record - | perf pipe | netcat
> and so, until we get the splice support.

Isn't this what Tom Zanussi's live mode, that we have already special
casing 'perf record -' does?

Look at these tools/perf/builtin-record.c excerpts:

static int __cmd_record(int argc, const char **argv)
{
<SNIP>
        if (!strcmp(output_name, "-"))
                pipe_output = 1;
<SNIP>
        if (pipe_output)
                output = STDOUT_FILENO;
        else
                output = open(output_name, flags, S_IRUSR | S_IWUSR);
<SNIP>
	if (pipe_output) {
                err = perf_header__write_pipe(output);
<SNIP>
        if (pipe_output) {
                err = event__synthesize_attrs(&session->header,
                                              process_synthesized_event,
                                              session)
<SNIP>
}

Harald, can you please take a look at the comment for these commits:

commit 454c407ec17a0c63e4023ac0877d687945a7df4a
Author: Tom Zanussi <tzanussi@...il.com>
Date:   Sat May 1 01:41:20 2010 -0500

    perf: add perf-inject builtin

commit 529870e37473a9fc609078f03cc5b4148cf06a87
Author: Tom Zanussi <tzanussi@...il.com>
Date:   Thu Apr 1 23:59:16 2010 -0500

    perf record: Introduce special handling for pipe output

commit 8dc58101f2c838355d44402aa77646649d10dbec
Author: Tom Zanussi <tzanussi@...il.com>
Date:   Thu Apr 1 23:59:15 2010 -0500

    perf: Add pipe-specific header read/write and event processing code

Using live mode you can stream to a perf.data for later analisys or do
it live, piping it to trace scripts, etc.

Doing it using splice, talking directly to an in kernel mini-server, etc
are all optimizations that we should think about, but if you can try
using the live mode and see if it is ok, that would be good.

A mini binary with just record can come in handy if you like and should
be rather easy to build, please let me know if you think it is a good
idea and if you need help, lemme know.

- Arnaldo
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