linux-kernel - Re: [PATCH 09/14] perf ftrace: Add 'record' sub-command

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Date:	Wed, 24 Apr 2013 16:12:41 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	David Ahern <dsahern@...il.com>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 09/14] perf ftrace: Add 'record' sub-command

On Tue, Apr 23, 2013 at 05:31:07PM +0900, Namhyung Kim wrote:
> From: Namhyung Kim <namhyung.kim@....com>
> 
> The ftrace record command is for saving raw ftrace buffer contents
> which can be get from per_cpu/cpuX/trace_pipe_raw.
> 
> Since ftrace events are generated very frequently so single thread for
> recording mostly resulted in buffer overruns.  Thus it uses per-cpu
> recorder thread to prevent such cases and they save the contents to
> their own files.
> 
> These per-cpu data files are saved in a directory so that they can be
> easily found when needed.  I chose the default directory name as
> "perf.data.dir" and the first two (i.e. "perf.data") can be changed
> with -o option.  The structure of the directory looks like:
> 
>   $ tree perf.data.dir
>   perf.data.dir/
>   |-- perf.header
>   |-- trace-cpu0.buf
>   |-- trace-cpu1.buf
>   |-- trace-cpu2.buf
>   `-- trace-cpu3.buf
> 
> In addition to trace-cpuX.buf files, it has perf.header file also.
> The perf.header file is compatible with existing perf.data format and
> contains usual event information, feature mask and sample data.  The
> sample data is synthesized to indicate given cpu has a record file.

I got following lockup for record command:

  # ./perf --no-pager ftrace record ls
  ...
  hangs

  in other terminal:

  # pstack 14237
  Thread 2 (Thread 0x7f3f1aa1d700 (LWP 14241)):
  #0  0x0000003cec20b595 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
  #1  0x0000000000446ebe in record_ftrace_raw_buffer (arg=0x21f9ce0) at builtin-ftrace.c:451
  #2  0x0000003cec207d14 in start_thread () from /lib64/libpthread.so.0
  #3  0x0000003cebaf168d in clone () from /lib64/libc.so.6
  Thread 1 (Thread 0x7f3f1ba209c0 (LWP 14237)):
  #0  0x0000003cec208e60 in pthread_join () from /lib64/libpthread.so.0
  #1  0x0000000000449c8c in do_ftrace_record (ftrace=ftrace@...ry=0x7fff1377d240) at builtin-ftrace.c:682
  #2  0x000000000044a57b in __cmd_ftrace_record (argv=0x7fff1377d818, argc=<optimized out>, ftrace=0x7fff1377d240) at builtin-ftrace.c:1535
  #3  cmd_ftrace (argc=2, argv=0x7fff1377d818, prefix=<optimized out>) at builtin-ftrace.c:1655
  #4  0x000000000041a763 in run_builtin (p=p@...ry=0x7d58a0, argc=argc@...ry=3, argv=argv@...ry=0x7fff1377d818) at perf.c:320
  #5  0x0000000000419faf in handle_internal_command (argv=0x7fff1377d818, argc=3) at perf.c:377
  #6  run_argv (argv=0x7fff1377d600, argcp=0x7fff1377d60c) at perf.c:421
  #7  main (argc=3, argv=0x7fff1377d818) at perf.c:522

jirka
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