linux-kernel - [PATCH perf/core 0/6] perf-probe: Bugfix and add new options for cache

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Date:	Fri, 31 Oct 2014 14:51:29 -0400
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	srikar@...ux.vnet.ibm.com, Peter Zijlstra <peterz@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Brendan Gregg <brendan.gregg@...il.com>,
	yrl.pp-manager.tt@...achi.com, namhyung@...nel.org,
	Hemant Kumar <hemant@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...nel.org>
Subject: [PATCH perf/core 0/6] perf-probe: Bugfix and add new options for
 cache

Hi,

Here is a sereis of patches for enabling "event cache" feature
to perf probe. Brendan gives me this cool idea, thanks! :)

In this series, I added following options/features;
 - --output option
   We can save the probe definition command for given probe-event
   instead of setting up the local tracing/kprobe_events.

 - --no-inlines option
   We can avoid searching the inline functions in debuginfo. Usually
   useful with wildcards since the wildcards will hit a huge amount
   of probe-points.

 - $params special probe argument
   $params is expanded to function parameters only, no locally defined
   variables. This is useful for function-call tracing.

 - wildcard support for function name
   Wildcard support is the key feature for this idea. Now we can use
   '*foo*' for function name to define the probe-point.

So by using all of them, we can make an "event cache" file on all
functions (except for inlined functions) as below.

  # perf probe --max-probes=100000 --no-inlines -a '* $params' -o event.cache

builds "event.cache" file in which event settings for
all function entries, like below;

  p:probe/reset_early_page_tables _text+12980741
  p:probe/copy_bootdata _text+12980830 real_mode_data=%di:u64
  p:probe/exit_amd_microcode _text+14692680
  p:probe/early_make_pgtable _text+12981274 address=%di:u64
  p:probe/x86_64_start_reservations _text+12981700 real_mode_data=%di:u64
  p:probe/x86_64_start_kernel _text+12981744 real_mode_data=%di:u64
  p:probe/reserve_ebda_region _text+12982117

This event.cache file will be big (but much smaller than native
debuginfo :) ) if your kernel have many option embedded.
Anyway, you can compress it too.

  # wc -l event.cache
  33813 event.cache
  # ls -sh event.cache
  2.3M event.cache
  # ls -sh event.cache.gz
  464K event.cache.gz

For setting up a probe event, you can grep the function name
and write it to tracing/kprobe_events, as below;

  # zcat event.cache.gz | \
    grep probe/vfs_symlink > /sys/kernel/debug/tracing/kprobe_events

This can be applied for the remote machine only if the machine
runs on completely same kernel binary. Perhaps, we need some
helper tool to check it.

Thank you,


---

Masami Hiramatsu (6):
      [BUGFIX] perf-probe: Fix to handle optimized not-inlined but has no instance
      [DOC] perf-probe: Update perf-probe document
      perf-probe: Add --output option to write commands in a standard file
      perf-probe: Add --no-inlines option to avoid searching inline functions
      perf-probe: Support $params special probe argument
      perf-probe: Support glob wildcards for function name


 tools/perf/Documentation/perf-probe.txt |   25 ++++++++++
 tools/perf/builtin-probe.c              |   32 +++++++++++++
 tools/perf/util/dwarf-aux.c             |   31 +++++++++++++
 tools/perf/util/dwarf-aux.h             |    6 +++
 tools/perf/util/probe-event.c           |   73 +++++++++++++++++++++++--------
 tools/perf/util/probe-event.h           |    4 +-
 tools/perf/util/probe-finder.c          |   74 +++++++++++++++++++------------
 tools/perf/util/probe-finder.h          |    6 ++-
 tools/perf/util/util.h                  |    4 ++
 9 files changed, 202 insertions(+), 53 deletions(-)

--
Masami HIRAMATSU
Software Platform Research Dpt. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com

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