[PATCH v4 0/7] perf/sdt: Directly record SDT events with 'perf record'

[Ravi Bangoria]

All events from 'perf list', except SDT events, can be directly recorded
with 'perf record'. But, the flow is little different for SDT events.
Probe point for SDT event needs to be created using 'perf probe' before
recording it using 'perf record'.

As suggested by Ingo[1], it's better to make this process simple by
creating probe point automatically with 'perf record' for SDT events.

Features:
  - Allow both 'perf probe' and 'perf record' on sdt events without
    changing current functionality.

  - Event starting with 'sdt_' or '%' will be considered as SDT event.

  - Always prioritize events from uprobe_events by first checking if
    event exists with exact name. If not found and user has used
    pattern, again try to find pattern matching entries from
    uprobe_events. If found use them. If not, lookup into probe-cache.
    If events found from probe-cache, again check if any event exists
    in uprobe_events by matching filepath+address, as it might exists
    in uprobe_events but with different name. Reuse those events which
    exists in uprobe_events and create new entries for missing one.
    Also maintain list for new entries being created and at the end
    of the session, delete them.

  - Show various warnings/hints to help user understand _which_ events
    are being recorded and _why_. For ex,

    When multiple events of same name found and all are being recorded:

      $ sudo ./perf record -a -e sdt_libpthread:mutex_entry
        Warning: Recording on 2 occurrences of sdt_libpthread:mutex_entry

    Events being reused from uprobe_events is listed as 'name addr@file'
    followed by hint on how to delete them:

      $ sudo ./perf record -a -e sdt_libpthread:mutex_entry
        Matching event(s) from uprobe_events:
          sdt_libpthread:mutex_entry  0x9ddb@/usr/lib64/libpthread-2.24.so
        Use 'perf probe -d <event>' to delete event(s).

    If number of events found from cache is not equal to number of events
    being recorded:

      $ sudo ./perf record -a -e sdt_libpthread:mutex_entry
        Warning: Found 2 events from probe-cache with name 'sdt_libpthread:mutex_entry'.
                 Since 1 probe point already exists, recording only it.
        Hint: Please use 'perf probe -d sdt_libpthread:mutex_entry' to allow record on all events.

Changes in v4:
  - Moved util function is_sdt_event() from tools/perf/util/util.c to
    tools/perf/util/parse-events.h. [PATCH 1/7]

  - Split hunk into multiple patches.

  - Changed pr_err() to pr_debug() (only where Masami has suggested).

  - Removed unnecessary wrapper func find_sdt_events_from_cache() by
    exposing find_cached_events_all().

  - Removed 'struct exst_sdt_event_list', instead using array of
    existing data structure 'struct probe_trace_event'.

  - No hint will be shown at 'perf probe' for SDT events.

  - Functionality change. If all events found from probe-cache are not
    present in uprobe_events, v3 was recording all events found from
    cache. That has been changed in v4. If user has used pattern to
    specify event, v4 will record only those events which are present
    in uprobe_events. This is to make perf semantics consistent across
    normal and SDT events. And If user has not used pattern, it will
    record all events found from probe-cache by reusing name for
    existing one and adding entries for missing one. For ex (with v4),
    
      $ sudo ./perf probe sdt_libpthread:mutex_release
        Added new events:
          sdt_libpthread:mutex_release (on %mutex_release in /usr/lib64/libpthread-2.24.so)
          sdt_libpthread:mutex_release_1 (on %mutex_release in /usr/lib64/libpthread-2.24.so)
          sdt_libpthread:mutex_release_2 (on %mutex_release in /usr/lib64/libpthread-2.24.so)
          sdt_libpthread:mutex_release_3 (on %mutex_release in /usr/lib64/libpthread-2.24.so)
      $ sudo ./perf probe -d sdt_libpthread:mutex_release
      $ sudo ./perf probe -d sdt_libpthread:mutex_release_2

      $ sudo ./perf record -a -e sdt_libpthread:mutex_release*
        Warning: Recording on 2 occurrences of sdt_libpthread:mutex_release*

      $ sudo ./perf record -a -e sdt_libpthread:mutex_release
        Warning: Recording on 4 occurrences of sdt_libpthread:mutex_release


This patchset is prepared on top of acme/perf/core.

v3 link: https://lkml.org/lkml/2017/2/24/27

[1] https://lkml.org/lkml/2017/2/7/59
[2] https://lkml.org/lkml/2016/5/3/810


Hemant Kumar (1):
  perf/sdt: Directly record SDT events with 'perf record'

Ravi Bangoria (6):
  perf/sdt: Introduce util func is_sdt_event()
  perf/sdt: Allow recording of existing events
  perf/sdt: Clean uprobe_events when event(out of multiple events)
    parsing fails
  perf/sdt: Warn when number of events recorded are not equal to cached
    events
  perf/sdt: List events fetched from uprobe_events
  perf/sdt: Remove stale warning

 tools/lib/api/fs/tracing_path.c |  17 +--
 tools/perf/builtin-record.c     |  23 +++
 tools/perf/perf.h               |   2 +
 tools/perf/util/parse-events.c  |  56 +++++++-
 tools/perf/util/parse-events.h  |  14 ++
 tools/perf/util/probe-event.c   | 100 +++++++++++--
 tools/perf/util/probe-event.h   |   9 ++
 tools/perf/util/probe-file.c    | 310 ++++++++++++++++++++++++++++++++++++++++
 tools/perf/util/probe-file.h    |   9 ++
 9 files changed, 513 insertions(+), 27 deletions(-)

-- 
2.9.3