[v3,0/2] Add tracepoints around mmap_lock acquisition

Message

Axel Rasmussen Oct. 9, 2020, 10:05 p.m. UTC

This patchset adds tracepoints around mmap_lock acquisition. This is useful so
we can measure the latency of lock acquisition, in order to detect contention.

This version is based upon linux-next (since it depends on some recently-merged
patches [1] [2]).

Changes since v2:

- Refactored tracing helper functions so the helpers are simper, but the locking
  functinos are slightly more verbose. Overall, this decreased the delta to
  mmap_lock.h slightly.

- Fixed a typo in a comment. :)

Changes since v1:

- Functions renamed to reserve the "trace_" prefix for actual tracepoints.

- We no longer measure the duration directly. Instead, users are expected to
  construct a synthetic event which computes the interval between "start
  locking" and "acquire returned".

- The new helper for checking if tracepoints are enabled in a header is used to
  avoid un-inlining any of the lock wrappers. This yields ~zero overhead if the
  tracepoints aren't enabled, and therefore obviates the need for a Kconfig for
  this change.

[1] https://lore.kernel.org/patchwork/patch/1316922/
[2] https://lore.kernel.org/patchwork/patch/1311996/

Axel Rasmussen (2):
  tracing: support "bool" type in synthetic trace events
  mmap_lock: add tracepoints around lock acquisition

 include/linux/mmap_lock.h         | 93 +++++++++++++++++++++++++++++--
 include/trace/events/mmap_lock.h  | 70 +++++++++++++++++++++++
 kernel/trace/trace_events_synth.c |  4 ++
 mm/Makefile                       |  2 +-
 mm/mmap_lock.c                    | 87 +++++++++++++++++++++++++++++
 5 files changed, 250 insertions(+), 6 deletions(-)
 create mode 100644 include/trace/events/mmap_lock.h
 create mode 100644 mm/mmap_lock.c

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2.28.0.1011.ga647a8990f-goog