From: Axel Rasmussen <axelrasmussen@google.com>
To: Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Michel Lespinasse <walken@google.com>,
Vlastimil Babka <vbabka@suse.cz>,
Daniel Jordan <daniel.m.jordan@oracle.com>,
Jann Horn <jannh@google.com>,
Chinwen Chang <chinwen.chang@mediatek.com>,
Davidlohr Bueso <dbueso@suse.de>,
David Rientjes <rientjes@google.com>
Cc: Yafang Shao <laoar.shao@gmail.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Axel Rasmussen <axelrasmussen@google.com>
Subject: [PATCH v4 0/1] Add tracepoints around mmap_lock acquisition
Date: Tue, 20 Oct 2020 11:47:45 -0700 [thread overview]
Message-ID: <20201020184746.300555-1-axelrasmussen@google.com> (raw)
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 v3:
- Switched EXPORT_SYMBOL to EXPORT_TRACEPOINT_SYMBOL, removed comment.
- Removed redundant trace_..._enabled() check.
- Defined the three TRACE_EVENTs separately, instead of sharing an event class.
The tradeoff is 524 more bytes in .text, but the start_locking and released
events no longer have a vestigial "success" field, so they're simpler +
faster.
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 (1):
mmap_lock: add tracepoints around lock acquisition
include/linux/mmap_lock.h | 93 ++++++++++++++++++++++++++++--
include/trace/events/mmap_lock.h | 98 ++++++++++++++++++++++++++++++++
mm/Makefile | 2 +-
mm/mmap_lock.c | 80 ++++++++++++++++++++++++++
4 files changed, 267 insertions(+), 6 deletions(-)
create mode 100644 include/trace/events/mmap_lock.h
create mode 100644 mm/mmap_lock.c
--
2.29.0.rc1.297.gfa9743e501-goog
next reply other threads:[~2020-10-20 18:47 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-20 18:47 Axel Rasmussen [this message]
2020-10-20 18:47 ` [PATCH v4 0/1] Add tracepoints around mmap_lock acquisition Axel Rasmussen
2020-10-20 18:47 ` [PATCH v4 1/1] mmap_lock: add tracepoints around lock acquisition Axel Rasmussen
2020-10-20 18:47 ` Axel Rasmussen
2020-10-23 13:59 ` Vlastimil Babka
2020-10-23 17:38 ` Axel Rasmussen
2020-10-23 17:38 ` Axel Rasmussen
2020-10-23 17:56 ` Vlastimil Babka
2020-10-26 14:54 ` Steven Rostedt
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