[v6,0/4] Tracing contention lock owner call stack

Message

Chun-Tse Shao Feb. 19, 2025, 9:39 p.m. UTC

For perf lock contention, the current owner tracking (-o option) only
works with per-thread mode (-t option). Enabling call stack mode for
owner can be useful for diagnosing why a system running slow in
lock contention.

Example output:
  $ sudo ~/linux/tools/perf/perf lock con -abvo -Y mutex -E16 perf bench sched pipe
   ...
   contended   total wait     max wait     avg wait         type   caller

         171      1.55 ms     20.26 us      9.06 us        mutex   pipe_read+0x57
                          0xffffffffac6318e7  pipe_read+0x57
                          0xffffffffac623862  vfs_read+0x332
                          0xffffffffac62434b  ksys_read+0xbb
                          0xfffffffface604b2  do_syscall_64+0x82
                          0xffffffffad00012f  entry_SYSCALL_64_after_hwframe+0x76
          36    193.71 us     15.27 us      5.38 us        mutex   pipe_write+0x50
                          0xffffffffac631ee0  pipe_write+0x50
                          0xffffffffac6241db  vfs_write+0x3bb
                          0xffffffffac6244ab  ksys_write+0xbb
                          0xfffffffface604b2  do_syscall_64+0x82
                          0xffffffffad00012f  entry_SYSCALL_64_after_hwframe+0x76
           4     51.22 us     16.47 us     12.80 us        mutex   do_epoll_wait+0x24d
                          0xffffffffac691f0d  do_epoll_wait+0x24d
                          0xffffffffac69249b  do_epoll_pwait.part.0+0xb
                          0xffffffffac693ba5  __x64_sys_epoll_pwait+0x95
                          0xfffffffface604b2  do_syscall_64+0x82
                          0xffffffffad00012f  entry_SYSCALL_64_after_hwframe+0x76
           2     20.88 us     11.95 us     10.44 us        mutex   do_epoll_wait+0x24d
                          0xffffffffac691f0d  do_epoll_wait+0x24d
                          0xffffffffac693943  __x64_sys_epoll_wait+0x73
                          0xfffffffface604b2  do_syscall_64+0x82
                          0xffffffffad00012f  entry_SYSCALL_64_after_hwframe+0x76
           1      7.33 us      7.33 us      7.33 us        mutex   do_epoll_ctl+0x6c1
                          0xffffffffac692e01  do_epoll_ctl+0x6c1
                          0xffffffffac6937e0  __x64_sys_epoll_ctl+0x70
                          0xfffffffface604b2  do_syscall_64+0x82
                          0xffffffffad00012f  entry_SYSCALL_64_after_hwframe+0x76
           1      6.64 us      6.64 us      6.64 us        mutex   do_epoll_ctl+0x3d4
                          0xffffffffac692b14  do_epoll_ctl+0x3d4
                          0xffffffffac6937e0  __x64_sys_epoll_ctl+0x70
                          0xfffffffface604b2  do_syscall_64+0x82
                          0xffffffffad00012f  entry_SYSCALL_64_after_hwframe+0x76

  === owner stack trace ===

           3     31.24 us     15.27 us     10.41 us        mutex   pipe_read+0x348
                          0xffffffffac631bd8  pipe_read+0x348
                          0xffffffffac623862  vfs_read+0x332
                          0xffffffffac62434b  ksys_read+0xbb
                          0xfffffffface604b2  do_syscall_64+0x82
                          0xffffffffad00012f  entry_SYSCALL_64_after_hwframe+0x76
  ...

v6:
  Free allocated memory in error patch.
  Add description in man page.

v5: lore.kernel.org/[e-mail]
  Move duplicated code into function.
  Remove code to retrieve undesired callstack at the end of `contention_end()`.
  Other minor fix based on Namhyung's review.

v4: lore.kernel.org/[e-mail]
  Use `__sync_fetch_and_add()` to generate owner stackid automatically.
  Use `__sync_fetch_and_add(..., -1)` to workaround compiler error from
    `__sync_fetch_and_sub()`
  Remove unnecessary include headers.
  Dedicate on C-style comment.
  Other minor fix based on Namhyung's review.

v3: lore.kernel.org/[e-mail]
  Rename/shorten multiple variables.
  Implement owner stackid.
  Add description for lock function return code in `contention_end()`.
  Other minor fix based on Namhyung's review.

v2: lore.kernel.org/[e-mail]
  Fix logic deficit in v1 patch 2/4.

v1: lore.kernel.org/[e-mail]

Chun-Tse Shao (4):
  perf lock: Add bpf maps for owner stack tracing
  perf lock: Retrieve owner callstack in bpf program
  perf lock: Make rb_tree helper functions generic
  perf lock: Report owner stack in usermode

 tools/perf/Documentation/perf-lock.txt        |   6 +-
 tools/perf/builtin-lock.c                     |  56 +++-
 tools/perf/util/bpf_lock_contention.c         |  72 ++++-
 .../perf/util/bpf_skel/lock_contention.bpf.c  | 251 +++++++++++++++++-
 tools/perf/util/bpf_skel/lock_data.h          |   7 +
 tools/perf/util/lock-contention.h             |   7 +
 6 files changed, 372 insertions(+), 27 deletions(-)

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2.48.1.601.g30ceb7b040-goog