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
...
v5:
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/20250130052510.860318-1-ctshao@xxxxxxxxxx
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/20250129001905.619859-1-ctshao@xxxxxxxxxx
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/20250113052220.2105645-1-ctshao@xxxxxxxxxx
Fix logic deficit in v1 patch 2/4.
v1: lore.kernel.org/20250110051346.1507178-1-ctshao@xxxxxxxxxx
Chun-Tse Shao (5):
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
perf lock: Update documentation for -o option in contention mode
tools/perf/builtin-lock.c | 59 +++-
tools/perf/util/bpf_lock_contention.c | 68 ++++-
.../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 +
5 files changed, 367 insertions(+), 25 deletions(-)
--
2.48.1.502.g6dc24dfdaf-goog
