kernel.git/tools/perf/builtin-lock.c, branch master

perf lock: Fix segfault due to missing kernel map

2025-11-13T20:17:41Z

Kernel maps are encoded in PERF_RECORD_MMAP2 samples but "perf lock report" and "perf lock contention" do not process MMAP2 samples. Because of that, machine->vmlinux_map stays NULL and any later access triggers a segmentation fault. Fix it by adding ->mmap2() callbacks. Fixes: 53b00ff358dc75b1 ("perf record: Make --buildid-mmap the default") Reported-by: Tycho Andersen (AMD) Reviewed-by: Ian Rogers Signed-off-by: Ravi Bangoria Tested-by: Tycho Andersen (AMD) Cc: Adrian Hunter Cc: Alexander Shishkin Cc: Ananth Narayan Cc: Ingo Molnar Cc: James Clark Cc: Jiri Olsa Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Sandipan Das Cc: Santosh Shukla Signed-off-by: Arnaldo Carvalho de Melo

perf lock: Provide a host_env for session new

2025-09-13T00:53:03Z

When "perf lock con" is run in a live mode, with no data file, a host environment must be provided. Testing missed this as a failing assert was creating the 1 line of expected stderr output. $ sudo perf lock con -ab true perf: util/session.c:195: __perf_session__new: Assertion `host_env != NULL' failed. Aborted Fixes: 525a599badeeafba ("perf env: Remove global perf_env") Signed-off-by: Ian Rogers Signed-off-by: Namhyung Kim

perf session: Add accessor for session->header.env

2025-07-25T17:37:56Z

The perf_env from the header in the session is frequently accessed, add an accessor function rather than access directly. Cache the value to avoid repeated calls. No behavioral change. Signed-off-by: Ian Rogers Link: https://lore.kernel.org/r/20250724163302.596743-10-irogers@google.com Signed-off-by: Namhyung Kim

perf lock contention: Reject more than 10ms delays for safety

2025-05-31T11:45:24Z

Delaying kernel operations can be dangerous and the kernel may kill (non-sleepable) BPF programs running for long in the future. Limit the max delay to 10ms and update the document about it. $ sudo ./perf lock con -abl -J 100000us@cgroup_mutex true lock delay is too long: 100000us (> 10ms) Usage: perf lock contention [] -J, --inject-delay Inject delays to specific locks Suggested-by: Alexei Starovoitov Signed-off-by: Namhyung Kim Cc: Adrian Hunter Cc: Ian Rogers Cc: Ingo Molnar Cc: Jiri Olsa Cc: Kan Liang Cc: Peter Zijlstra Cc: Song Liu Link: https://lore.kernel.org/r/20250515181042.555189-1-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf lock contention: Add -J/--inject-delay option

2025-05-09T17:32:15Z

This is to slow down lock acquistion (on contention locks) deliberately. A possible use case is to estimate impact on application performance by optimization of kernel locking behavior. By delaying the lock it can simulate the worse condition as a control group, and then compare with the current behavior as a optimized condition. The syntax is 'time@function' and the time can have unit suffix like "us" and "ms". For example, I ran a simple test like below. $ sudo perf lock con -abl -L tasklist_lock -- \ sh -c 'for i in $(seq 1000); do sleep 1 & done; wait' contended total wait max wait avg wait address symbol 92 1.18 ms 199.54 us 12.79 us ffffffff8a806080 tasklist_lock (rwlock) The contention count was 92 and the average wait time was around 10 us. But if I add 100 usec of delay to the tasklist_lock, $ sudo perf lock con -abl -L tasklist_lock -J 100us@tasklist_lock -- \ sh -c 'for i in $(seq 1000); do sleep 1 & done; wait' contended total wait max wait avg wait address symbol 190 15.67 ms 230.10 us 82.46 us ffffffff8a806080 tasklist_lock (rwlock) The contention count increased and the average wait time was up closed to 100 usec. If I increase the delay even more, $ sudo perf lock con -abl -L tasklist_lock -J 1ms@tasklist_lock -- \ sh -c 'for i in $(seq 1000); do sleep 1 & done; wait' contended total wait max wait avg wait address symbol 1002 2.80 s 3.01 ms 2.80 ms ffffffff8a806080 tasklist_lock (rwlock) Now every sleep process had contention and the wait time was more than 1 msec. This is on my 4 CPU laptop so I guess one CPU has the lock while other 3 are waiting for it mostly. For simplicity, it only supports global locks for now. Committer testing: root@number:~# grep -m1 'model name' /proc/cpuinfo model name : AMD Ryzen 9 9950X3D 16-Core Processor root@number:~# perf lock con -abl -L tasklist_lock -- sh -c 'for i in $(seq 1000); do sleep 1 & done; wait' contended total wait max wait avg wait address symbol 142 453.85 us 25.39 us 3.20 us ffffffffae808080 tasklist_lock (rwlock) root@number:~# perf lock con -abl -L tasklist_lock -J 100us@tasklist_lock -- sh -c 'for i in $(seq 1000); do sleep 1 & done; wait' contended total wait max wait avg wait address symbol 1040 2.39 s 3.11 ms 2.30 ms ffffffffae808080 tasklist_lock (rwlock) root@number:~# perf lock con -abl -L tasklist_lock -J 1ms@tasklist_lock -- sh -c 'for i in $(seq 1000); do sleep 1 & done; wait' contended total wait max wait avg wait address symbol 1025 24.72 s 31.01 ms 24.12 ms ffffffffae808080 tasklist_lock (rwlock) root@number:~# Suggested-by: Stephane Eranian Signed-off-by: Namhyung Kim Tested-by: Arnaldo Carvalho de Melo Cc: Adrian Hunter Cc: Ian Rogers Cc: Ingo Molnar Cc: Jiri Olsa Cc: Kan Liang Cc: Peter Zijlstra Cc: Song Liu Link: https://lore.kernel.org/r/20250509171950.183591-1-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf lock: Report owner stack in usermode

2025-02-28T18:09:02Z

This patch parses `owner_lock_stat` into a RB tree, enabling ordered reporting of owner lock statistics with stack traces. It also updates the documentation for the `-o` option in contention mode, decouples `-o` from `-t`, and issues a warning to inform users about the new behavior of `-ov`. Example output: $ sudo ~/linux/tools/perf/perf lock con -abvo -Y mutex-spin -E3 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 === 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 ... Signed-off-by: Chun-Tse Shao Tested-by: Athira Rajeev Link: https://lore.kernel.org/r/20250227003359.732948-5-ctshao@google.com Signed-off-by: Namhyung Kim

perf lock: Make rb_tree helper functions generic

2025-02-28T08:29:37Z

The rb_tree helper functions can be reused for parsing `owner_lock_stat` into rb tree for sorting. Signed-off-by: Chun-Tse Shao Tested-by: Athira Rajeev Link: https://lore.kernel.org/r/20250227003359.732948-4-ctshao@google.com Signed-off-by: Namhyung Kim

perf lock: Rename fields in lock_type_table

2025-01-17T18:12:41Z

`lock_type_table` contains `name` and `str` which can be confusing. Rename them to `flags_name` and `lock_name` and add descriptions to enhance understanding. Tested by building perf for x86. Reviewed-by: Namhyung Kim Signed-off-by: Chun-Tse Shao Cc: nick.forrington@arm.com Link: https://lore.kernel.org/r/20250116235838.2769691-3-ctshao@google.com Signed-off-by: Namhyung Kim

perf lock: Add percpu-rwsem for type filter

2025-01-17T18:12:40Z

percpu-rwsem was missing in man page. And for backward compatibility, replace `pcpu-sem` with `percpu-rwsem` before parsing lock name. Tested `./perf lock con -ab -Y pcpu-sem` and `./perf lock con -ab -Y percpu-rwsem` Fixes: 4f701063bfa2 ("perf lock contention: Show lock type with address") Reviewed-by: Namhyung Kim Signed-off-by: Chun-Tse Shao Cc: nick.forrington@arm.com Link: https://lore.kernel.org/r/20250116235838.2769691-2-ctshao@google.com Signed-off-by: Namhyung Kim

perf lock: Fix parse_lock_type which only retrieve one lock flag

2025-01-17T18:11:57Z

`parse_lock_type` can only add the first lock flag in `lock_type_table` given input `str`. For example, for `Y rwlock`, it only adds `rwlock:R` into this perf session. Another example is for `-Y mutex`, it only adds the mutex without `LCB_F_SPIN` flag. The patch fixes this issue, makes sure both `rwlock:R` and `rwlock:W` will be added with `-Y rwlock`, and so on. Testing: $ ./perf lock con -ab -Y mutex,rwlock -- perf bench sched pipe # Running 'sched/pipe' benchmark: # Executed 1000000 pipe operations between two processes Total time: 9.313 [sec] 9.313976 usecs/op 107365 ops/sec contended total wait max wait avg wait type caller 176 1.65 ms 19.43 us 9.38 us mutex pipe_read+0x57 34 180.14 us 10.93 us 5.30 us mutex pipe_write+0x50 7 77.48 us 16.09 us 11.07 us mutex do_epoll_wait+0x24d 7 74.70 us 13.50 us 10.67 us mutex do_epoll_wait+0x24d 3 35.97 us 14.44 us 11.99 us rwlock:W ep_done_scan+0x2d 3 35.00 us 12.23 us 11.66 us rwlock:W do_epoll_wait+0x255 2 15.88 us 11.96 us 7.94 us rwlock:W do_epoll_wait+0x47c 1 15.23 us 15.23 us 15.23 us rwlock:W do_epoll_wait+0x4d0 1 14.26 us 14.26 us 14.26 us rwlock:W ep_done_scan+0x2d 2 14.00 us 7.99 us 7.00 us mutex pipe_read+0x282 1 12.29 us 12.29 us 12.29 us rwlock:R ep_poll_callback+0x35 1 12.02 us 12.02 us 12.02 us rwlock:W do_epoll_ctl+0xb65 1 10.25 us 10.25 us 10.25 us rwlock:R ep_poll_callback+0x35 1 7.86 us 7.86 us 7.86 us mutex do_epoll_ctl+0x6c1 1 5.04 us 5.04 us 5.04 us mutex do_epoll_ctl+0x3d4 [namhyung: Add a comment and rename to 'mutex:spin' for consistency Fixes: d783ea8f62c4 ("perf lock contention: Simplify parse_lock_type()") Reviewed-by: Namhyung Kim Signed-off-by: Chun-Tse Shao Cc: nick.forrington@arm.com Link: https://lore.kernel.org/r/20250116235838.2769691-1-ctshao@google.com Signed-off-by: Namhyung Kim