kernel.git/tools/perf/util/lock-contention.h, branch master

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 contention: Symbolize zone->lock using BTF

2025-04-29T15:23:53Z

The struct zone is embedded in struct pglist_data which can be allocated for each NUMA node early in the boot process. As it's not a slab object nor a global lock, this was not symbolized. Since the zone->lock is often contended, it'd be nice if we can symbolize it. On NUMA systems, node_data array will have pointers for struct pglist_data. By following the pointer, it can calculate the address of each zone and its lock using BTF. On UMA, it can just use contig_page_data and its zones. The following example shows the zone lock contention at the end. $ sudo ./perf lock con -abl -E 5 -- ./perf bench sched messaging # Running 'sched/messaging' benchmark: # 20 sender and receiver processes per group # 10 groups == 400 processes run Total time: 0.038 [sec] contended total wait max wait avg wait address symbol 5167 18.17 ms 10.27 us 3.52 us ffff953340052d00 &kmem_cache_node (spinlock) 38 11.75 ms 465.49 us 309.13 us ffff95334060c480 &sock_inode_cache (spinlock) 3916 10.13 ms 10.43 us 2.59 us ffff953342aecb40 &kmem_cache_node (spinlock) 2963 10.02 ms 13.75 us 3.38 us ffff9533d2344098 &kmalloc-rnd-08-2k (spinlock) 216 5.05 ms 99.49 us 23.39 us ffff9542bf7d65d0 zone_lock (spinlock) 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 Cc: Stephane Eranian Cc: bpf@vger.kernel.org Cc: linux-mm@kvack.org Link: https://lore.kernel.org/r/20250401063055.7431-1-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 contention: Handle slab objects in -L/--lock-filter option

2024-12-23T16:53:08Z

This is to filter lock contention from specific slab objects only. Like in the lock symbol output, we can use '&' prefix to filter slab object names. root@virtme-ng:/home/namhyung/project/linux# tools/perf/perf lock con -abl sleep 1 contended total wait max wait avg wait address symbol 3 14.99 us 14.44 us 5.00 us ffffffff851c0940 pack_mutex (mutex) 2 2.75 us 2.56 us 1.38 us ffff98d7031fb498 &task_struct (mutex) 4 1.42 us 557 ns 355 ns ffff98d706311400 &kmalloc-cg-512 (mutex) 2 953 ns 714 ns 476 ns ffffffff851c3620 delayed_uprobe_lock (mutex) 1 929 ns 929 ns 929 ns ffff98d7031fb538 &task_struct (mutex) 3 561 ns 210 ns 187 ns ffffffff84a8b3a0 text_mutex (mutex) 1 479 ns 479 ns 479 ns ffffffff851b4cf8 tracepoint_srcu_srcu_usage (mutex) 2 320 ns 195 ns 160 ns ffffffff851cf840 pcpu_alloc_mutex (mutex) 1 212 ns 212 ns 212 ns ffff98d7031784d8 &signal_cache (mutex) 1 177 ns 177 ns 177 ns ffffffff851b4c28 tracepoint_srcu_srcu_usage (mutex) With the filter, it can show contentions from the task_struct only. root@virtme-ng:/home/namhyung/project/linux# tools/perf/perf lock con -abl -L '&task_struct' sleep 1 contended total wait max wait avg wait address symbol 2 1.97 us 1.71 us 987 ns ffff98d7032fd658 &task_struct (mutex) 1 1.20 us 1.20 us 1.20 us ffff98d7032fd6f8 &task_struct (mutex) It can work with other aggregation mode: root@virtme-ng:/home/namhyung/project/linux# tools/perf/perf lock con -ab -L '&task_struct' sleep 1 contended total wait max wait avg wait type caller 1 25.10 us 25.10 us 25.10 us mutex perf_event_exit_task+0x39 1 21.60 us 21.60 us 21.60 us mutex futex_exit_release+0x21 1 5.56 us 5.56 us 5.56 us mutex futex_exec_release+0x21 Committer testing: root@number:~# perf lock con -abl sleep 1 contended total wait max wait avg wait address symbol 1 20.80 us 20.80 us 20.80 us ffff9d417fbd65d0 (spinlock) 8 12.85 us 2.41 us 1.61 us ffff9d415eeb6a40 rq_lock (spinlock) 1 2.55 us 2.55 us 2.55 us ffff9d415f636a40 rq_lock (spinlock) 7 1.92 us 840 ns 274 ns ffff9d39c2cbc8c4 (spinlock) 1 1.23 us 1.23 us 1.23 us ffff9d415fb36a40 rq_lock (spinlock) 2 928 ns 738 ns 464 ns ffff9d39c1fa6660 &kmalloc-rnd-14-192 (rwlock) 4 788 ns 252 ns 197 ns ffffffffb8608a80 jiffies_lock (spinlock) 1 304 ns 304 ns 304 ns ffff9d39c2c979c4 (spinlock) 1 216 ns 216 ns 216 ns ffff9d3a0225c660 &kmalloc-rnd-14-192 (rwlock) 1 89 ns 89 ns 89 ns ffff9d3a0adbf3e0 &kmalloc-rnd-14-192 (rwlock) 1 61 ns 61 ns 61 ns ffff9d415f9b6a40 rq_lock (spinlock) root@number:~# uname -r 6.13.0-rc2 root@number:~# Signed-off-by: Namhyung Kim Tested-by: Arnaldo Carvalho de Melo Acked-by: Ian Rogers Cc: Adrian Hunter Cc: Andrii Nakryiko Cc: Chun-Tse Shao Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: Ingo Molnar Cc: Jiri Olsa Cc: Kan Liang Cc: Kees Cook Cc: Peter Zijlstra Cc: Roman Gushchin Cc: Song Liu Cc: Stephane Eranian Cc: Vlastimil Babka Link: https://lore.kernel.org/r/20241220060009.507297-5-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf lock: Move common lock contention code to new file

2024-12-18T19:24:33Z

Avoid references from util code to builtin-lock that require python stubs. Move the functions and related variables to util/lock-contention.c. Add max_stack_depth parameter to match_callstack_filter to avoid sharing a global variable. Signed-off-by: Ian Rogers Tested-by: Arnaldo Carvalho de Melo Acked-by: Arnaldo Carvalho de Melo Acked-by: Namhyung Kim Cc: Adrian Hunter Cc: Alexander Shishkin Cc: Andi Kleen Cc: Athira Rajeev Cc: Colin Ian King Cc: Dapeng Mi Cc: Howard Chu Cc: Ilya Leoshkevich Cc: Ingo Molnar Cc: James Clark Cc: Jiri Olsa Cc: Josh Poimboeuf Cc: Kan Liang Cc: Mark Rutland Cc: Michael Petlan Cc: Peter Zijlstra Cc: Thomas Richter Cc: Veronika Molnarova Cc: Weilin Wang Link: https://lore.kernel.org/r/20241119011644.971342-16-irogers@google.com Signed-off-by: Arnaldo Carvalho de Melo

perf lock contention: Add -G/--cgroup-filter option

2023-09-12T20:32:00Z

The -G/--cgroup-filter is to limit lock contention collection on the tasks in the specific cgroups only. $ sudo ./perf lock con -abt -G /user.slice/.../vte-spawn-52221fb8-b33f-4a52-b5c3-e35d1e6fc0e0.scope \ ./perf bench sched messaging # Running 'sched/messaging' benchmark: # 20 sender and receiver processes per group # 10 groups == 400 processes run Total time: 0.174 [sec] contended total wait max wait avg wait pid comm 4 114.45 us 60.06 us 28.61 us 214847 sched-messaging 2 111.40 us 60.84 us 55.70 us 214848 sched-messaging 2 106.09 us 59.42 us 53.04 us 214837 sched-messaging 1 81.70 us 81.70 us 81.70 us 214709 sched-messaging 68 78.44 us 6.83 us 1.15 us 214633 sched-messaging 69 73.71 us 2.69 us 1.07 us 214632 sched-messaging 4 72.62 us 60.83 us 18.15 us 214850 sched-messaging 2 71.75 us 67.60 us 35.88 us 214840 sched-messaging 2 69.29 us 67.53 us 34.65 us 214804 sched-messaging 2 69.00 us 68.23 us 34.50 us 214826 sched-messaging ... Export cgroup__new() function as it's needed from outside. Reviewed-by: Ian Rogers Signed-off-by: Namhyung Kim Tested-by: Arnaldo Carvalho de Melo Cc: Adrian Hunter Cc: Hao Luo Cc: Ingo Molnar Cc: Jiri Olsa Cc: Peter Zijlstra Cc: Song Liu Cc: bpf@vger.kernel.org Link: https://lore.kernel.org/r/20230906174903.346486-5-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf lock contention: Add --lock-cgroup option

2023-09-12T20:32:00Z

The --lock-cgroup option shows lock contention stats break down by cgroups. Add LOCK_AGGR_CGROUP mode and use it instead of use_cgroup field. $ sudo ./perf lock con -ab --lock-cgroup sleep 1 contended total wait max wait avg wait cgroup 8 15.70 us 6.34 us 1.96 us / 2 1.48 us 747 ns 738 ns /user.slice/.../app.slice/app-gnome-google\x2dchrome-6442.scope 1 848 ns 848 ns 848 ns /user.slice/.../session.slice/org.gnome.Shell@x11.service 1 220 ns 220 ns 220 ns /user.slice/.../session.slice/pipewire-pulse.service For now, the cgroup mode only works with BPF (-b). Committer notes: Remove -g as it is used in the other tools with a clear meaning of collect/show callchains. As agreed with Namhyung off list. Reviewed-by: Ian Rogers Signed-off-by: Namhyung Kim Tested-by: Arnaldo Carvalho de Melo Cc: Adrian Hunter Cc: Hao Luo Cc: Ingo Molnar Cc: Jiri Olsa Cc: Peter Zijlstra Cc: Song Liu Cc: bpf@vger.kernel.org Link: https://lore.kernel.org/r/20230906174903.346486-4-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf lock contention: Prepare to handle cgroups

2023-09-12T20:32:00Z

Save cgroup info and display cgroup names if requested. This is a preparation for the next patch. Reviewed-by: Ian Rogers Signed-off-by: Namhyung Kim Cc: Adrian Hunter Cc: Hao Luo Cc: Ingo Molnar Cc: Jiri Olsa Cc: Peter Zijlstra Cc: Song Liu Cc: bpf@vger.kernel.org Link: https://lore.kernel.org/r/20230906174903.346486-3-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf lock contention: Update total/bad stats for hidden entries

2023-04-07T00:52:37Z

When -E option is used, it only prints the given number of entries but the event stat at the end should have the numbers for entire entries. Likewise, -S option will hide entries that don't have the named function in the callstack. Also update event stat for them. Signed-off-by: Namhyung Kim Acked-by: Ian Rogers Cc: Adrian Hunter Cc: Hao Luo Cc: Ingo Molnar Cc: Jiri Olsa Cc: Juri Lelli Cc: Peter Zijlstra Cc: Song Liu Cc: bpf@vger.kernel.org Link: https://lore.kernel.org/r/20230406210611.1622492-2-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf lock contention: Add data failure stat

2023-04-07T00:52:31Z

It's possible to fail to update the data when the lock_stat map is full. We should check that case and show the number at the end. $ sudo ./perf lock con -ablv -E3 -- ./perf bench sched messaging ... contended total wait max wait avg wait address symbol 6157 208.48 ms 69.29 us 33.86 us ffff934c001c1f00 (spinlock) 4030 72.04 ms 61.84 us 17.88 us ffff934c000415c0 (spinlock) 3201 50.30 ms 47.73 us 15.71 us ffff934c2eead850 (spinlock) === output for debug === bad: 0, total: 13388 bad rate: 0.00 % histogram of failure reasons task: 0 stack: 0 time: 0 data: 0 <----- added Signed-off-by: Namhyung Kim Acked-by: Ian Rogers Cc: Adrian Hunter Cc: Hao Luo Cc: Ingo Molnar Cc: Jiri Olsa Cc: Juri Lelli Cc: Peter Zijlstra Cc: Song Liu Cc: bpf@vger.kernel.org Link: https://lore.kernel.org/r/20230406210611.1622492-2-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo