diff options
| author | Namhyung Kim <namhyung@kernel.org> | 2022-09-12 08:53:13 +0300 |
|---|---|---|
| committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2022-10-04 14:55:22 +0300 |
| commit | 96532a83ee8e30035e584b046c859adb001a3b8d (patch) | |
| tree | 7c9a84cc94b56abd8c9fb799690a0f4d25d38b38 /tools/perf/util | |
| parent | a6eaf966bce9a30ccd0969fed195e051b8904983 (diff) | |
| download | linux-96532a83ee8e30035e584b046c859adb001a3b8d.tar.xz | |
perf lock contention: Allow to change stack depth and skip
It needs stack traces to find callers of locks. To minimize the
performance overhead it only collects up to 8 entries for each stack
trace. And it skips first 3 entries as they came from BPF, tracepoint
and lock functions which are not interested for most users.
But it turned out that those numbers are different in some
configuration. Using fixed number can result in non meaningful caller
names. Let's make them adjustable with --stack-depth and --skip-stack
options.
On my setup, the default output is like below:
# /perf lock con -ab -F contended,wait_total sleep 3
contended total wait type caller
28 4.55 ms rwlock:W __bpf_trace_contention_begin+0xb
33 1.67 ms rwlock:W __bpf_trace_contention_begin+0xb
12 580.28 us spinlock __bpf_trace_contention_begin+0xb
60 240.54 us rwsem:R __bpf_trace_contention_begin+0xb
27 64.45 us spinlock __bpf_trace_contention_begin+0xb
If I change the stack skip to 5, the result will be like:
# perf lock con -ab -F contended,wait_total --stack-skip 5 sleep 3
contended total wait type caller
32 715.45 us spinlock folio_lruvec_lock_irqsave+0x61
26 550.22 us spinlock folio_lruvec_lock_irqsave+0x61
15 486.93 us rwsem:R mmap_read_lock+0x13
12 139.66 us rwsem:W vm_mmap_pgoff+0x93
1 7.04 us spinlock tick_do_update_jiffies64+0x25
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20220912055314.744552-4-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools/perf/util')
| -rw-r--r-- | tools/perf/util/bpf_lock_contention.c | 7 | ||||
| -rw-r--r-- | tools/perf/util/lock-contention.h | 2 |
2 files changed, 6 insertions, 3 deletions
diff --git a/tools/perf/util/bpf_lock_contention.c b/tools/perf/util/bpf_lock_contention.c index 6545bee65347..ef5323c78ffc 100644 --- a/tools/perf/util/bpf_lock_contention.c +++ b/tools/perf/util/bpf_lock_contention.c @@ -41,6 +41,7 @@ int lock_contention_prepare(struct lock_contention *con) return -1; } + bpf_map__set_value_size(skel->maps.stacks, con->max_stack * sizeof(u64)); bpf_map__set_max_entries(skel->maps.stacks, con->map_nr_entries); bpf_map__set_max_entries(skel->maps.lock_stat, con->map_nr_entries); @@ -115,7 +116,7 @@ int lock_contention_read(struct lock_contention *con) struct lock_contention_data data; struct lock_stat *st; struct machine *machine = con->machine; - u64 stack_trace[CONTENTION_STACK_DEPTH]; + u64 stack_trace[con->max_stack]; fd = bpf_map__fd(skel->maps.lock_stat); stack = bpf_map__fd(skel->maps.stacks); @@ -146,9 +147,9 @@ int lock_contention_read(struct lock_contention *con) bpf_map_lookup_elem(stack, &key, stack_trace); /* skip BPF + lock internal functions */ - idx = CONTENTION_STACK_SKIP; + idx = con->stack_skip; while (is_lock_function(machine, stack_trace[idx]) && - idx < CONTENTION_STACK_DEPTH - 1) + idx < con->max_stack - 1) idx++; st->addr = stack_trace[idx]; diff --git a/tools/perf/util/lock-contention.h b/tools/perf/util/lock-contention.h index bdb6e2a61e5b..67db311fc9df 100644 --- a/tools/perf/util/lock-contention.h +++ b/tools/perf/util/lock-contention.h @@ -115,6 +115,8 @@ struct lock_contention { struct hlist_head *result; unsigned long map_nr_entries; unsigned long lost; + int max_stack; + int stack_skip; }; #ifdef HAVE_BPF_SKEL |