diff options
| author | Namhyung Kim <namhyung@kernel.org> | 2023-03-28 01:57:11 +0300 |
|---|---|---|
| committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2023-04-04 15:39:56 +0300 |
| commit | 84c3a2bb4c513ca9fd1326cf24d3729b769d9cf1 (patch) | |
| tree | f3e40c0eae98014a57f29d238b642b1abbf94f40 /tools/perf/util/bpf_skel | |
| parent | 35bf007e2ee0447166081646c0797bfa831b062f (diff) | |
| download | linux-84c3a2bb4c513ca9fd1326cf24d3729b769d9cf1.tar.xz | |
perf lock contention: Show detail failure reason for BPF
It can fail to collect lock stat from BPF for various reasons. For
example, I've got a report that sometimes time calculation seems wrong
in case of contended spinlocks. I suspect the time delta went negative
for some reason.
Count them separately and show in the output like below:
$ sudo perf lock contention -abE5 sleep 10
contended total wait max wait avg wait type caller
13 785.61 us 79.36 us 60.43 us spinlock remove_wait_queue+0x14
10 469.02 us 87.51 us 46.90 us spinlock prepare_to_wait+0x27
9 289.09 us 69.08 us 32.12 us spinlock finish_wait+0x36
114 251.05 us 8.56 us 2.20 us spinlock try_to_wake_up+0x1f5
132 188.63 us 5.01 us 1.43 us spinlock __wake_up_common_lock+0x62
=== output for debug ===
bad: 1, total: 279
bad rate: 0.36 %
histogram of failure reasons
task: 1
stack: 0
time: 0
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Hao Luo <haoluo@google.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: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20230327225711.245738-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Diffstat (limited to 'tools/perf/util/bpf_skel')
| -rw-r--r-- | tools/perf/util/bpf_skel/lock_contention.bpf.c | 13 |
1 files changed, 10 insertions, 3 deletions
diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c index ed9160999c32..3f4ee3992e81 100644 --- a/tools/perf/util/bpf_skel/lock_contention.bpf.c +++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c @@ -124,7 +124,9 @@ int lock_owner; int aggr_mode; /* error stat */ -int lost; +int task_fail; +int stack_fail; +int time_fail; static inline int can_record(u64 *ctx) { @@ -283,7 +285,7 @@ int contention_begin(u64 *ctx) bpf_map_update_elem(&tstamp, &pid, &zero, BPF_ANY); pelem = bpf_map_lookup_elem(&tstamp, &pid); if (pelem == NULL) { - lost++; + __sync_fetch_and_add(&task_fail, 1); return 0; } } @@ -296,7 +298,7 @@ int contention_begin(u64 *ctx) pelem->stack_id = bpf_get_stackid(ctx, &stacks, BPF_F_FAST_STACK_CMP | stack_skip); if (pelem->stack_id < 0) - lost++; + __sync_fetch_and_add(&stack_fail, 1); } else if (aggr_mode == LOCK_AGGR_TASK) { struct task_struct *task; @@ -340,6 +342,11 @@ int contention_end(u64 *ctx) return 0; duration = bpf_ktime_get_ns() - pelem->timestamp; + if ((__s64)duration < 0) { + bpf_map_delete_elem(&tstamp, &pid); + __sync_fetch_and_add(&time_fail, 1); + return 0; + } switch (aggr_mode) { case LOCK_AGGR_CALLER: |