diff options
author | Namhyung Kim | 2024-02-27 21:33:35 -0800 |
---|---|---|
committer | Namhyung Kim | 2024-02-29 13:53:56 -0800 |
commit | b44d66536859393772c67cb1da65345127f692e0 (patch) | |
tree | 4b0a7da48fdc47ae727eeef00f83bf2a7509dd18 /tools/perf | |
parent | 97b6b4ac1c5dd42a473a4f8e775d97476c5da038 (diff) |
perf lock contention: Account contending locks too
Currently it accounts the contention using delta between timestamps in
lock:contention_begin and lock:contention_end tracepoints. But it means
the lock should see the both events during the monitoring period.
Actually there are 4 cases that happen with the monitoring:
monitoring period
/ \
| |
1: B------+-----------------------+--------E
2: B----+-------------E |
3: | B-----------+----E
4: | B-------------E |
| |
t0 t1
where B and E mean contention BEGIN and END, respectively. So it only
accounts the case 4 for now. It seems there's no way to handle the case
1. The case 2 might be handled if it saved the timestamp (t0), but it
lacks the information from the B notably the flags which shows the lock
types. Also it could be a nested lock which it currently ignores. So
I think we should ignore the case 2.
However we can handle the case 3 if we save the timestamp (t1) at the
end of the period. And then it can iterate the map entries in the
userspace and update the lock stat accordinly.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Reviewed-by: Ian Rogers <irogers@google.com>
Reviwed-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Song Liu <song@kernel.org>
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20240228053335.312776-1-namhyung@kernel.org
Diffstat (limited to 'tools/perf')
-rw-r--r-- | tools/perf/util/bpf_lock_contention.c | 120 | ||||
-rw-r--r-- | tools/perf/util/bpf_skel/lock_contention.bpf.c | 16 | ||||
-rw-r--r-- | tools/perf/util/bpf_skel/lock_data.h | 7 |
3 files changed, 136 insertions, 7 deletions
diff --git a/tools/perf/util/bpf_lock_contention.c b/tools/perf/util/bpf_lock_contention.c index 31ff19afc20c..3549180c7885 100644 --- a/tools/perf/util/bpf_lock_contention.c +++ b/tools/perf/util/bpf_lock_contention.c @@ -179,6 +179,123 @@ int lock_contention_prepare(struct lock_contention *con) return 0; } +/* + * Run the BPF program directly using BPF_PROG_TEST_RUN to update the end + * timestamp in ktime so that it can calculate delta easily. + */ +static void mark_end_timestamp(void) +{ + DECLARE_LIBBPF_OPTS(bpf_test_run_opts, opts, + .flags = BPF_F_TEST_RUN_ON_CPU, + ); + int prog_fd = bpf_program__fd(skel->progs.end_timestamp); + + bpf_prog_test_run_opts(prog_fd, &opts); +} + +static void update_lock_stat(int map_fd, int pid, u64 end_ts, + enum lock_aggr_mode aggr_mode, + struct tstamp_data *ts_data) +{ + u64 delta; + struct contention_key stat_key = {}; + struct contention_data stat_data; + + if (ts_data->timestamp >= end_ts) + return; + + delta = end_ts - ts_data->timestamp; + + switch (aggr_mode) { + case LOCK_AGGR_CALLER: + stat_key.stack_id = ts_data->stack_id; + break; + case LOCK_AGGR_TASK: + stat_key.pid = pid; + break; + case LOCK_AGGR_ADDR: + stat_key.lock_addr_or_cgroup = ts_data->lock; + break; + case LOCK_AGGR_CGROUP: + /* TODO */ + return; + default: + return; + } + + if (bpf_map_lookup_elem(map_fd, &stat_key, &stat_data) < 0) + return; + + stat_data.total_time += delta; + stat_data.count++; + + if (delta > stat_data.max_time) + stat_data.max_time = delta; + if (delta < stat_data.min_time) + stat_data.min_time = delta; + + bpf_map_update_elem(map_fd, &stat_key, &stat_data, BPF_EXIST); +} + +/* + * Account entries in the tstamp map (which didn't see the corresponding + * lock:contention_end tracepoint) using end_ts. + */ +static void account_end_timestamp(struct lock_contention *con) +{ + int ts_fd, stat_fd; + int *prev_key, key; + u64 end_ts = skel->bss->end_ts; + int total_cpus; + enum lock_aggr_mode aggr_mode = con->aggr_mode; + struct tstamp_data ts_data, *cpu_data; + + /* Iterate per-task tstamp map (key = TID) */ + ts_fd = bpf_map__fd(skel->maps.tstamp); + stat_fd = bpf_map__fd(skel->maps.lock_stat); + + prev_key = NULL; + while (!bpf_map_get_next_key(ts_fd, prev_key, &key)) { + if (bpf_map_lookup_elem(ts_fd, &key, &ts_data) == 0) { + int pid = key; + + if (aggr_mode == LOCK_AGGR_TASK && con->owner) + pid = ts_data.flags; + + update_lock_stat(stat_fd, pid, end_ts, aggr_mode, + &ts_data); + } + + prev_key = &key; + } + + /* Now it'll check per-cpu tstamp map which doesn't have TID. */ + if (aggr_mode == LOCK_AGGR_TASK || aggr_mode == LOCK_AGGR_CGROUP) + return; + + total_cpus = cpu__max_cpu().cpu; + ts_fd = bpf_map__fd(skel->maps.tstamp_cpu); + + cpu_data = calloc(total_cpus, sizeof(*cpu_data)); + if (cpu_data == NULL) + return; + + prev_key = NULL; + while (!bpf_map_get_next_key(ts_fd, prev_key, &key)) { + if (bpf_map_lookup_elem(ts_fd, &key, cpu_data) < 0) + goto next; + + for (int i = 0; i < total_cpus; i++) { + update_lock_stat(stat_fd, -1, end_ts, aggr_mode, + &cpu_data[i]); + } + +next: + prev_key = &key; + } + free(cpu_data); +} + int lock_contention_start(void) { skel->bss->enabled = 1; @@ -188,6 +305,7 @@ int lock_contention_start(void) int lock_contention_stop(void) { skel->bss->enabled = 0; + mark_end_timestamp(); return 0; } @@ -301,6 +419,8 @@ int lock_contention_read(struct lock_contention *con) if (stack_trace == NULL) return -1; + account_end_timestamp(con); + if (con->aggr_mode == LOCK_AGGR_TASK) { struct thread *idle = __machine__findnew_thread(machine, /*pid=*/0, diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c index 95cd8414f6ef..fb54bd38e7d0 100644 --- a/tools/perf/util/bpf_skel/lock_contention.bpf.c +++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c @@ -19,13 +19,6 @@ #define LCB_F_PERCPU (1U << 4) #define LCB_F_MUTEX (1U << 5) -struct tstamp_data { - __u64 timestamp; - __u64 lock; - __u32 flags; - __s32 stack_id; -}; - /* callstack storage */ struct { __uint(type, BPF_MAP_TYPE_STACK_TRACE); @@ -140,6 +133,8 @@ int perf_subsys_id = -1; /* determine the key of lock stat */ int aggr_mode; +__u64 end_ts; + /* error stat */ int task_fail; int stack_fail; @@ -559,4 +554,11 @@ int BPF_PROG(collect_lock_syms) return 0; } +SEC("raw_tp/bpf_test_finish") +int BPF_PROG(end_timestamp) +{ + end_ts = bpf_ktime_get_ns(); + return 0; +} + char LICENSE[] SEC("license") = "Dual BSD/GPL"; diff --git a/tools/perf/util/bpf_skel/lock_data.h b/tools/perf/util/bpf_skel/lock_data.h index 08482daf61be..36af11faad03 100644 --- a/tools/perf/util/bpf_skel/lock_data.h +++ b/tools/perf/util/bpf_skel/lock_data.h @@ -3,6 +3,13 @@ #ifndef UTIL_BPF_SKEL_LOCK_DATA_H #define UTIL_BPF_SKEL_LOCK_DATA_H +struct tstamp_data { + u64 timestamp; + u64 lock; + u32 flags; + u32 stack_id; +}; + struct contention_key { u32 stack_id; u32 pid; |