From 1ddf95f6d81fcb27d09db3f9c1f7ad51b835a2ac Mon Sep 17 00:00:00 2001 From: Ian Rogers Date: Mon, 14 Apr 2025 10:41:30 -0700 Subject: [PATCH] perf intel-tpebs: Don't close record on read MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Factor sending record control fd code into its own function. Rather than killing the record process send it a ping when reading. Timeouts were witnessed if done too frequently, so only ping for the first tpebs events. Don't kill the record command send it a stop command. As close isn't reliably called also close on evsel__exit. Add extra checks on the record being terminated to avoid warnings. Adjust the locking as needed and incorporate extra -Wthread-safety checks. Check to do six 500ms poll timeouts when sending commands, rather than the larger 3000ms, to allow the record process terminating to be better witnessed. Reviewed-by: Kan Liang Signed-off-by: Ian Rogers Tested-by: Weilin Wang Acked-by: Namhyung Kim Cc: Adrian Hunter Cc: Alexander Shishkin Cc: Alexandre Torgue Cc: Andreas Färber Cc: Caleb Biggers Cc: Ingo Molnar Cc: Jiri Olsa Cc: Manivannan Sadhasivam Cc: Mark Rutland Cc: Maxime Coquelin Cc: Perry Taylor Cc: Peter Zijlstra Cc: Thomas Falcon Link: https://lore.kernel.org/r/20250414174134.3095492-13-irogers@google.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/evsel.c | 2 + tools/perf/util/intel-tpebs.c | 200 +++++++++++++++++++++------------- 2 files changed, 129 insertions(+), 73 deletions(-) diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c index 2079ffab29f8b..07a3a4e3b7a47 100644 --- a/tools/perf/util/evsel.c +++ b/tools/perf/util/evsel.c @@ -1656,6 +1656,8 @@ void evsel__exit(struct evsel *evsel) { assert(list_empty(&evsel->core.node)); assert(evsel->evlist == NULL); + if (evsel__is_retire_lat(evsel)) + evsel__tpebs_close(evsel); bpf_counter__destroy(evsel); perf_bpf_filter__destroy(evsel); evsel__free_counts(evsel); diff --git a/tools/perf/util/intel-tpebs.c b/tools/perf/util/intel-tpebs.c index 44e86d0f93432..dc4985728b29a 100644 --- a/tools/perf/util/intel-tpebs.c +++ b/tools/perf/util/intel-tpebs.c @@ -33,6 +33,7 @@ bool tpebs_recording; static LIST_HEAD(tpebs_results); static pthread_t tpebs_reader_thread; static struct child_process tpebs_cmd; +static int control_fd[2], ack_fd[2]; static struct mutex tpebs_mtx; struct tpebs_retire_lat { @@ -51,8 +52,6 @@ struct tpebs_retire_lat { bool started; }; -static struct tpebs_retire_lat *tpebs_retire_lat__find(struct evsel *evsel); - static void tpebs_mtx_init(void) { mutex_init(&tpebs_mtx); @@ -66,7 +65,10 @@ static struct mutex *tpebs_mtx_get(void) return &tpebs_mtx; } -static int evsel__tpebs_start_perf_record(struct evsel *evsel, int control_fd[], int ack_fd[]) +static struct tpebs_retire_lat *tpebs_retire_lat__find(struct evsel *evsel) + EXCLUSIVE_LOCKS_REQUIRED(tpebs_mtx_get()); + +static int evsel__tpebs_start_perf_record(struct evsel *evsel) { const char **record_argv; int tpebs_event_size = 0, i = 0, ret; @@ -74,15 +76,13 @@ static int evsel__tpebs_start_perf_record(struct evsel *evsel, int control_fd[], char cpumap_buf[50]; struct tpebs_retire_lat *t; - mutex_lock(tpebs_mtx_get()); list_for_each_entry(t, &tpebs_results, nd) tpebs_event_size++; record_argv = malloc((10 + 2 * tpebs_event_size) * sizeof(*record_argv)); - if (!record_argv) { - mutex_unlock(tpebs_mtx_get()); + if (!record_argv) return -ENOMEM; - } + record_argv[i++] = "perf"; record_argv[i++] = "record"; record_argv[i++] = "-W"; @@ -118,7 +118,6 @@ static int evsel__tpebs_start_perf_record(struct evsel *evsel, int control_fd[], list_for_each_entry(t, &tpebs_results, nd) t->started = true; - mutex_unlock(tpebs_mtx_get()); return ret; } @@ -131,6 +130,11 @@ static int process_sample_event(const struct perf_tool *tool __maybe_unused, struct tpebs_retire_lat *t; mutex_lock(tpebs_mtx_get()); + if (tpebs_cmd.pid == 0) { + /* Record has terminated. */ + mutex_unlock(tpebs_mtx_get()); + return 0; + } t = tpebs_retire_lat__find(evsel); if (!t) { mutex_unlock(tpebs_mtx_get()); @@ -180,17 +184,98 @@ static void *__sample_reader(void *arg __maybe_unused) return NULL; } +static int tpebs_send_record_cmd(const char *msg) EXCLUSIVE_LOCKS_REQUIRED(tpebs_mtx_get()) +{ + struct pollfd pollfd = { .events = POLLIN, }; + int ret, len, retries = 0; + char ack_buf[8]; + + /* Check if the command exited before the send, done with the lock held. */ + if (tpebs_cmd.pid == 0) + return 0; + + /* + * Let go of the lock while sending/receiving as blocking can starve the + * sample reading thread. + */ + mutex_unlock(tpebs_mtx_get()); + + /* Send perf record command.*/ + len = strlen(msg); + ret = write(control_fd[1], msg, len); + if (ret != len) { + pr_err("perf record control write control message '%s' failed\n", msg); + ret = -EPIPE; + goto out; + } + + if (!strcmp(msg, EVLIST_CTL_CMD_STOP_TAG)) { + ret = 0; + goto out; + } + + /* Wait for an ack. */ + pollfd.fd = ack_fd[0]; + + /* + * We need this poll to ensure the ack_fd PIPE will not hang + * when perf record failed for any reason. The timeout value + * 3000ms is an empirical selection. + */ +again: + if (!poll(&pollfd, 1, 500)) { + if (check_if_command_finished(&tpebs_cmd)) { + ret = 0; + goto out; + } + + if (retries++ < 6) + goto again; + pr_err("tpebs failed: perf record ack timeout for '%s'\n", msg); + ret = -ETIMEDOUT; + goto out; + } + + if (!(pollfd.revents & POLLIN)) { + if (check_if_command_finished(&tpebs_cmd)) { + ret = 0; + goto out; + } + + pr_err("tpebs failed: did not received an ack for '%s'\n", msg); + ret = -EPIPE; + goto out; + } + + ret = read(ack_fd[0], ack_buf, sizeof(ack_buf)); + if (ret > 0) + ret = strcmp(ack_buf, EVLIST_CTL_CMD_ACK_TAG); + else + pr_err("tpebs: perf record control ack failed\n"); +out: + /* Re-take lock as expected by caller. */ + mutex_lock(tpebs_mtx_get()); + return ret; +} + /* * tpebs_stop - stop the sample data read thread and the perf record process. */ -static int tpebs_stop(void) +static int tpebs_stop(void) EXCLUSIVE_LOCKS_REQUIRED(tpebs_mtx_get()) { int ret = 0; /* Like tpebs_start, we should only run tpebs_end once. */ if (tpebs_cmd.pid != 0) { - kill(tpebs_cmd.pid, SIGTERM); + tpebs_send_record_cmd(EVLIST_CTL_CMD_STOP_TAG); + tpebs_cmd.pid = 0; + mutex_unlock(tpebs_mtx_get()); pthread_join(tpebs_reader_thread, NULL); + mutex_lock(tpebs_mtx_get()); + close(control_fd[0]); + close(control_fd[1]); + close(ack_fd[0]); + close(ack_fd[1]); close(tpebs_cmd.out); ret = finish_command(&tpebs_cmd); tpebs_cmd.pid = 0; @@ -352,13 +437,15 @@ int evsel__tpebs_open(struct evsel *evsel) return 0; /* Only start the events once. */ if (tpebs_cmd.pid != 0) { - struct tpebs_retire_lat *t = tpebs_retire_lat__find(evsel); + struct tpebs_retire_lat *t; + bool valid; - if (!t || !t->started) { - /* Fail, as the event wasn't started. */ - return -EBUSY; - } - return 0; + mutex_lock(tpebs_mtx_get()); + t = tpebs_retire_lat__find(evsel); + valid = t && t->started; + mutex_unlock(tpebs_mtx_get()); + /* May fail as the event wasn't started. */ + return valid ? 0 : -EBUSY; } ret = evsel__tpebs_prepare(evsel); @@ -367,12 +454,7 @@ int evsel__tpebs_open(struct evsel *evsel) mutex_lock(tpebs_mtx_get()); tpebs_empty = list_empty(&tpebs_results); - mutex_unlock(tpebs_mtx_get()); if (!tpebs_empty) { - struct pollfd pollfd = { .events = POLLIN, }; - int control_fd[2], ack_fd[2], len; - char ack_buf[8]; - /*Create control and ack fd for --control*/ if (pipe(control_fd) < 0) { pr_err("tpebs: Failed to create control fifo"); @@ -385,7 +467,7 @@ int evsel__tpebs_open(struct evsel *evsel) goto out; } - ret = evsel__tpebs_start_perf_record(evsel, control_fd, ack_fd); + ret = evsel__tpebs_start_perf_record(evsel); if (ret) goto out; @@ -397,53 +479,16 @@ int evsel__tpebs_open(struct evsel *evsel) ret = -1; goto out; } - /* Wait for perf record initialization.*/ - len = strlen(EVLIST_CTL_CMD_ENABLE_TAG); - ret = write(control_fd[1], EVLIST_CTL_CMD_ENABLE_TAG, len); - if (ret != len) { - pr_err("perf record control write control message failed\n"); - goto out; - } - - /* wait for an ack */ - pollfd.fd = ack_fd[0]; - - /* - * We need this poll to ensure the ack_fd PIPE will not hang - * when perf record failed for any reason. The timeout value - * 3000ms is an empirical selection. - */ - if (!poll(&pollfd, 1, 3000)) { - pr_err("tpebs failed: perf record ack timeout\n"); - ret = -1; - goto out; - } - - if (!(pollfd.revents & POLLIN)) { - pr_err("tpebs failed: did not received an ack\n"); - ret = -1; - goto out; - } - - ret = read(ack_fd[0], ack_buf, sizeof(ack_buf)); - if (ret > 0) - ret = strcmp(ack_buf, EVLIST_CTL_CMD_ACK_TAG); - else { - pr_err("tpebs: perf record control ack failed\n"); - goto out; - } -out: - close(control_fd[0]); - close(control_fd[1]); - close(ack_fd[0]); - close(ack_fd[1]); + ret = tpebs_send_record_cmd(EVLIST_CTL_CMD_ENABLE_TAG); } +out: if (ret) { struct tpebs_retire_lat *t = tpebs_retire_lat__find(evsel); list_del_init(&t->nd); tpebs_retire_lat__delete(t); } + mutex_unlock(tpebs_mtx_get()); return ret; } @@ -452,6 +497,7 @@ int evsel__tpebs_read(struct evsel *evsel, int cpu_map_idx, int thread) struct perf_counts_values *count, *old_count = NULL; struct tpebs_retire_lat *t; uint64_t val; + int ret; /* Only set retire_latency value to the first CPU and thread. */ if (cpu_map_idx != 0 || thread != 0) @@ -462,14 +508,20 @@ int evsel__tpebs_read(struct evsel *evsel, int cpu_map_idx, int thread) count = perf_counts(evsel->counts, cpu_map_idx, thread); - /* - * Need to stop the forked record to ensure get sampled data from the - * PIPE to process and get non-zero retire_lat value for hybrid. - */ - tpebs_stop(); - mutex_lock(tpebs_mtx_get()); t = tpebs_retire_lat__find(evsel); + /* + * If reading the first tpebs result, send a ping to the record + * process. Allow the sample reader a chance to read by releasing and + * reacquiring the lock. + */ + if (&t->nd == tpebs_results.next) { + ret = tpebs_send_record_cmd(EVLIST_CTL_CMD_PING_TAG); + mutex_unlock(tpebs_mtx_get()); + if (ret) + return ret; + mutex_lock(tpebs_mtx_get()); + } val = rint(t->val); mutex_unlock(tpebs_mtx_get()); @@ -498,10 +550,12 @@ void evsel__tpebs_close(struct evsel *evsel) mutex_lock(tpebs_mtx_get()); t = tpebs_retire_lat__find(evsel); - list_del_init(&t->nd); - tpebs_retire_lat__delete(t); - mutex_unlock(tpebs_mtx_get()); + if (t) { + list_del_init(&t->nd); + tpebs_retire_lat__delete(t); - if (list_empty(&tpebs_results)) - tpebs_stop(); + if (list_empty(&tpebs_results)) + tpebs_stop(); + } + mutex_unlock(tpebs_mtx_get()); } -- 2.39.5