Re: [RFC PATCH v17 3/8] perf stat: Fork and launch perf record when perf stat needs to get retire latency value for a metric.

Namhyung Kim
2024-07-18T05:56:01Z

On Fri, Jul 12, 2024 at 03:09:25PM -0400, weilin.wang@intel.com wrote:
> From: Weilin Wang <weilin.wang@intel.com>
>
> When retire_latency value is used in a metric formula, evsel would fork a perf
> record process with "-e" and "-W" options. Perf record will collect required
> retire_latency values in parallel while perf stat is collecting counting values.
>
> At the point of time that perf stat stops counting, evsel would stop perf record
> by sending sigterm signal to perf record process. Sampled data will be process
> to get retire latency value. Another thread is required to synchronize between
> perf stat and perf record when we pass data through pipe.
>
> Retire_latency evsel is not opened for perf stat so that there is no counter
> wasted on it. This commit includes code suggested by Namhyung to adjust reading
> size for groups that include retire_latency evsels.
>
> Signed-off-by: Weilin Wang <weilin.wang@intel.com>
> ---
> tools/perf/builtin-stat.c | 4 +
> tools/perf/util/Build | 1 +
> tools/perf/util/evlist.c | 2 +
> tools/perf/util/evsel.c | 66 +++++-
> tools/perf/util/intel-tpebs.c | 430 ++++++++++++++++++++++++++++++++++
> tools/perf/util/intel-tpebs.h | 35 +++
> 6 files changed, 536 insertions(+), 2 deletions(-)
> create mode 100644 tools/perf/util/intel-tpebs.c
> create mode 100644 tools/perf/util/intel-tpebs.h
>
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index 661832756a24..68125bd75b37 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -70,6 +70,7 @@
> #include "util/bpf_counter.h"
> #include "util/iostat.h"
> #include "util/util.h"
> +#include "util/intel-tpebs.h"
> #include "asm/bug.h"
>
> #include <linux/time64.h>
> @@ -683,6 +684,9 @@ static enum counter_recovery stat_handle_error(struct evsel *counter)
>
> if (child_pid != -1)
> kill(child_pid, SIGTERM);
> +
> + tpebs_delete();
> +
> return COUNTER_FATAL;
> }
>
> diff --git a/tools/perf/util/Build b/tools/perf/util/Build
> index 0f18fe81ef0b..25cae5c613ad 100644
> --- a/tools/perf/util/Build
> +++ b/tools/perf/util/Build
> @@ -154,6 +154,7 @@ perf-util-y += clockid.o
> perf-util-y += list_sort.o
> perf-util-y += mutex.o
> perf-util-y += sharded_mutex.o
> +perf-util-$(CONFIG_X86_64) += intel-tpebs.o
>
> perf-util-$(CONFIG_LIBBPF) += bpf_map.o
> perf-util-$(CONFIG_PERF_BPF_SKEL) += bpf_counter.o
> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> index 3a719edafc7a..78ce80f227aa 100644
> --- a/tools/perf/util/evlist.c
> +++ b/tools/perf/util/evlist.c
> @@ -33,6 +33,7 @@
> #include "util/bpf-filter.h"
> #include "util/stat.h"
> #include "util/util.h"
> +#include "util/intel-tpebs.h"
> #include <signal.h>
> #include <unistd.h>
> #include <sched.h>
> @@ -179,6 +180,7 @@ void evlist__delete(struct evlist *evlist)
> if (evlist == NULL)
> return;
>
> + tpebs_delete();
> evlist__free_stats(evlist);
> evlist__munmap(evlist);
> evlist__close(evlist);
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index bc603193c477..1d000fa2c6cf 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -1554,6 +1554,60 @@ static void evsel__set_count(struct evsel *counter, int cpu_map_idx, int thread,
> perf_counts__set_loaded(counter->counts, cpu_map_idx, thread, true);
> }
>
> +static bool evsel__group_has_tpebs(struct evsel *leader)
> +{
> + struct evsel *evsel;
> +
> + for_each_group_evsel(evsel, leader) {
> + if (evsel__is_retire_lat(evsel))
> + return true;
> + }
> + return false;
> +}
> +
> +static u64 evsel__group_read_nr_members(struct evsel *leader)
> +{
> + u64 nr = leader->core.nr_members;
> + struct evsel *evsel;
> +
> + for_each_group_evsel(evsel, leader) {
> + if (evsel__is_retire_lat(evsel))
> + nr--;
> + }
> + return nr;
> +}
> +
> +static u64 evsel__group_read_size(struct evsel *leader)
> +{
> + u64 read_format = leader->core.attr.read_format;
> + int entry = sizeof(u64); /* value */
> + int size = 0;
> + int nr = 1;
> +
> + if (!evsel__group_has_tpebs(leader))
> + return perf_evsel__read_size(&leader->core);
> +
> + if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
> + size += sizeof(u64);
> +
> + if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
> + size += sizeof(u64);
> +
> + if (read_format & PERF_FORMAT_ID)
> + entry += sizeof(u64);
> +
> + if (read_format & PERF_FORMAT_LOST)
> + entry += sizeof(u64);
> +
> + if (read_format & PERF_FORMAT_GROUP) {
> + nr = evsel__group_read_nr_members(leader);
> + size += sizeof(u64);
> + }
> +
> + size += entry * nr;
> + return size;
> +}
> +
> static int evsel__process_group_data(struct evsel *leader, int cpu_map_idx, int thread, u64 *data)
> {
> u64 read_format = leader->core.attr.read_format;
> @@ -1562,7 +1616,7 @@ static int evsel__process_group_data(struct evsel *leader, int cpu_map_idx, int
>
> nr = *data++;
>
> - if (nr != (u64) leader->core.nr_members)
> + if (nr != evsel__group_read_nr_members(leader))
> return -EINVAL;
>
> if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
> @@ -1592,7 +1646,7 @@ static int evsel__read_group(struct evsel *leader, int cpu_map_idx, int thread)
> {
> struct perf_stat_evsel *ps = leader->stats;
> u64 read_format = leader->core.attr.read_format;
> - int size = perf_evsel__read_size(&leader->core);
> + int size = evsel__group_read_size(leader);
> u64 *data = ps->group_data;
>
> if (!(read_format & PERF_FORMAT_ID))
> @@ -2200,6 +2254,9 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
> return 0;
> }
>
> + if (evsel__is_retire_lat(evsel))
> + return tpebs_start(evsel->evlist);
> +
> err = __evsel__prepare_open(evsel, cpus, threads);
> if (err)
> return err;
> @@ -2392,6 +2449,8 @@ int evsel__open(struct evsel *evsel, struct perf_cpu_map *cpus,
>
> void evsel__close(struct evsel *evsel)
> {
> + if (evsel__is_retire_lat(evsel))
> + tpebs_delete();
> perf_evsel__close(&evsel->core);
> perf_evsel__free_id(&evsel->core);
> }
> @@ -3357,6 +3416,9 @@ static int store_evsel_ids(struct evsel *evsel, struct evlist *evlist)
> {
> int cpu_map_idx, thread;
>
> + if (evsel__is_retire_lat(evsel))
> + return 0;
> +
> for (cpu_map_idx = 0; cpu_map_idx < xyarray__max_x(evsel->core.fd); cpu_map_idx++) {
> for (thread = 0; thread < xyarray__max_y(evsel->core.fd);
> thread++) {
> diff --git a/tools/perf/util/intel-tpebs.c b/tools/perf/util/intel-tpebs.c
> new file mode 100644
> index 000000000000..6680ef887961
> --- /dev/null
> +++ b/tools/perf/util/intel-tpebs.c
> @@ -0,0 +1,430 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * intel_tpebs.c: Intel TPEBS support
> + */
> +
> +
> +#include <sys/param.h>
> +#include <subcmd/run-command.h>
> +#include <thread.h>
> +#include "intel-tpebs.h"
> +#include <linux/list.h>
> +#include <linux/zalloc.h>
> +#include <linux/err.h>
> +#include "sample.h"
> +#include "debug.h"
> +#include "evlist.h"
> +#include "evsel.h"
> +#include "session.h"
> +#include "tool.h"
> +#include "cpumap.h"
> +#include "metricgroup.h"
> +#include <sys/stat.h>
> +#include <sys/file.h>
> +#include <poll.h>
> +#include <math.h>
> +
> +#define PERF_DATA "-"
> +
> +bool tpebs_recording;
> +static pid_t tpebs_pid = -1;
> +static size_t tpebs_event_size;
> +static LIST_HEAD(tpebs_results);
> +static pthread_t tpebs_reader_thread;
> +static struct child_process *tpebs_cmd;
> +
> +struct tpebs_retire_lat {
> + struct list_head nd;
> + /* Event name */
> + const char *name;
> + /* Event name with the TPEBS modifier R */
> + const char *tpebs_name;
> + /* Count of retire_latency values found in sample data */
> + size_t count;
> + /* Sum of all the retire_latency values in sample data */
> + int sum;
> + /* Average of retire_latency, val = sum / count */
> + double val;
> +};
> +
> +static int get_perf_record_args(const char **record_argv, char buf[],
> + const char *cpumap_buf)
> +{
> + struct tpebs_retire_lat *e;
> + int i = 0;
> +
> + pr_debug("tpebs: Prepare perf record for retire_latency\n");
> +
> + record_argv[i++] = "perf";
> + record_argv[i++] = "record";
> + record_argv[i++] = "-W";
> + record_argv[i++] = "--synth=no";
> + record_argv[i++] = buf;
> +
> + if (!cpumap_buf) {
> + pr_err("tpebs: Require cpumap list to run sampling\n");
> + return -ECANCELED;
> + }
> + /* Use -C when cpumap_buf is not "-1" */
> + if (strcmp(cpumap_buf, "-1")) {
> + record_argv[i++] = "-C";
> + record_argv[i++] = cpumap_buf;
> + }
> +
> + list_for_each_entry(e, &tpebs_results, nd) {
> + record_argv[i++] = "-e";
> + record_argv[i++] = e->name;
> + }
> +
> + record_argv[i++] = "-o";
> + record_argv[i++] = PERF_DATA;
> +
> + return 0;
> +}
> +
> +static int prepare_run_command(const char **argv)
> +{
> + tpebs_cmd = zalloc(sizeof(struct child_process));
> + if (!tpebs_cmd)
> + return -ENOMEM;
> + tpebs_cmd->argv = argv;
> + tpebs_cmd->out = -1;
> + return 0;
> +}
> +
> +static int start_perf_record(int control_fd[], int ack_fd[],
> + const char *cpumap_buf)
> +{
> + const char **record_argv;
> + int ret;
> + char buf[32];
> +
> + scnprintf(buf, sizeof(buf), "--control=fd:%d,%d", control_fd[0], ack_fd[1]);
> +
> + record_argv = calloc(12 + 2 * tpebs_event_size, sizeof(char *));
> + if (!record_argv)
> + return -ENOMEM;
> +
> + ret = get_perf_record_args(record_argv, buf, cpumap_buf);
> + if (ret)
> + goto out;
> +
> + ret = prepare_run_command(record_argv);
> + if (ret)
> + goto out;
> + ret = start_command(tpebs_cmd);
> +out:
> + free(record_argv);
> + return ret;
> +}
> +
> +static int process_sample_event(struct perf_tool *tool __maybe_unused,
> + union perf_event *event __maybe_unused,
> + struct perf_sample *sample,
> + struct evsel *evsel,
> + struct machine *machine __maybe_unused)
> +{
> + int ret = 0;
> + const char *evname;
> + struct tpebs_retire_lat *t;
> +
> + evname = evsel__name(evsel);
> +
> + /*
> + * Need to handle per core results? We are assuming average retire
> + * latency value will be used. Save the number of samples and the sum of
> + * retire latency value for each event.
> + */
> + list_for_each_entry(t, &tpebs_results, nd) {
> + if (!strcmp(evname, t->name)) {
> + t->count += 1;
> + t->sum += sample->retire_lat;
> + t->val = (double) t->sum / t->count;
> + break;
> + }
> + }
> +
> + return ret;
> +}
> +
> +static int process_feature_event(struct perf_session *session,
> + union perf_event *event)
> +{
> + if (event->feat.feat_id < HEADER_LAST_FEATURE)
> + return perf_event__process_feature(session, event);
> + return 0;
> +}
> +
> +static void *__sample_reader(void *arg)
> +{
> + struct child_process *child = arg;
> + struct perf_session *session;
> + struct perf_data data = {
> + .mode = PERF_DATA_MODE_READ,
> + .path = PERF_DATA,
> + .file.fd = child->out,
> + };
> + struct perf_tool tool = {
> + .sample = process_sample_event,
> + .feature = process_feature_event,
> + .attr = perf_event__process_attr,
> + };
> +
> + session = perf_session__new(&data, &tool);
> + if (IS_ERR(session))
> + return NULL;
> + perf_session__process_events(session);
> + perf_session__delete(session);
> +
> + return NULL;
> +}
> +
> +/*
> + * tpebs_stop - stop the sample data read thread and the perf record process.
> + */
> +static int tpebs_stop(void)
> +{
> + int ret = 0;
> +
> + /* Like tpebs_start, we should only run tpebs_end once. */
> + if (tpebs_pid != -1) {
> + kill(tpebs_cmd->pid, SIGTERM);
> + tpebs_pid = -1;
> + pthread_join(tpebs_reader_thread, NULL);
> + close(tpebs_cmd->out);
> + ret = finish_command(tpebs_cmd);
> + if (ret == -ERR_RUN_COMMAND_WAITPID_SIGNAL)
> + ret = 0;
> + }
> + return ret;
> +}
> +
> +/*
> + * tpebs_start - start tpebs execution.
> + * @evsel_list: retire_latency evsels in this list will be selected and sampled
> + * to get the average retire_latency value.
> + *
> + * This function will be called from evlist level later when evlist__open() is
> + * called consistently.
> + */
> +int tpebs_start(struct evlist *evsel_list)
> +{
> + int ret = 0;
> + struct evsel *evsel;
> + char cpumap_buf[50];
> +
> + /*
> + * We should only run tpebs_start when tpebs_recording is enabled.
> + * And we should only run it once with all the required events.
> + */
> + if (tpebs_pid != -1 || !tpebs_recording)
> + return 0;
> +
> + cpu_map__snprint(evsel_list->core.user_requested_cpus, cpumap_buf, sizeof(cpumap_buf));
> + /*
> + * Prepare perf record for sampling event retire_latency before fork and
> + * prepare workload
> + */
> + evlist__for_each_entry(evsel_list, evsel) {
> + int i;
> + char *name;
> + struct tpebs_retire_lat *new;
> +
> + if (!evsel->retire_lat)
> + continue;
> +
> + pr_debug("tpebs: Retire_latency of event %s is required\n", evsel->name);
> + for (i = strlen(evsel->name) - 1; i > 0; i--) {
> + if (evsel->name[i] == 'R')
> + break;
> + }
> + if (i <= 0 || evsel->name[i] != 'R') {
> + ret = -1;
> + goto err;
> + }
> +
> + name = strdup(evsel->name);
> + if (!name) {
> + ret = -ENOMEM;
> + goto err;
> + }
> + name[i] = 'p';
> +
> + new = zalloc(sizeof(*new));
> + if (!new) {
> + ret = -1;
> + zfree(name);
> + goto err;
> + }
> + new->name = name;
> + new->tpebs_name = evsel->name;
> + list_add_tail(&new->nd, &tpebs_results);
> + tpebs_event_size += 1;
> + }
> +
> + if (tpebs_event_size > 0) {
> + 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");
> + ret = -1;
> + goto out;
> + }
> + if (pipe(ack_fd) < 0) {
> + pr_err("tpebs: Failed to create control fifo");
> + ret = -1;
> + goto out;
> + }
> +
> + ret = start_perf_record(control_fd, ack_fd, cpumap_buf);
> + if (ret)
> + goto out;
> + tpebs_pid = tpebs_cmd->pid;
> + if (pthread_create(&tpebs_reader_thread, NULL, __sample_reader, tpebs_cmd)) {
> + kill(tpebs_cmd->pid, SIGTERM);
> + close(tpebs_cmd->out);
> + pr_err("Could not create thread to process sample data.\n");
> + ret = -1;
> + goto out;
> + }
> + /* Wait for perf record initialization.*/
> + len = strlen("enable");
> + ret = write(control_fd[1], "enable", len);

Can we use EVLIST_CTL_CMD_ENABLE_TAG instead?

> + 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.
> + */

Oh, you changed it to 3 sec. But I think it's ok as we don't wait for
that long for the normal cases.

> + 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, "ack\n");

Same for 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]);
> + }
> +err:
> + if (ret)
> + tpebs_delete();
> + return ret;
> +}
> +
> +
> +int tpebs_set_evsel(struct evsel *evsel, int cpu_map_idx, int thread)
> +{
> + __u64 val;
> + bool found = false;
> + struct tpebs_retire_lat *t;
> + struct perf_counts_values *count;
> +
> + /* Non reitre_latency evsel should never enter this function. */
> + if (!evsel__is_retire_lat(evsel))
> + return -1;
> +
> + /*
> + * 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();
> + count = perf_counts(evsel->counts, cpu_map_idx, thread);
> +
> + list_for_each_entry(t, &tpebs_results, nd) {
> + if (t->tpebs_name == evsel->name || (evsel->metric_id && !strcmp(t->tpebs_name, evsel->metric_id))) {

This line is too long, please break.

Thanks,
Namhyung

> + found = true;
> + break;
> + }
> + }
> +
> + /* Set ena and run to non-zero */
> + count->ena = count->run = 1;
> + count->lost = 0;
> +
> + if (!found) {
> + /*
> + * Set default value or 0 when retire_latency for this event is
> + * not found from sampling data (record_tpebs not set or 0
> + * sample recorded).
> + */
> + count->val = 0;
> + return 0;
> + }
> +
> + /*
> + * Only set retire_latency value to the first CPU and thread.
> + */
> + if (cpu_map_idx == 0 && thread == 0)
> + val = rint(t->val);
> + else
> + val = 0;
> +
> + count->val = val;
> + return 0;
> +}
> +
> +static void tpebs_retire_lat__delete(struct tpebs_retire_lat *r)
> +{
> + zfree(&r->name);
> + free(r);
> +}
> +
> +
> +/*
> + * tpebs_delete - delete tpebs related data and stop the created thread and
> + * process by calling tpebs_stop().
> + *
> + * This function is called from evlist_delete() and also from builtin-stat
> + * stat_handle_error(). If tpebs_start() is called from places other then perf
> + * stat, need to ensure tpebs_delete() is also called to safely free mem and
> + * close the data read thread and the forked perf record process.
> + *
> + * This function is also called in evsel__close() to be symmetric with
> + * tpebs_start() being called in evsel__open(). We will update this call site
> + * when move tpebs_start() to evlist level.
> + */
> +void tpebs_delete(void)
> +{
> + struct tpebs_retire_lat *r, *rtmp;
> +
> + if (tpebs_pid == -1)
> + return;
> +
> + tpebs_stop();
> +
> + list_for_each_entry_safe(r, rtmp, &tpebs_results, nd) {
> + list_del_init(&r->nd);
> + tpebs_retire_lat__delete(r);
> + }
> +
> + if (tpebs_cmd) {
> + free(tpebs_cmd);
> + tpebs_cmd = NULL;
> + }
> +}
> diff --git a/tools/perf/util/intel-tpebs.h b/tools/perf/util/intel-tpebs.h
> new file mode 100644
> index 000000000000..766b3fbd79f1
> --- /dev/null
> +++ b/tools/perf/util/intel-tpebs.h
> @@ -0,0 +1,35 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * intel_tpebs.h: Intel TEPBS support
> + */
> +#ifndef INCLUDE__PERF_INTEL_TPEBS_H__
> +#define INCLUDE__PERF_INTEL_TPEBS_H__
> +
> +#include "stat.h"
> +#include "evsel.h"
> +
> +#ifdef HAVE_ARCH_X86_64_SUPPORT
> +
> +extern bool tpebs_recording;
> +int tpebs_start(struct evlist *evsel_list);
> +void tpebs_delete(void);
> +int tpebs_set_evsel(struct evsel *evsel, int cpu_map_idx, int thread);
> +
> +#else
> +
> +static inline int tpebs_start(struct evlist *evsel_list __maybe_unused)
> +{
> + return 0;
> +}
> +
> +static inline void tpebs_delete(void) {};
> +
> +static inline int tpebs_set_evsel(struct evsel *evsel __maybe_unused,
> + int cpu_map_idx __maybe_unused,
> + int thread __maybe_unused)
> +{
> + return 0;
> +}
> +
> +#endif
> +#endif
> --
> 2.43.0
>