Re: [RFC PATCH v11 3/8] perf stat: Fork and launch perf record when perf stat needs to get retire latency value for a metric.

[Namhyung Kim]

Hello,

On Wed, Jun 05, 2024 at 01:21:44AM -0400, weilin.wang@xxxxxxxxx wrote:
> From: Weilin Wang <weilin.wang@xxxxxxxxx>
> 
> 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@xxxxxxxxx>
> ---
>  tools/perf/builtin-stat.c     |   6 +
>  tools/perf/util/Build         |   1 +
>  tools/perf/util/evsel.c       |  66 +++++-
>  tools/perf/util/intel-tpebs.c | 397 ++++++++++++++++++++++++++++++++++
>  tools/perf/util/intel-tpebs.h |  48 ++++
>  5 files changed, 516 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 428e9721b908..b09cb2c6e9c2 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>
> @@ -653,6 +654,9 @@ static enum counter_recovery stat_handle_error(struct evsel *counter)
>  
>  	if (child_pid != -1)
>  		kill(child_pid, SIGTERM);
> +
> +	tpebs_stop_delete();
> +
>  	return COUNTER_FATAL;
>  }
>  
> @@ -985,6 +989,8 @@ static void sig_atexit(void)
>  	if (child_pid != -1)
>  		kill(child_pid, SIGTERM);
>  
> +	tpebs_stop();
> +
>  	sigprocmask(SIG_SETMASK, &oset, NULL);
>  
>  	if (signr == -1)
> diff --git a/tools/perf/util/Build b/tools/perf/util/Build
> index 292170a99ab6..79adf39e0d8f 100644
> --- a/tools/perf/util/Build
> +++ b/tools/perf/util/Build
> @@ -153,6 +153,7 @@ perf-y += clockid.o
>  perf-y += list_sort.o
>  perf-y += mutex.o
>  perf-y += sharded_mutex.o
> +perf-$(CONFIG_X86_64) += intel-tpebs.o
>  
>  perf-$(CONFIG_LIBBPF) += bpf_map.o
>  perf-$(CONFIG_PERF_BPF_SKEL) += bpf_counter.o
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index a0a8aee7d6b9..bd3627819afe 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -1538,6 +1538,60 @@ 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;
> @@ -1546,7 +1600,7 @@ 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)
> @@ -1576,7 +1630,7 @@ 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))
> @@ -2186,6 +2240,9 @@ 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, cpus);

As it works with evlist, I think it's better to put this code there.
But it seems perf stat doesn't call the evlist API for open, then we
can add this to somewhere in __run_perf_stat() directly.

> +
>  	err = __evsel__prepare_open(evsel, cpus, threads);
>  	if (err)
>  		return err;
> @@ -2376,6 +2433,8 @@ 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();

Ditto.

>  	perf_evsel__close(&evsel->core);
>  	perf_evsel__free_id(&evsel->core);
>  }
> @@ -3341,6 +3400,9 @@ 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..37b7a4f92dd9
> --- /dev/null
> +++ b/tools/perf/util/intel-tpebs.c
> @@ -0,0 +1,397 @@
> +// 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 pthread_t tpebs_reader_thread;
> +static struct child_process *tpebs_cmd;
> +static struct list_head tpebs_results = LIST_HEAD_INIT(tpebs_results);

It can be 'static LIST_HEAD(tpebs_results);'

> +
> +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("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) {
> +		record_argv[i++] = "-C";
> +		record_argv[i++] = cpumap_buf;
> +	}
> +
> +	record_argv[i++] = "-a";
> +
> +	if (!cpumap_buf) {
> +		pr_err("Require cpumap list to run sampling.\n");
> +		return -ECANCELED;
> +	}

Hmm.. I thought you supported system wide collection, not sure if it has
a cpumap.  Anyway this check makes the earlier one meaningless - you
need the cpumap always, right?

> +
> +	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;
> +}
> +
> +int tpebs_start(struct evlist *evsel_list, struct perf_cpu_map *cpus)
> +{
> +	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(cpus, cpumap_buf, sizeof(cpumap_buf));
> +	pr_debug("cpu map: %s\n", cpumap_buf);

Can you please remove unnecessary debug prints?  If you really want it,
then make it more meaningful like with more context.

> +
> +	/*
> +	 * Prepare perf record for sampling event retire_latency before fork and
> +	 * prepare workload
> +	 */
> +	evlist__for_each_entry(evsel_list, evsel) {
> +		struct tpebs_retire_lat *new = zalloc(sizeof(*new));
> +		char *name;
> +		int i;
> +
> +		if (!evsel->retire_lat)
> +			continue;

Please move the allocation after this.

> +
> +		pr_debug("perf stat retire latency of event %s required\n", evsel->name);
> +		if (!new) {
> +			ret = -1;
> +			goto err;
> +		}
> +		for (i = strlen(evsel->name) - 1; i > 0; i--) {
> +			if (evsel->name[i] == 'R')
> +				break;

I think you also need to check ':' or '/'..

> +		}
> +		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->name = name;
> +		new->tpebs_name = strdup(evsel->name);
> +		if (!new->tpebs_name) {
> +			ret = -ENOMEM;
> +			goto err;

This error handling (including above) will leak 'new' because it's not
linked to the list yet.

> +		}
> +		list_add_tail(&new->nd, &tpebs_results);
> +		tpebs_event_size += 1;
> +	}
> +
> +	if (tpebs_event_size > 0) {
> +		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("Failed to create control fifo");
> +			ret = -1;
> +			goto out;
> +		}
> +		if (pipe(ack_fd) < 0) {
> +			pr_err("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);
> +		if (ret != len) {
> +			pr_err("perf record control write control message failed\n");
> +			goto out;
> +		}
> +
> +		ret = read(ack_fd[0], ack_buf, sizeof(ack_buf));
> +		if (ret > 0)
> +			ret = strcmp(ack_buf, "ack\n");
> +		else {
> +			pr_err("perf record control ack failed\n");
> +			goto out;
> +		}
> +		pr_debug("Received ack from perf record\n");
> +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_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;
> +}
> +
> +int tpebs_set_evsel(struct evsel *evsel, int cpu_map_idx, int thread)
> +{
> +	struct perf_counts_values *count;
> +	struct tpebs_retire_lat *t;
> +	bool found = false;
> +	__u64 val;
> +	int ret;
> +
> +	/* Non reitre_latency evsel should never enter this function. */
> +	if (!evsel__is_retire_lat(evsel))
> +		return -1;
> +
> +	ret = tpebs_stop();

I think it's better to call this in the upper layer.


> +	if (ret)
> +		return ret;
> +
> +	count = perf_counts(evsel->counts, cpu_map_idx, thread);
> +
> +	list_for_each_entry(t, &tpebs_results, nd) {
> +		if (!strcmp(t->tpebs_name, evsel->name) || !strcmp(t->tpebs_name, evsel->metric_id)) {
> +			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 (enable_tpebs_recording not set
> +		 * or 0 sample recorded).
> +		 */
> +		val = 0;

Shouldn't it set count->val to 0?

Thanks,
Namhyung


> +		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);
> +	zfree(&r->tpebs_name);
> +	free(r);
> +}
> +
> +void tpebs_delete(void)
> +{
> +	struct tpebs_retire_lat *r, *rtmp;
> +
> +	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;
> +	}
> +}
> +
> +int tpebs_stop_delete(void)
> +{
> +	int ret;
> +
> +	if (tpebs_pid == -1)
> +		return 0;
> +
> +	ret = tpebs_stop();
> +	tpebs_delete();
> +	return ret;
> +}
> diff --git a/tools/perf/util/intel-tpebs.h b/tools/perf/util/intel-tpebs.h
> new file mode 100644
> index 000000000000..73c1e5219522
> --- /dev/null
> +++ b/tools/perf/util/intel-tpebs.h
> @@ -0,0 +1,48 @@
> +/* 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, struct perf_cpu_map *cpus);
> +int tpebs_stop(void);
> +void tpebs_delete(void);
> +int tpebs_set_evsel(struct evsel *evsel, int cpu_map_idx, int thread);
> +int tpebs_stop_delete(void);
> +
> +#else
> +
> +static inline int tpebs_start(struct evlist *evsel_list __maybe_unused,
> +				struct perf_cpu_map *cpus  __maybe_unused)
> +{
> +	return 0;
> +}
> +
> +static inline int tpebs_stop(void)
> +{
> +	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;
> +}
> +
> +static inline int tpebs_stop_delete(void)
> +{
> +	return 0;
> +}
> +
> +#endif
> +#endif
> -- 
> 2.43.0
>