rtla/osnoise: Add the hist mode

The rtla osnoise hist tool collects all osnoise:sample_threshold
occurrence in a histogram, displaying the results in a user-friendly
way. The tool also allows many configurations of the osnoise tracer
and the collection of the tracer output.

Here is one example of the rtla osnoise hist tool output:
  ---------- %< ----------
 [root@f34 ~]# rtla osnoise hist --bucket-size 10 --entries 100 -c 0-8 -d 1M -r 9000 -P F:1
 # RTLA osnoise histogram
 # Time unit is microseconds (us)
 # Duration:   0 00:01:00
 Index   CPU-000   CPU-001   CPU-002   CPU-003   CPU-004   CPU-005   CPU-006   CPU-007   CPU-008
 0           430       434       352       455       440       463       467       436       484
 10           88        88        92       141       120       100       126       166       100
 20           19         7        12        22         8         8        13        13        16
 30            6         0         2         0         1         2         2         1         0
 50            0         0         0         0         0         0         1         0         0
 over:         0         0         0         0         0         0         0         0         0
 count:      543       529       458       618       569       573       609       616       600
 min:          0         0         0         0         0         0         0         0         0
 avg:          0         0         0         0         0         0         0         0         0
 max:         30        20        30        20        30        30        50        30        20
  ---------- >% ----------

Running
 - rtla osnoise hist --help

provides information about the available options.

Link: https://lkml.kernel.org/r/c68060544de89b8b62510ed91c7369f162eb465b.1639158831.git.bristot@kernel.org

Cc: Tao Zhou <tao.zhou@linux.dev>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: linux-rt-users@vger.kernel.org
Cc: linux-trace-devel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

tools/tracing/rtla/src/osnoise.c

@@ -828,7 +828,8 @@ static void osnoise_usage(void)
 		"  usage: [rtla] osnoise [MODE] ...",
 		"",
 		"  modes:",
-		"     top  - prints the summary from osnoise tracer",
+		"     top   - prints the summary from osnoise tracer",
+		"     hist  - prints a histogram of osnoise samples",
 		"",
 		"if no MODE is given, the top mode is called, passing the arguments",
 		NULL,
@@ -863,6 +864,9 @@ int osnoise_main(int argc, char *argv[])
 	} else if (strcmp(argv[1], "top") == 0) {
 		osnoise_top_main(argc-1, &argv[1]);
 		exit(0);
+	} else if (strcmp(argv[1], "hist") == 0) {
+		osnoise_hist_main(argc-1, &argv[1]);
+		exit(0);
 	}
 
 usage:

tools/tracing/rtla/src/osnoise.h

@@ -86,5 +86,6 @@ void osnoise_destroy_tool(struct osnoise_tool *top);
 struct osnoise_tool *osnoise_init_tool(char *tool_name);
 struct osnoise_tool *osnoise_init_trace_tool(char *tracer);
 
+int osnoise_hist_main(int argc, char *argv[]);
 int osnoise_top_main(int argc, char **argv);
 int osnoise_main(int argc, char **argv);

tools/tracing/rtla/src/osnoise_hist.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2021 Red Hat Inc, Daniel Bristot de Oliveira <bristot@kernel.org>
+ */
+
+#include <getopt.h>
+#include <stdlib.h>
+#include <string.h>
+#include <signal.h>
+#include <unistd.h>
+#include <errno.h>
+#include <stdio.h>
+#include <time.h>
+
+#include "utils.h"
+#include "osnoise.h"
+
+struct osnoise_hist_params {
+	char			*cpus;
+	char			*monitored_cpus;
+	char			*trace_output;
+	unsigned long long	runtime;
+	unsigned long long	period;
+	long long		stop_us;
+	long long		stop_total_us;
+	int			sleep_time;
+	int			duration;
+	int			set_sched;
+	int			output_divisor;
+	struct sched_attr	sched_param;
+
+	char			no_header;
+	char			no_summary;
+	char			no_index;
+	char			with_zeros;
+	int			bucket_size;
+	int			entries;
+};
+
+struct osnoise_hist_cpu {
+	int			*samples;
+	int			count;
+
+	unsigned long long	min_sample;
+	unsigned long long	sum_sample;
+	unsigned long long	max_sample;
+
+};
+
+struct osnoise_hist_data {
+	struct tracefs_hist	*trace_hist;
+	struct osnoise_hist_cpu	*hist;
+	int			entries;
+	int			bucket_size;
+	int			nr_cpus;
+};
+
+/*
+ * osnoise_free_histogram - free runtime data
+ */
+static void
+osnoise_free_histogram(struct osnoise_hist_data *data)
+{
+	int cpu;
+
+	/* one histogram for IRQ and one for thread, per CPU */
+	for (cpu = 0; cpu < data->nr_cpus; cpu++) {
+		if (data->hist[cpu].samples)
+			free(data->hist[cpu].samples);
+	}
+
+	/* one set of histograms per CPU */
+	if (data->hist)
+		free(data->hist);
+
+	free(data);
+}
+
+/*
+ * osnoise_alloc_histogram - alloc runtime data
+ */
+static struct osnoise_hist_data
+*osnoise_alloc_histogram(int nr_cpus, int entries, int bucket_size)
+{
+	struct osnoise_hist_data *data;
+	int cpu;
+
+	data = calloc(1, sizeof(*data));
+	if (!data)
+		return NULL;
+
+	data->entries = entries;
+	data->bucket_size = bucket_size;
+	data->nr_cpus = nr_cpus;
+
+	data->hist = calloc(1, sizeof(*data->hist) * nr_cpus);
+	if (!data->hist)
+		goto cleanup;
+
+	for (cpu = 0; cpu < nr_cpus; cpu++) {
+		data->hist[cpu].samples = calloc(1, sizeof(*data->hist->samples) * (entries + 1));
+		if (!data->hist[cpu].samples)
+			goto cleanup;
+	}
+
+	/* set the min to max */
+	for (cpu = 0; cpu < nr_cpus; cpu++)
+		data->hist[cpu].min_sample = ~0;
+
+	return data;
+
+cleanup:
+	osnoise_free_histogram(data);
+	return NULL;
+}
+
+static void osnoise_hist_update_multiple(struct osnoise_tool *tool, int cpu,
+					 unsigned long long duration, int count)
+{
+	struct osnoise_hist_params *params = tool->params;
+	struct osnoise_hist_data *data = tool->data;
+	int entries = data->entries;
+	int bucket;
+	int *hist;
+
+	if (params->output_divisor)
+		duration = duration / params->output_divisor;
+
+	if (data->bucket_size)
+		bucket = duration / data->bucket_size;
+
+	hist = data->hist[cpu].samples;
+	data->hist[cpu].count += count;
+	update_min(&data->hist[cpu].min_sample, &duration);
+	update_sum(&data->hist[cpu].sum_sample, &duration);
+	update_max(&data->hist[cpu].max_sample, &duration);
+
+	if (bucket < entries)
+		hist[bucket] += count;
+	else
+		hist[entries] += count;
+}
+
+/*
+ * osnoise_destroy_trace_hist - disable events used to collect histogram
+ */
+static void osnoise_destroy_trace_hist(struct osnoise_tool *tool)
+{
+	struct osnoise_hist_data *data = tool->data;
+
+	tracefs_hist_pause(tool->trace.inst, data->trace_hist);
+	tracefs_hist_destroy(tool->trace.inst, data->trace_hist);
+}
+
+/*
+ * osnoise_init_trace_hist - enable events used to collect histogram
+ */
+static int osnoise_init_trace_hist(struct osnoise_tool *tool)
+{
+	struct osnoise_hist_params *params = tool->params;
+	struct osnoise_hist_data *data = tool->data;
+	int bucket_size;
+	char buff[128];
+	int retval = 0;
+
+	/*
+	 * Set the size of the bucket.
+	 */
+	bucket_size = params->output_divisor * params->bucket_size;
+	snprintf(buff, sizeof(buff), "duration.buckets=%d", bucket_size);
+
+	data->trace_hist = tracefs_hist_alloc(tool->trace.tep, "osnoise", "sample_threshold",
+			buff, TRACEFS_HIST_KEY_NORMAL);
+	if (!data->trace_hist)
+		return 1;
+
+	retval = tracefs_hist_add_key(data->trace_hist, "cpu", 0);
+	if (retval)
+		goto out_err;
+
+	retval = tracefs_hist_start(tool->trace.inst, data->trace_hist);
+	if (retval)
+		goto out_err;
+
+	return 0;
+
+out_err:
+	osnoise_destroy_trace_hist(tool);
+	return 1;
+}
+
+/*
+ * osnoise_read_trace_hist - parse histogram file and file osnoise histogram
+ */
+static void osnoise_read_trace_hist(struct osnoise_tool *tool)
+{
+	struct osnoise_hist_data *data = tool->data;
+	long long cpu, counter, duration;
+	char *content, *position;
+
+	tracefs_hist_pause(tool->trace.inst, data->trace_hist);
+
+	content = tracefs_event_file_read(tool->trace.inst, "osnoise",
+					  "sample_threshold",
+					  "hist", NULL);
+	if (!content)
+		return;
+
+	position = content;
+	while (true) {
+		position = strstr(position, "duration: ~");
+		if (!position)
+			break;
+		position += strlen("duration: ~");
+		duration = get_llong_from_str(position);
+		if (duration == -1)
+			err_msg("error reading duration from histogram\n");
+
+		position = strstr(position, "cpu:");
+		if (!position)
+			break;
+		position += strlen("cpu: ");
+		cpu = get_llong_from_str(position);
+		if (cpu == -1)
+			err_msg("error reading cpu from histogram\n");
+
+		position = strstr(position, "hitcount:");
+		if (!position)
+			break;
+		position += strlen("hitcount: ");
+		counter = get_llong_from_str(position);
+		if (counter == -1)
+			err_msg("error reading counter from histogram\n");
+
+		osnoise_hist_update_multiple(tool, cpu, duration, counter);
+	}
+	free(content);
+}
+
+/*
+ * osnoise_hist_header - print the header of the tracer to the output
+ */
+static void osnoise_hist_header(struct osnoise_tool *tool)
+{
+	struct osnoise_hist_params *params = tool->params;
+	struct osnoise_hist_data *data = tool->data;
+	struct trace_seq *s = tool->trace.seq;
+	char duration[26];
+	int cpu;
+
+	if (params->no_header)
+		return;
+
+	get_duration(tool->start_time, duration, sizeof(duration));
+	trace_seq_printf(s, "# RTLA osnoise histogram\n");
+	trace_seq_printf(s, "# Time unit is %s (%s)\n",
+			params->output_divisor == 1 ? "nanoseconds" : "microseconds",
+			params->output_divisor == 1 ? "ns" : "us");
+
+	trace_seq_printf(s, "# Duration: %s\n", duration);
+
+	if (!params->no_index)
+		trace_seq_printf(s, "Index");
+
+	for (cpu = 0; cpu < data->nr_cpus; cpu++) {
+		if (params->cpus && !params->monitored_cpus[cpu])
+			continue;
+
+		if (!data->hist[cpu].count)
+			continue;
+
+		trace_seq_printf(s, "   CPU-%03d", cpu);
+	}
+	trace_seq_printf(s, "\n");
+
+	trace_seq_do_printf(s);
+	trace_seq_reset(s);
+}
+
+/*
+ * osnoise_print_summary - print the summary of the hist data to the output
+ */
+static void
+osnoise_print_summary(struct osnoise_hist_params *params,
+		       struct trace_instance *trace,
+		       struct osnoise_hist_data *data)
+{
+	int cpu;
+
+	if (params->no_summary)
+		return;
+
+	if (!params->no_index)
+		trace_seq_printf(trace->seq, "count:");
+
+	for (cpu = 0; cpu < data->nr_cpus; cpu++) {
+		if (params->cpus && !params->monitored_cpus[cpu])
+			continue;
+
+		if (!data->hist[cpu].count)
+			continue;
+
+		trace_seq_printf(trace->seq, "%9d ", data->hist[cpu].count);
+	}
+	trace_seq_printf(trace->seq, "\n");
+
+	if (!params->no_index)
+		trace_seq_printf(trace->seq, "min:  ");
+
+	for (cpu = 0; cpu < data->nr_cpus; cpu++) {
+		if (params->cpus && !params->monitored_cpus[cpu])
+			continue;
+
+		if (!data->hist[cpu].count)
+			continue;
+
+		trace_seq_printf(trace->seq, "%9llu ",	data->hist[cpu].min_sample);
+
+	}
+	trace_seq_printf(trace->seq, "\n");
+
+	if (!params->no_index)
+		trace_seq_printf(trace->seq, "avg:  ");
+
+	for (cpu = 0; cpu < data->nr_cpus; cpu++) {
+		if (params->cpus && !params->monitored_cpus[cpu])
+			continue;
+
+		if (!data->hist[cpu].count)
+			continue;
+
+		if (data->hist[cpu].count)
+			trace_seq_printf(trace->seq, "%9llu ",
+					data->hist[cpu].sum_sample / data->hist[cpu].count);
+		else
+			trace_seq_printf(trace->seq, "        - ");
+	}
+	trace_seq_printf(trace->seq, "\n");
+
+	if (!params->no_index)
+		trace_seq_printf(trace->seq, "max:  ");
+
+	for (cpu = 0; cpu < data->nr_cpus; cpu++) {
+		if (params->cpus && !params->monitored_cpus[cpu])
+			continue;
+
+		if (!data->hist[cpu].count)
+			continue;
+
+		trace_seq_printf(trace->seq, "%9llu ", data->hist[cpu].max_sample);
+
+	}
+	trace_seq_printf(trace->seq, "\n");
+	trace_seq_do_printf(trace->seq);
+	trace_seq_reset(trace->seq);
+}
+
+/*
+ * osnoise_print_stats - print data for all CPUs
+ */
+static void
+osnoise_print_stats(struct osnoise_hist_params *params, struct osnoise_tool *tool)
+{
+	struct osnoise_hist_data *data = tool->data;
+	struct trace_instance *trace = &tool->trace;
+	int bucket, cpu;
+	int total;
+
+	osnoise_hist_header(tool);
+
+	for (bucket = 0; bucket < data->entries; bucket++) {
+		total = 0;
+
+		if (!params->no_index)
+			trace_seq_printf(trace->seq, "%-6d",
+					 bucket * data->bucket_size);
+
+		for (cpu = 0; cpu < data->nr_cpus; cpu++) {
+			if (params->cpus && !params->monitored_cpus[cpu])
+				continue;
+
+			if (!data->hist[cpu].count)
+				continue;
+
+			total += data->hist[cpu].samples[bucket];
+			trace_seq_printf(trace->seq, "%9d ", data->hist[cpu].samples[bucket]);
+		}
+
+		if (total == 0 && !params->with_zeros) {
+			trace_seq_reset(trace->seq);
+			continue;
+		}
+
+		trace_seq_printf(trace->seq, "\n");
+		trace_seq_do_printf(trace->seq);
+		trace_seq_reset(trace->seq);
+	}
+
+	if (!params->no_index)
+		trace_seq_printf(trace->seq, "over: ");
+
+	for (cpu = 0; cpu < data->nr_cpus; cpu++) {
+		if (params->cpus && !params->monitored_cpus[cpu])
+			continue;
+
+		if (!data->hist[cpu].count)
+			continue;
+
+		trace_seq_printf(trace->seq, "%9d ",
+				 data->hist[cpu].samples[data->entries]);
+	}
+	trace_seq_printf(trace->seq, "\n");
+	trace_seq_do_printf(trace->seq);
+	trace_seq_reset(trace->seq);
+
+	osnoise_print_summary(params, trace, data);
+}
+
+/*
+ * osnoise_hist_usage - prints osnoise hist usage message
+ */
+static void osnoise_hist_usage(char *usage)
+{
+	int i;
+
+	static const char * const msg[] = {
+		"",
+		"  usage: rtla osnoise hist [-h] [-D] [-d s] [-p us] [-r us] [-s us] [-S us] [-t[=file]] \\",
+		"	  [-c cpu-list] [-P priority] [-b N] [-e N] [--no-header] [--no-summary] \\",
+		"	  [--no-index] [--with-zeros]",
+		"",
+		"	  -h/--help: print this menu",
+		"	  -p/--period us: osnoise period in us",
+		"	  -r/--runtime us: osnoise runtime in us",
+		"	  -s/--stop us: stop trace if a single sample is higher than the argument in us",
+		"	  -S/--stop-total us: stop trace if the total sample is higher than the argument in us",
+		"	  -c/--cpus cpu-list: list of cpus to run osnoise threads",
+		"	  -d/--duration time[s|m|h|d]: duration of the session",
+		"	  -D/--debug: print debug info",
+		"	  -t/--trace[=file]: save the stopped trace to [file|osnoise_trace.txt]",
+		"	  -b/--bucket-size N: set the histogram bucket size (default 1)",
+		"	  -e/--entries N: set the number of entries of the histogram (default 256)",
+		"	     --no-header: do not print header",
+		"	     --no-summary: do not print summary",
+		"	     --no-index: do not print index",
+		"	     --with-zeros: print zero only entries",
+		"	  -P/--priority o:prio|r:prio|f:prio|d:runtime:period: set scheduling parameters",
+		"		o:prio - use SCHED_OTHER with prio",
+		"		r:prio - use SCHED_RR with prio",
+		"		f:prio - use SCHED_FIFO with prio",
+		"		d:runtime[us|ms|s]:period[us|ms|s] - use SCHED_DEADLINE with runtime and period",
+		"						       in nanoseconds",
+		NULL,
+	};
+
+	if (usage)
+		fprintf(stderr, "%s\n", usage);
+
+	fprintf(stderr, "rtla osnoise hist: a per-cpu histogram of the OS noise (version %s)\n",
+			VERSION);
+
+	for (i = 0; msg[i]; i++)
+		fprintf(stderr, "%s\n", msg[i]);
+	exit(1);
+}
+
+/*
+ * osnoise_hist_parse_args - allocs, parse and fill the cmd line parameters
+ */
+static struct osnoise_hist_params
+*osnoise_hist_parse_args(int argc, char *argv[])
+{
+	struct osnoise_hist_params *params;
+	int retval;
+	int c;
+
+	params = calloc(1, sizeof(*params));
+	if (!params)
+		exit(1);
+
+	/* display data in microseconds */
+	params->output_divisor = 1000;
+	params->bucket_size = 1;
+	params->entries = 256;
+
+	while (1) {
+		static struct option long_options[] = {
+			{"bucket-size",		required_argument,	0, 'b'},
+			{"entries",		required_argument,	0, 'e'},
+			{"cpus",		required_argument,	0, 'c'},
+			{"debug",		no_argument,		0, 'D'},
+			{"duration",		required_argument,	0, 'd'},
+			{"help",		no_argument,		0, 'h'},
+			{"period",		required_argument,	0, 'p'},
+			{"priority",		required_argument,	0, 'P'},
+			{"runtime",		required_argument,	0, 'r'},
+			{"stop",		required_argument,	0, 's'},
+			{"stop-total",		required_argument,	0, 'S'},
+			{"trace",		optional_argument,	0, 't'},
+			{"no-header",		no_argument,		0, '0'},
+			{"no-summary",		no_argument,		0, '1'},
+			{"no-index",		no_argument,		0, '2'},
+			{"with-zeros",		no_argument,		0, '3'},
+			{0, 0, 0, 0}
+		};
+
+		/* getopt_long stores the option index here. */
+		int option_index = 0;
+
+		c = getopt_long(argc, argv, "c:b:d:e:Dhp:P:r:s:S:t::0123",
+				 long_options, &option_index);
+
+		/* detect the end of the options. */
+		if (c == -1)
+			break;
+
+		switch (c) {
+		case 'b':
+			params->bucket_size = get_llong_from_str(optarg);
+			if ((params->bucket_size == 0) || (params->bucket_size >= 1000000))
+				osnoise_hist_usage("Bucket size needs to be > 0 and <= 1000000\n");
+			break;
+		case 'c':
+			retval = parse_cpu_list(optarg, &params->monitored_cpus);
+			if (retval)
+				osnoise_hist_usage("\nInvalid -c cpu list\n");
+			params->cpus = optarg;
+			break;
+		case 'D':
+			config_debug = 1;
+			break;
+		case 'd':
+			params->duration = parse_seconds_duration(optarg);
+			if (!params->duration)
+				osnoise_hist_usage("Invalid -D duration\n");
+			break;
+		case 'e':
+			params->entries = get_llong_from_str(optarg);
+			if ((params->entries < 10) || (params->entries > 9999999))
+				osnoise_hist_usage("Entries must be > 10 and < 9999999\n");
+			break;
+		case 'h':
+		case '?':
+			osnoise_hist_usage(NULL);
+			break;
+		case 'p':
+			params->period = get_llong_from_str(optarg);
+			if (params->period > 10000000)
+				osnoise_hist_usage("Period longer than 10 s\n");
+			break;
+		case 'P':
+			retval = parse_prio(optarg, &params->sched_param);
+			if (retval == -1)
+				osnoise_hist_usage("Invalid -P priority");
+			params->set_sched = 1;
+			break;
+		case 'r':
+			params->runtime = get_llong_from_str(optarg);
+			if (params->runtime < 100)
+				osnoise_hist_usage("Runtime shorter than 100 us\n");
+			break;
+		case 's':
+			params->stop_us = get_llong_from_str(optarg);
+			break;
+		case 'S':
+			params->stop_total_us = get_llong_from_str(optarg);
+			break;
+		case 't':
+			if (optarg)
+				/* skip = */
+				params->trace_output = &optarg[1];
+			else
+				params->trace_output = "osnoise_trace.txt";
+			break;
+		case '0': /* no header */
+			params->no_header = 1;
+			break;
+		case '1': /* no summary */
+			params->no_summary = 1;
+			break;
+		case '2': /* no index */
+			params->no_index = 1;
+			break;
+		case '3': /* with zeros */
+			params->with_zeros = 1;
+			break;
+		default:
+			osnoise_hist_usage("Invalid option");
+		}
+	}
+
+	if (geteuid()) {
+		err_msg("rtla needs root permission\n");
+		exit(EXIT_FAILURE);
+	}
+
+	if (params->no_index && !params->with_zeros)
+		osnoise_hist_usage("no-index set and with-zeros not set - it does not make sense");
+
+	return params;
+}
+
+/*
+ * osnoise_hist_apply_config - apply the hist configs to the initialized tool
+ */
+static int
+osnoise_hist_apply_config(struct osnoise_tool *tool, struct osnoise_hist_params *params)
+{
+	int retval;
+
+	if (!params->sleep_time)
+		params->sleep_time = 1;
+
+	if (params->cpus) {
+		retval = osnoise_set_cpus(tool->context, params->cpus);
+		if (retval) {
+			err_msg("Failed to apply CPUs config\n");
+			goto out_err;
+		}
+	}
+
+	if (params->runtime || params->period) {
+		retval = osnoise_set_runtime_period(tool->context,
+						    params->runtime,
+						    params->period);
+		if (retval) {
+			err_msg("Failed to set runtime and/or period\n");
+			goto out_err;
+		}
+	}
+
+	if (params->stop_us) {
+		retval = osnoise_set_stop_us(tool->context, params->stop_us);
+		if (retval) {
+			err_msg("Failed to set stop us\n");
+			goto out_err;
+		}
+	}
+
+	if (params->stop_total_us) {
+		retval = osnoise_set_stop_total_us(tool->context, params->stop_total_us);
+		if (retval) {
+			err_msg("Failed to set stop total us\n");
+			goto out_err;
+		}
+	}
+
+	return 0;
+
+out_err:
+	return -1;
+}
+
+/*
+ * osnoise_init_hist - initialize a osnoise hist tool with parameters
+ */
+static struct osnoise_tool
+*osnoise_init_hist(struct osnoise_hist_params *params)
+{
+	struct osnoise_tool *tool;
+	int nr_cpus;
+
+	nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
+
+	tool = osnoise_init_tool("osnoise_hist");
+	if (!tool)
+		return NULL;
+
+	tool->data = osnoise_alloc_histogram(nr_cpus, params->entries, params->bucket_size);
+	if (!tool->data)
+		goto out_err;
+
+	tool->params = params;
+
+	return tool;
+
+out_err:
+	osnoise_destroy_tool(tool);
+	return NULL;
+}
+
+static int stop_tracing;
+static void stop_hist(int sig)
+{
+	stop_tracing = 1;
+}
+
+/*
+ * osnoise_hist_set_signals - handles the signal to stop the tool
+ */
+static void
+osnoise_hist_set_signals(struct osnoise_hist_params *params)
+{
+	signal(SIGINT, stop_hist);
+	if (params->duration) {
+		signal(SIGALRM, stop_hist);
+		alarm(params->duration);
+	}
+}
+
+int osnoise_hist_main(int argc, char *argv[])
+{
+	struct osnoise_hist_params *params;
+	struct trace_instance *trace;
+	struct osnoise_tool *record;
+	struct osnoise_tool *tool;
+	int return_value = 1;
+	int retval;
+
+	params = osnoise_hist_parse_args(argc, argv);
+	if (!params)
+		exit(1);
+
+	tool = osnoise_init_hist(params);
+	if (!tool) {
+		err_msg("Could not init osnoise hist\n");
+		goto out_exit;
+	}
+
+	retval = osnoise_hist_apply_config(tool, params);
+	if (retval) {
+		err_msg("Could not apply config\n");
+		goto out_destroy;
+	}
+
+	trace = &tool->trace;
+
+	retval = enable_osnoise(trace);
+	if (retval) {
+		err_msg("Failed to enable osnoise tracer\n");
+		goto out_destroy;
+	}
+
+	retval = osnoise_init_trace_hist(tool);
+	if (retval)
+		goto out_destroy;
+
+	if (params->set_sched) {
+		retval = set_comm_sched_attr("osnoise/", &params->sched_param);
+		if (retval) {
+			err_msg("Failed to set sched parameters\n");
+			goto out_hist;
+		}
+	}
+
+	trace_instance_start(trace);
+
+	if (params->trace_output) {
+		record = osnoise_init_trace_tool("osnoise");
+		if (!record) {
+			err_msg("Failed to enable the trace instance\n");
+			goto out_hist;
+		}
+		trace_instance_start(&record->trace);
+	}
+
+	tool->start_time = time(NULL);
+	osnoise_hist_set_signals(params);
+
+	while (!stop_tracing) {
+		sleep(params->sleep_time);
+
+		retval = tracefs_iterate_raw_events(trace->tep,
+						    trace->inst,
+						    NULL,
+						    0,
+						    collect_registered_events,
+						    trace);
+		if (retval < 0) {
+			err_msg("Error iterating on events\n");
+			goto out_hist;
+		}
+
+		if (!tracefs_trace_is_on(trace->inst))
+			break;
+	};
+
+	osnoise_read_trace_hist(tool);
+
+	osnoise_print_stats(params, tool);
+
+	return_value = 0;
+
+	if (!tracefs_trace_is_on(trace->inst)) {
+		printf("rtla timelat hit stop tracing\n");
+		if (params->trace_output) {
+			printf("  Saving trace to %s\n", params->trace_output);
+			save_trace_to_file(record->trace.inst, params->trace_output);
+		}
+	}
+
+out_hist:
+	osnoise_free_histogram(tool->data);
+out_destroy:
+	osnoise_destroy_tool(tool);
+	if (params->trace_output)
+		osnoise_destroy_tool(record);
+	free(params);
+out_exit:
+	exit(return_value);
+}