[for-next][PATCH 10/11] rtla/timerlat_hist: Add timerlat user-space support

From: Steven Rostedt
Date: Tue Jun 13 2023 - 18:08:54 EST

From: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>

Add the support for running timerlat threads in user-space. In this
mode, enabled with -u/--user-threads, timerlat dispatches user-space
processes that will loop in the timerlat_fd, measuring the overhead
for going to user-space and then returning to the kernel - in addition
to the existing measurements.

Here is one example of the tool's output with -u enabled:

$ sudo timerlat hist -u -c 1-3 -d 600
# RTLA timerlat histogram
# Time unit is microseconds (us)
# Duration: 0 00:10:01
Index IRQ-001 Thr-001 Usr-001 IRQ-002 Thr-002 Usr-002 IRQ-003 Thr-003 Usr-003
0 477555 0 0 425287 0 0 474357 0 0
1 122385 7998 0 174616 1921 0 125412 3138 0
2 47 587376 492150 89 594717 447830 147 593463 454872
3 11 2549 101930 7 2682 145580 64 2530 138680
4 3 1954 2833 1 463 4917 11 548 4656
5 0 60 1037 0 138 1117 6 179 1130
6 0 26 1837 0 38 277 1 76 339
7 0 15 143 0 28 147 2 37 156
8 0 10 23 0 11 75 0 12 80
9 0 7 17 0 0 26 0 11 42
10 0 2 11 0 0 18 0 2 20
11 0 0 7 0 1 8 0 2 12
12 0 0 6 0 1 4 0 2 8
13 0 1 3 0 0 0 0 0 1
14 0 1 0 0 0 1 0 0 2
15 0 1 0 0 0 0 0 0 2
16 0 1 2 0 0 0 0 0 0
17 0 0 1 0 0 0 0 0 0
19 0 0 1 0 0 0 0 0 0
over: 0 0 0 0 0 0 0 0 0
count: 600001 600001 600001 600000 600000 600000 600000 600000 600000
min: 0 1 2 0 1 2 0 1 2
avg: 0 1 2 0 2 2 0 2 2
max: 4 16 19 4 12 14 7 12 15

The tuning setup like -p or -C work for the user-space threads as well.

Link: https://lkml.kernel.org/r/b6a042d55003c4a67ff7dce28d96044b7044f00d.1686066600.git.bristot@xxxxxxxxxx

Cc: William White <chwhite@xxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Tested-by: Juri Lelli <juri.lelli@xxxxxxxxxx>
Signed-off-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
tools/tracing/rtla/src/timerlat_hist.c | 129 ++++++++++++++++++++++---
1 file changed, 118 insertions(+), 11 deletions(-)

diff --git a/tools/tracing/rtla/src/timerlat_hist.c b/tools/tracing/rtla/src/timerlat_hist.c
index f431cf43246c..47d3d8b53cb2 100644
--- a/tools/tracing/rtla/src/timerlat_hist.c
+++ b/tools/tracing/rtla/src/timerlat_hist.c
@@ -12,11 +12,13 @@
#include <stdio.h>
#include <time.h>
#include <sched.h>
+#include <pthread.h>

#include "utils.h"
#include "osnoise.h"
#include "timerlat.h"
#include "timerlat_aa.h"
+#include "timerlat_u.h"

struct timerlat_hist_params {
char *cpus;
@@ -37,6 +39,7 @@ struct timerlat_hist_params {
int hk_cpus;
int no_aa;
int dump_tasks;
+ int user_hist;
cpu_set_t hk_cpu_set;
struct sched_attr sched_param;
struct trace_events *events;
@@ -53,9 +56,11 @@ struct timerlat_hist_params {
struct timerlat_hist_cpu {
int *irq;
int *thread;
+ int *user;

int irq_count;
int thread_count;
+ int user_count;

unsigned long long min_irq;
unsigned long long sum_irq;
@@ -64,6 +69,10 @@ struct timerlat_hist_cpu {
unsigned long long min_thread;
unsigned long long sum_thread;
unsigned long long max_thread;
+
+ unsigned long long min_user;
+ unsigned long long sum_user;
+ unsigned long long max_user;
};

struct timerlat_hist_data {
@@ -88,6 +97,10 @@ timerlat_free_histogram(struct timerlat_hist_data *data)

if (data->hist[cpu].thread)
free(data->hist[cpu].thread);
+
+ if (data->hist[cpu].user)
+ free(data->hist[cpu].user);
+
}

/* one set of histograms per CPU */
@@ -124,15 +137,21 @@ static struct timerlat_hist_data
data->hist[cpu].irq = calloc(1, sizeof(*data->hist->irq) * (entries + 1));
if (!data->hist[cpu].irq)
goto cleanup;
+
data->hist[cpu].thread = calloc(1, sizeof(*data->hist->thread) * (entries + 1));
if (!data->hist[cpu].thread)
goto cleanup;
+
+ data->hist[cpu].user = calloc(1, sizeof(*data->hist->user) * (entries + 1));
+ if (!data->hist[cpu].user)
+ goto cleanup;
}

/* set the min to max */
for (cpu = 0; cpu < nr_cpus; cpu++) {
data->hist[cpu].min_irq = ~0;
data->hist[cpu].min_thread = ~0;
+ data->hist[cpu].min_user = ~0;
}

return data;
@@ -147,7 +166,7 @@ static struct timerlat_hist_data
*/
static void
timerlat_hist_update(struct osnoise_tool *tool, int cpu,
- unsigned long long thread,
+ unsigned long long context,
unsigned long long latency)
{
struct timerlat_hist_params *params = tool->params;
@@ -162,18 +181,24 @@ timerlat_hist_update(struct osnoise_tool *tool, int cpu,
if (data->bucket_size)
bucket = latency / data->bucket_size;

- if (!thread) {
+ if (!context) {
hist = data->hist[cpu].irq;
data->hist[cpu].irq_count++;
update_min(&data->hist[cpu].min_irq, &latency);
update_sum(&data->hist[cpu].sum_irq, &latency);
update_max(&data->hist[cpu].max_irq, &latency);
- } else {
+ } else if (context == 1) {
hist = data->hist[cpu].thread;
data->hist[cpu].thread_count++;
update_min(&data->hist[cpu].min_thread, &latency);
update_sum(&data->hist[cpu].sum_thread, &latency);
update_max(&data->hist[cpu].max_thread, &latency);
+ } else { /* user */
+ hist = data->hist[cpu].user;
+ data->hist[cpu].user_count++;
+ update_min(&data->hist[cpu].min_user, &latency);
+ update_sum(&data->hist[cpu].sum_user, &latency);
+ update_max(&data->hist[cpu].max_user, &latency);
}

if (bucket < entries)
@@ -190,16 +215,16 @@ timerlat_hist_handler(struct trace_seq *s, struct tep_record *record,
struct tep_event *event, void *data)
{
struct trace_instance *trace = data;
- unsigned long long thread, latency;
+ unsigned long long context, latency;
struct osnoise_tool *tool;
int cpu = record->cpu;

tool = container_of(trace, struct osnoise_tool, trace);

- tep_get_field_val(s, event, "context", record, &thread, 1);
+ tep_get_field_val(s, event, "context", record, &context, 1);
tep_get_field_val(s, event, "timer_latency", record, &latency, 1);

- timerlat_hist_update(tool, cpu, thread, latency);
+ timerlat_hist_update(tool, cpu, context, latency);

return 0;
}
@@ -241,6 +266,9 @@ static void timerlat_hist_header(struct osnoise_tool *tool)

if (!params->no_thread)
trace_seq_printf(s, " Thr-%03d", cpu);
+
+ if (params->user_hist)
+ trace_seq_printf(s, " Usr-%03d", cpu);
}
trace_seq_printf(s, "\n");

@@ -279,6 +307,10 @@ timerlat_print_summary(struct timerlat_hist_params *params,
if (!params->no_thread)
trace_seq_printf(trace->seq, "%9d ",
data->hist[cpu].thread_count);
+
+ if (params->user_hist)
+ trace_seq_printf(trace->seq, "%9d ",
+ data->hist[cpu].user_count);
}
trace_seq_printf(trace->seq, "\n");

@@ -299,6 +331,10 @@ timerlat_print_summary(struct timerlat_hist_params *params,
if (!params->no_thread)
trace_seq_printf(trace->seq, "%9llu ",
data->hist[cpu].min_thread);
+
+ if (params->user_hist)
+ trace_seq_printf(trace->seq, "%9llu ",
+ data->hist[cpu].min_user);
}
trace_seq_printf(trace->seq, "\n");

@@ -323,7 +359,15 @@ timerlat_print_summary(struct timerlat_hist_params *params,
if (!params->no_thread) {
if (data->hist[cpu].thread_count)
trace_seq_printf(trace->seq, "%9llu ",
- data->hist[cpu].sum_thread / data->hist[cpu].thread_count);
+ data->hist[cpu].sum_thread / data->hist[cpu].thread_count);
+ else
+ trace_seq_printf(trace->seq, " - ");
+ }
+
+ if (params->user_hist) {
+ if (data->hist[cpu].user_count)
+ trace_seq_printf(trace->seq, "%9llu ",
+ data->hist[cpu].sum_user / data->hist[cpu].user_count);
else
trace_seq_printf(trace->seq, " - ");
}
@@ -347,6 +391,10 @@ timerlat_print_summary(struct timerlat_hist_params *params,
if (!params->no_thread)
trace_seq_printf(trace->seq, "%9llu ",
data->hist[cpu].max_thread);
+
+ if (params->user_hist)
+ trace_seq_printf(trace->seq, "%9llu ",
+ data->hist[cpu].max_user);
}
trace_seq_printf(trace->seq, "\n");
trace_seq_do_printf(trace->seq);
@@ -392,6 +440,12 @@ timerlat_print_stats(struct timerlat_hist_params *params, struct osnoise_tool *t
data->hist[cpu].thread[bucket]);
}

+ if (params->user_hist) {
+ total += data->hist[cpu].user[bucket];
+ trace_seq_printf(trace->seq, "%9d ",
+ data->hist[cpu].user[bucket]);
+ }
+
}

if (total == 0 && !params->with_zeros) {
@@ -421,6 +475,10 @@ timerlat_print_stats(struct timerlat_hist_params *params, struct osnoise_tool *t
if (!params->no_thread)
trace_seq_printf(trace->seq, "%9d ",
data->hist[cpu].thread[data->entries]);
+
+ if (params->user_hist)
+ trace_seq_printf(trace->seq, "%9d ",
+ data->hist[cpu].user[data->entries]);
}
trace_seq_printf(trace->seq, "\n");
trace_seq_do_printf(trace->seq);
@@ -441,7 +499,7 @@ static void timerlat_hist_usage(char *usage)
" usage: [rtla] timerlat hist [-h] [-q] [-d s] [-D] [-n] [-a us] [-p us] [-i us] [-T us] [-s us] \\",
" [-t[=file]] [-e sys[:event]] [--filter <filter>] [--trigger <trigger>] [-c cpu-list] [-H cpu-list]\\",
" [-P priority] [-E N] [-b N] [--no-irq] [--no-thread] [--no-header] [--no-summary] \\",
- " [--no-index] [--with-zeros] [--dma-latency us] [-C[=cgroup_name]] [--no-aa] [--dump-task]",
+ " [--no-index] [--with-zeros] [--dma-latency us] [-C[=cgroup_name]] [--no-aa] [--dump-task] [-u]",
"",
" -h/--help: print this menu",
" -a/--auto: set automatic trace mode, stopping the session if argument in us latency is hit",
@@ -476,6 +534,7 @@ static void timerlat_hist_usage(char *usage)
" 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",
+ " -u/--user-threads: use rtla user-space threads instead of in-kernel timerlat threads",
NULL,
};

@@ -532,6 +591,7 @@ static struct timerlat_hist_params
{"stack", required_argument, 0, 's'},
{"thread", required_argument, 0, 'T'},
{"trace", optional_argument, 0, 't'},
+ {"user-threads", no_argument, 0, 'u'},
{"event", required_argument, 0, 'e'},
{"no-irq", no_argument, 0, '0'},
{"no-thread", no_argument, 0, '1'},
@@ -550,7 +610,7 @@ static struct timerlat_hist_params
/* getopt_long stores the option index here. */
int option_index = 0;

- c = getopt_long(argc, argv, "a:c:C::b:d:e:E:DhH:i:np:P:s:t::T:0123456:7:8:9\1",
+ c = getopt_long(argc, argv, "a:c:C::b:d:e:E:DhH:i:np:P:s:t::T:u0123456:7:8:9\1",
long_options, &option_index);

/* detect the end of the options. */
@@ -660,6 +720,9 @@ static struct timerlat_hist_params
else
params->trace_output = "timerlat_trace.txt";
break;
+ case 'u':
+ params->user_hist = 1;
+ break;
case '0': /* no irq */
params->no_irq = 1;
break;
@@ -744,7 +807,7 @@ static struct timerlat_hist_params
static int
timerlat_hist_apply_config(struct osnoise_tool *tool, struct timerlat_hist_params *params)
{
- int retval;
+ int retval, i;

if (!params->sleep_time)
params->sleep_time = 1;
@@ -755,6 +818,9 @@ timerlat_hist_apply_config(struct osnoise_tool *tool, struct timerlat_hist_param
err_msg("Failed to apply CPUs config\n");
goto out_err;
}
+ } else {
+ for (i = 0; i < sysconf(_SC_NPROCESSORS_CONF); i++)
+ CPU_SET(i, &params->monitored_cpus);
}

if (params->stop_us) {
@@ -807,6 +873,14 @@ timerlat_hist_apply_config(struct osnoise_tool *tool, struct timerlat_hist_param
auto_house_keeping(&params->monitored_cpus);
}

+ if (params->user_hist) {
+ retval = osnoise_set_workload(tool->context, 0);
+ if (retval) {
+ err_msg("Failed to set OSNOISE_WORKLOAD option\n");
+ goto out_err;
+ }
+ }
+
return 0;

out_err:
@@ -867,11 +941,13 @@ int timerlat_hist_main(int argc, char *argv[])
{
struct timerlat_hist_params *params;
struct osnoise_tool *record = NULL;
+ struct timerlat_u_params params_u;
struct osnoise_tool *tool = NULL;
struct osnoise_tool *aa = NULL;
struct trace_instance *trace;
int dma_latency_fd = -1;
int return_value = 1;
+ pthread_t timerlat_u;
int retval;

params = timerlat_hist_parse_args(argc, argv);
@@ -906,7 +982,7 @@ int timerlat_hist_main(int argc, char *argv[])
}
}

- if (params->cgroup) {
+ if (params->cgroup && !params->user_hist) {
retval = set_comm_cgroup("timerlat/", params->cgroup_name);
if (!retval) {
err_msg("Failed to move threads to cgroup\n");
@@ -970,6 +1046,25 @@ int timerlat_hist_main(int argc, char *argv[])
tool->start_time = time(NULL);
timerlat_hist_set_signals(params);

+ if (params->user_hist) {
+ /* rtla asked to stop */
+ params_u.should_run = 1;
+ /* all threads left */
+ params_u.stopped_running = 0;
+
+ params_u.set = &params->monitored_cpus;
+ if (params->set_sched)
+ params_u.sched_param = &params->sched_param;
+ else
+ params_u.sched_param = NULL;
+
+ params_u.cgroup_name = params->cgroup_name;
+
+ retval = pthread_create(&timerlat_u, NULL, timerlat_u_dispatcher, &params_u);
+ if (retval)
+ err_msg("Error creating timerlat user-space threads\n");
+ }
+
while (!stop_tracing) {
sleep(params->sleep_time);

@@ -986,6 +1081,18 @@ int timerlat_hist_main(int argc, char *argv[])

if (trace_is_off(&tool->trace, &record->trace))
break;
+
+ /* is there still any user-threads ? */
+ if (params->user_hist) {
+ if (params_u.stopped_running) {
+ debug_msg("timerlat user-space threads stopped!\n");
+ break;
+ }
+ }
+ }
+ if (params->user_hist && !params_u.stopped_running) {
+ params_u.should_run = 0;
+ sleep(1);
}

timerlat_print_stats(params, tool);
--
2.39.2