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rtla/timerlat_top: Add timerlat user-space support

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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 top -u -d 600 -q
                                       Timer Latency
    0 00:10:01   |          IRQ Timer Latency (us)        |         Thread Timer Latency (us)      |    Ret user Timer Latency (us)
  CPU COUNT      |      cur       min       avg       max |      cur       min       avg       max |      cur       min       avg       max
    0 #600001    |        0         0         0         3 |        2         1         2         9 |        3         2         3        15
    1 #600001    |        0         0         0         2 |        2         1         2        13 |        2         2         3        18
    2 #600001    |        0         0         0        10 |        2         1         2        16 |        3         2         3        20
    3 #600001    |        0         0         0         7 |        2         1         2        10 |        3         2         3        11
    4 #600000    |        0         0         0        16 |        2         1         2        41 |        3         2         3        58
    5 #600000    |        0         0         0         3 |        2         1         2        10 |        3         2         3        13
    6 #600000    |        0         0         0         5 |        2         1         2         7 |        3         2         3        10
    7 #600000    |        0         0         0         1 |        2         1         2         7 |        3         2         3        10

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

Link: https://lkml.kernel.org/r/758ad2292a0a1d884138d08219e1a0f572d257a2.1686066600.git.bristot@kernel.org

Cc: William White <chwhite@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Daniel Bristot de Oliveira 2023-06-06 18:12:23 +02:00 committed by Steven Rostedt (Google)
parent 7bc4d3089a
commit cdca4f4e5e
7 changed files with 474 additions and 6 deletions
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65
tools/tracing/rtla/src/osnoise.c
View file

@ -841,6 +841,67 @@ static void osnoise_put_irq_disable(struct osnoise_context *context)
context->orig_opt_irq_disable = OSNOISE_OPTION_INIT_VAL;
}
static int osnoise_get_workload(struct osnoise_context *context)
{
if (context->opt_workload != OSNOISE_OPTION_INIT_VAL)
return context->opt_workload;
if (context->orig_opt_workload != OSNOISE_OPTION_INIT_VAL)
return context->orig_opt_workload;
context->orig_opt_workload = osnoise_options_get_option("OSNOISE_WORKLOAD");
return context->orig_opt_workload;
}
int osnoise_set_workload(struct osnoise_context *context, bool onoff)
{
int opt_workload = osnoise_get_workload(context);
int retval;
if (opt_workload == OSNOISE_OPTION_INIT_VAL)
return -1;
if (opt_workload == onoff)
return 0;
retval = osnoise_options_set_option("OSNOISE_WORKLOAD", onoff);
if (retval < 0)
return -1;
context->opt_workload = onoff;
return 0;
}
static void osnoise_restore_workload(struct osnoise_context *context)
{
int retval;
if (context->orig_opt_workload == OSNOISE_OPTION_INIT_VAL)
return;
if (context->orig_opt_workload == context->opt_workload)
goto out_done;
retval = osnoise_options_set_option("OSNOISE_WORKLOAD", context->orig_opt_workload);
if (retval < 0)
err_msg("Could not restore original OSNOISE_WORKLOAD option\n");
out_done:
context->orig_opt_workload = OSNOISE_OPTION_INIT_VAL;
}
static void osnoise_put_workload(struct osnoise_context *context)
{
osnoise_restore_workload(context);
if (context->orig_opt_workload == OSNOISE_OPTION_INIT_VAL)
return;
context->orig_opt_workload = OSNOISE_OPTION_INIT_VAL;
}
/*
* enable_osnoise - enable osnoise tracer in the trace_instance
*/
@ -908,6 +969,9 @@ struct osnoise_context *osnoise_context_alloc(void)
context->orig_opt_irq_disable = OSNOISE_OPTION_INIT_VAL;
context->opt_irq_disable = OSNOISE_OPTION_INIT_VAL;
context->orig_opt_workload = OSNOISE_OPTION_INIT_VAL;
context->opt_workload = OSNOISE_OPTION_INIT_VAL;
osnoise_get_context(context);
return context;
@ -935,6 +999,7 @@ void osnoise_put_context(struct osnoise_context *context)
osnoise_put_print_stack(context);
osnoise_put_tracing_thresh(context);
osnoise_put_irq_disable(context);
osnoise_put_workload(context);
free(context);
}

5
tools/tracing/rtla/src/osnoise.h
View file

@ -42,6 +42,10 @@ struct osnoise_context {
/* -1 as init value because 0 is off */
int orig_opt_irq_disable;
int opt_irq_disable;
/* -1 as init value because 0 is off */
int orig_opt_workload;
int opt_workload;
};
/*
@ -84,6 +88,7 @@ int osnoise_set_print_stack(struct osnoise_context *context,
long long print_stack);
int osnoise_set_irq_disable(struct osnoise_context *context, bool onoff);
int osnoise_set_workload(struct osnoise_context *context, bool onoff);
/*
* osnoise_tool - osnoise based tool definition.

108
tools/tracing/rtla/src/timerlat_top.c
View file

@ -13,11 +13,13 @@
#include <time.h>
#include <errno.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_top_params {
char *cpus;
@ -40,6 +42,7 @@ struct timerlat_top_params {
int dump_tasks;
int cgroup;
int hk_cpus;
int user_top;
cpu_set_t hk_cpu_set;
struct sched_attr sched_param;
struct trace_events *events;
@ -48,6 +51,7 @@ struct timerlat_top_params {
struct timerlat_top_cpu {
int irq_count;
int thread_count;
int user_count;
unsigned long long cur_irq;
unsigned long long min_irq;
@ -58,6 +62,11 @@ struct timerlat_top_cpu {
unsigned long long min_thread;
unsigned long long sum_thread;
unsigned long long max_thread;
unsigned long long cur_user;
unsigned long long min_user;
unsigned long long sum_user;
unsigned long long max_user;
};
struct timerlat_top_data {
@ -98,6 +107,7 @@ static struct timerlat_top_data *timerlat_alloc_top(int nr_cpus)
for (cpu = 0; cpu < nr_cpus; cpu++) {
data->cpu_data[cpu].min_irq = ~0;
data->cpu_data[cpu].min_thread = ~0;
data->cpu_data[cpu].min_user = ~0;
}
return data;
@ -124,12 +134,18 @@ timerlat_top_update(struct osnoise_tool *tool, int cpu,
update_min(&cpu_data->min_irq, &latency);
update_sum(&cpu_data->sum_irq, &latency);
update_max(&cpu_data->max_irq, &latency);
} else {
} else if (thread == 1) {
cpu_data->thread_count++;
cpu_data->cur_thread = latency;
update_min(&cpu_data->min_thread, &latency);
update_sum(&cpu_data->sum_thread, &latency);
update_max(&cpu_data->max_thread, &latency);
} else {
cpu_data->user_count++;
cpu_data->cur_user = latency;
update_min(&cpu_data->min_user, &latency);
update_sum(&cpu_data->sum_user, &latency);
update_max(&cpu_data->max_user, &latency);
}
}
@ -172,15 +188,25 @@ static void timerlat_top_header(struct osnoise_tool *top)
trace_seq_printf(s, "\033[2;37;40m");
trace_seq_printf(s, " Timer Latency ");
if (params->user_top)
trace_seq_printf(s, " ");
trace_seq_printf(s, "\033[0;0;0m");
trace_seq_printf(s, "\n");
trace_seq_printf(s, "%-6s | IRQ Timer Latency (%s) | Thread Timer Latency (%s)\n", duration,
trace_seq_printf(s, "%-6s | IRQ Timer Latency (%s) | Thread Timer Latency (%s)", duration,
params->output_divisor == 1 ? "ns" : "us",
params->output_divisor == 1 ? "ns" : "us");
if (params->user_top) {
trace_seq_printf(s, " | Ret user Timer Latency (%s)",
params->output_divisor == 1 ? "ns" : "us");
}
trace_seq_printf(s, "\n");
trace_seq_printf(s, "\033[2;30;47m");
trace_seq_printf(s, "CPU COUNT | cur min avg max | cur min avg max");
if (params->user_top)
trace_seq_printf(s, " | cur min avg max");
trace_seq_printf(s, "\033[0;0;0m");
trace_seq_printf(s, "\n");
}
@ -233,7 +259,27 @@ static void timerlat_top_print(struct osnoise_tool *top, int cpu)
trace_seq_printf(s, "%9llu ", cpu_data->min_thread / divisor);
trace_seq_printf(s, "%9llu ",
(cpu_data->sum_thread / cpu_data->thread_count) / divisor);
trace_seq_printf(s, "%9llu\n", cpu_data->max_thread / divisor);
trace_seq_printf(s, "%9llu", cpu_data->max_thread / divisor);
}
if (!params->user_top) {
trace_seq_printf(s, "\n");
return;
}
trace_seq_printf(s, " |");
if (!cpu_data->user_count) {
trace_seq_printf(s, " - ");
trace_seq_printf(s, " - ");
trace_seq_printf(s, " - ");
trace_seq_printf(s, " -\n");
} else {
trace_seq_printf(s, "%9llu ", cpu_data->cur_user / divisor);
trace_seq_printf(s, "%9llu ", cpu_data->min_user / divisor);
trace_seq_printf(s, "%9llu ",
(cpu_data->sum_user / cpu_data->user_count) / divisor);
trace_seq_printf(s, "%9llu\n", cpu_data->max_user / divisor);
}
}
@ -288,7 +334,7 @@ static void timerlat_top_usage(char *usage)
"",
" usage: rtla timerlat [top] [-h] [-q] [-a us] [-d s] [-D] [-n] [-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] [--dma-latency us] [--aa-only us] [-C[=cgroup_name]]",
" [-P priority] [--dma-latency us] [--aa-only us] [-C[=cgroup_name]] [-u]",
"",
" -h/--help: print this menu",
" -a/--auto: set automatic trace mode, stopping the session if argument in us latency is hit",
@ -317,6 +363,7 @@ static void timerlat_top_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,
};
@ -371,6 +418,7 @@ static struct timerlat_top_params
{"stack", required_argument, 0, 's'},
{"thread", required_argument, 0, 'T'},
{"trace", optional_argument, 0, 't'},
{"user-threads", no_argument, 0, 'u'},
{"trigger", required_argument, 0, '0'},
{"filter", required_argument, 0, '1'},
{"dma-latency", required_argument, 0, '2'},
@ -383,7 +431,7 @@ static struct timerlat_top_params
/* getopt_long stores the option index here. */
int option_index = 0;
c = getopt_long(argc, argv, "a:c:C::d:De:hH:i:np:P:qs:t::T:0:1:2:345:",
c = getopt_long(argc, argv, "a:c:C::d:De:hH:i:np:P:qs:t::T:u0:1:2:345:",
long_options, &option_index);
/* detect the end of the options. */
@ -498,6 +546,9 @@ static struct timerlat_top_params
else
params->trace_output = "timerlat_trace.txt";
break;
case 'u':
params->user_top = true;
break;
case '0': /* trigger */
if (params->events) {
@ -563,6 +614,7 @@ static int
timerlat_top_apply_config(struct osnoise_tool *top, struct timerlat_top_params *params)
{
int retval;
int i;
if (!params->sleep_time)
params->sleep_time = 1;
@ -573,6 +625,9 @@ timerlat_top_apply_config(struct osnoise_tool *top, struct timerlat_top_params *
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) {
@ -627,6 +682,14 @@ timerlat_top_apply_config(struct osnoise_tool *top, struct timerlat_top_params *
auto_house_keeping(&params->monitored_cpus);
}
if (params->user_top) {
retval = osnoise_set_workload(top->context, 0);
if (retval) {
err_msg("Failed to set OSNOISE_WORKLOAD option\n");
goto out_err;
}
}
return 0;
out_err:
@ -687,10 +750,12 @@ int timerlat_top_main(int argc, char *argv[])
{
struct timerlat_top_params *params;
struct osnoise_tool *record = NULL;
struct timerlat_u_params params_u;
struct osnoise_tool *top = NULL;
struct osnoise_tool *aa = NULL;
struct trace_instance *trace;
int dma_latency_fd = -1;
pthread_t timerlat_u;
int return_value = 1;
char *max_lat;
int retval;
@ -727,7 +792,7 @@ int timerlat_top_main(int argc, char *argv[])
}
}
if (params->cgroup) {
if (params->cgroup && !params->user_top) {
retval = set_comm_cgroup("timerlat/", params->cgroup_name);
if (!retval) {
err_msg("Failed to move threads to cgroup\n");
@ -800,6 +865,25 @@ int timerlat_top_main(int argc, char *argv[])
top->start_time = time(NULL);
timerlat_top_set_signals(params);
if (params->user_top) {
/* 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);
@ -823,6 +907,18 @@ int timerlat_top_main(int argc, char *argv[])
if (trace_is_off(&top->trace, &record->trace))
break;
/* is there still any user-threads ? */
if (params->user_top) {
if (params_u.stopped_running) {
debug_msg("timerlat user space threads stopped!\n");
break;
}
}
}
if (params->user_top && !params_u.stopped_running) {
params_u.should_run = 0;
sleep(1);
}
timerlat_print_stats(params, top);

224
tools/tracing/rtla/src/timerlat_u.c Normal file
View file

@ -0,0 +1,224 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2023 Red Hat Inc, Daniel Bristot de Oliveira <bristot@kernel.org>
*/
#define _GNU_SOURCE
#include <sched.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <tracefs.h>
#include <pthread.h>
#include <sys/wait.h>
#include <sys/prctl.h>
#include "utils.h"
#include "timerlat_u.h"
/*
* This is the user-space main for the tool timerlatu/ threads.
*
* It is as simple as this:
* - set affinity
* - set priority
* - open tracer fd
* - spin
* - close
*/
static int timerlat_u_main(int cpu, struct timerlat_u_params *params)
{
struct sched_param sp = { .sched_priority = 95 };
char buffer[1024];
int timerlat_fd;
cpu_set_t set;
int retval;
/*
* This all is only setting up the tool.
*/
CPU_ZERO(&set);
CPU_SET(cpu, &set);
retval = sched_setaffinity(gettid(), sizeof(set), &set);
if (retval == -1) {
err_msg("Error setting user thread affinity\n");
exit(1);
}
if (!params->sched_param) {
retval = sched_setscheduler(0, SCHED_FIFO, &sp);
if (retval < 0) {
err_msg("Error setting timerlat u default priority: %s\n", strerror(errno));
exit(1);
}
} else {
retval = __set_sched_attr(getpid(), params->sched_param);
if (retval) {
/* __set_sched_attr prints an error message, so */
exit(0);
}
}
if (params->cgroup_name) {
retval = set_pid_cgroup(gettid(), params->cgroup_name);
if (!retval) {
err_msg("Error setting timerlat u cgroup pid\n");
pthread_exit(&retval);
}
}
/*
* This is the tool's loop. If you want to use as base for your own tool...
* go ahead.
*/
snprintf(buffer, sizeof(buffer), "osnoise/per_cpu/cpu%d/timerlat_fd", cpu);
timerlat_fd = tracefs_instance_file_open(NULL, buffer, O_RDONLY);
if (timerlat_fd < 0) {
err_msg("Error opening %s:%s\n", buffer, strerror(errno));
exit(1);
}
debug_msg("User-space timerlat pid %d on cpu %d\n", gettid(), cpu);
/* add should continue with a signal handler */
while (true) {
retval = read(timerlat_fd, buffer, 1024);
if (retval < 0)
break;
}
close(timerlat_fd);
debug_msg("Leaving timerlat pid %d on cpu %d\n", gettid(), cpu);
exit(0);
}
/*
* timerlat_u_send_kill - send a kill signal for all processes
*
* Return the number of processes that received the kill.
*/
static int timerlat_u_send_kill(pid_t *procs, int nr_cpus)
{
int killed = 0;
int i, retval;
for (i = 0; i < nr_cpus; i++) {
if (!procs[i])
continue;
retval = kill(procs[i], SIGKILL);
if (!retval)
killed++;
else
err_msg("Error killing child process %d\n", procs[i]);
}
return killed;
}
/**
* timerlat_u_dispatcher - dispatch one timerlatu/ process per monitored CPU
*
* This is a thread main that will fork one new process for each monitored
* CPU. It will wait for:
*
* - rtla to tell to kill the child processes
* - some child process to die, and the cleanup all the processes
*
* whichever comes first.
*
*/
void *timerlat_u_dispatcher(void *data)
{
int nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
struct timerlat_u_params *params = data;
char proc_name[128];
int procs_count = 0;
int retval = 1;
pid_t *procs;
int wstatus;
pid_t pid;
int i;
debug_msg("Dispatching timerlat u procs\n");
procs = calloc(nr_cpus, sizeof(pid_t));
if (!procs)
pthread_exit(&retval);
for (i = 0; i < nr_cpus; i++) {
if (params->set && !CPU_ISSET(i, params->set))
continue;
pid = fork();
/* child */
if (!pid) {
/*
* rename the process
*/
snprintf(proc_name, sizeof(proc_name), "timerlatu/%d", i);
pthread_setname_np(pthread_self(), proc_name);
prctl(PR_SET_NAME, (unsigned long)proc_name, 0, 0, 0);
timerlat_u_main(i, params);
/* timerlat_u_main should exit()! Anyways... */
pthread_exit(&retval);
}
/* parent */
if (pid == -1) {
timerlat_u_send_kill(procs, nr_cpus);
debug_msg("Failed to create child processes");
pthread_exit(&retval);
}
procs_count++;
procs[i] = pid;
}
while (params->should_run) {
/* check if processes died */
pid = waitpid(-1, &wstatus, WNOHANG);
if (pid != 0) {
for (i = 0; i < nr_cpus; i++) {
if (procs[i] == pid) {
procs[i] = 0;
procs_count--;
}
}
break;
}
sleep(1);
}
timerlat_u_send_kill(procs, nr_cpus);
while (procs_count) {
pid = waitpid(-1, &wstatus, 0);
if (pid == -1) {
err_msg("Failed to monitor child processes");
pthread_exit(&retval);
}
for (i = 0; i < nr_cpus; i++) {
if (procs[i] == pid) {
procs[i] = 0;
procs_count--;
}
}
}
params->stopped_running = 1;
free(procs);
retval = 0;
pthread_exit(&retval);
}

18
tools/tracing/rtla/src/timerlat_u.h Normal file
View file

@ -0,0 +1,18 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2023 Red Hat Inc, Daniel Bristot de Oliveira <bristot@kernel.org>
*/
struct timerlat_u_params {
/* timerlat -> timerlat_u: user-space threads can keep running */
int should_run;
/* timerlat_u -> timerlat: all timerlat_u threads left, no reason to continue */
int stopped_running;
/* threads config */
cpu_set_t *set;
char *cgroup_name;
struct sched_attr *sched_param;
};
void *timerlat_u_dispatcher(void *data);

58
tools/tracing/rtla/src/utils.c
View file

@ -626,6 +626,64 @@ static int get_self_cgroup(char *self_cg, int sizeof_self_cg)
return 1;
}
/*
* set_comm_cgroup - Set cgroup to pid_t pid
*
* If cgroup argument is not NULL, the threads will move to the given cgroup.
* Otherwise, the cgroup of the calling, i.e., rtla, thread will be used.
*
* Supports cgroup v2.
*
* Returns 1 on success, 0 otherwise.
*/
int set_pid_cgroup(pid_t pid, const char *cgroup)
{
char cgroup_path[MAX_PATH - strlen("/cgroup.procs")];
char cgroup_procs[MAX_PATH];
char pid_str[24];
int retval;
int cg_fd;
retval = find_mount("cgroup2", cgroup_path, sizeof(cgroup_path));
if (!retval) {
err_msg("Did not find cgroupv2 mount point\n");
return 0;
}
if (!cgroup) {
retval = get_self_cgroup(&cgroup_path[strlen(cgroup_path)],
sizeof(cgroup_path) - strlen(cgroup_path));
if (!retval) {
err_msg("Did not find self cgroup\n");
return 0;
}
} else {
snprintf(&cgroup_path[strlen(cgroup_path)],
sizeof(cgroup_path) - strlen(cgroup_path), "%s/", cgroup);
}
snprintf(cgroup_procs, MAX_PATH, "%s/cgroup.procs", cgroup_path);
debug_msg("Using cgroup path at: %s\n", cgroup_procs);
cg_fd = open(cgroup_procs, O_RDWR);
if (cg_fd < 0)
return 0;
snprintf(pid_str, sizeof(pid_str), "%d\n", pid);
retval = write(cg_fd, pid_str, strlen(pid_str));
if (retval < 0)
err_msg("Error setting cgroup attributes for pid:%s - %s\n",
pid_str, strerror(errno));
else
debug_msg("Set cgroup attributes for pid:%s\n", pid_str);
close(cg_fd);
return (retval >= 0);
}
/**
* set_comm_cgroup - Set cgroup to threads starting with char *comm_prefix
*

2
tools/tracing/rtla/src/utils.h
View file

@ -57,8 +57,10 @@ struct sched_attr {
int parse_prio(char *arg, struct sched_attr *sched_param);
int parse_cpu_set(char *cpu_list, cpu_set_t *set);
int __set_sched_attr(int pid, struct sched_attr *attr);
int set_comm_sched_attr(const char *comm_prefix, struct sched_attr *attr);
int set_comm_cgroup(const char *comm_prefix, const char *cgroup);
int set_pid_cgroup(pid_t pid, const char *cgroup);
int set_cpu_dma_latency(int32_t latency);
int auto_house_keeping(cpu_set_t *monitored_cpus);