[PATCH v4 1/4] tools/rtla: Consolidate nr_cpus usage across all tools
From: Costa Shulyupin
Date: Fri Mar 06 2026 - 14:54:24 EST
sysconf(_SC_NPROCESSORS_CONF) (via get_nprocs_conf) reflects
cpu_possible_mask, which is fixed at boot time, so querying it
repeatedly is unnecessary.
Replace multiple calls to sysconf(_SC_NPROCESSORS_CONF) with a single
global nr_cpus variable initialized once at startup.
`#pragma once` in timerlat_u.h is needed for pre-C23 compilers to avoid
redefinition errors.
Signed-off-by: Costa Shulyupin <costa.shul@xxxxxxxxxx>
---
tools/tracing/rtla/src/common.c | 7 +++-
tools/tracing/rtla/src/common.h | 2 +
tools/tracing/rtla/src/osnoise_hist.c | 3 --
tools/tracing/rtla/src/osnoise_top.c | 7 ----
tools/tracing/rtla/src/timerlat.c | 5 +--
tools/tracing/rtla/src/timerlat_aa.c | 1 -
tools/tracing/rtla/src/timerlat_hist.c | 3 --
tools/tracing/rtla/src/timerlat_top.c | 7 ----
tools/tracing/rtla/src/timerlat_u.c | 3 +-
tools/tracing/rtla/src/timerlat_u.h | 1 +
tools/tracing/rtla/src/utils.c | 10 +----
tools/tracing/rtla/tests/unit/unit_tests.c | 44 ++++++++++------------
12 files changed, 31 insertions(+), 62 deletions(-)
diff --git a/tools/tracing/rtla/src/common.c b/tools/tracing/rtla/src/common.c
index f310b0d59ad3..a31fbaea5da6 100644
--- a/tools/tracing/rtla/src/common.c
+++ b/tools/tracing/rtla/src/common.c
@@ -5,12 +5,14 @@
#include <signal.h>
#include <stdlib.h>
#include <string.h>
-#include <unistd.h>
#include <getopt.h>
+#include <sys/sysinfo.h>
+
#include "common.h"
struct trace_instance *trace_inst;
volatile int stop_tracing;
+int nr_cpus;
static void stop_trace(int sig)
{
@@ -165,7 +167,7 @@ common_apply_config(struct osnoise_tool *tool, struct common_params *params)
}
if (!params->cpus) {
- for (i = 0; i < sysconf(_SC_NPROCESSORS_CONF); i++)
+ for (i = 0; i < nr_cpus; i++)
CPU_SET(i, ¶ms->monitored_cpus);
}
@@ -213,6 +215,7 @@ int run_tool(struct tool_ops *ops, int argc, char *argv[])
bool stopped;
int retval;
+ nr_cpus = get_nprocs_conf();
params = ops->parse_args(argc, argv);
if (!params)
exit(1);
diff --git a/tools/tracing/rtla/src/common.h b/tools/tracing/rtla/src/common.h
index d4b3715700be..90a3c0d1dbf3 100644
--- a/tools/tracing/rtla/src/common.h
+++ b/tools/tracing/rtla/src/common.h
@@ -108,6 +108,8 @@ struct common_params {
struct timerlat_u_params user;
};
+extern int nr_cpus;
+
#define for_each_monitored_cpu(cpu, nr_cpus, common) \
for (cpu = 0; cpu < nr_cpus; cpu++) \
if (!(common)->cpus || CPU_ISSET(cpu, &(common)->monitored_cpus))
diff --git a/tools/tracing/rtla/src/osnoise_hist.c b/tools/tracing/rtla/src/osnoise_hist.c
index 5c863e7aad28..00b8c95cbf85 100644
--- a/tools/tracing/rtla/src/osnoise_hist.c
+++ b/tools/tracing/rtla/src/osnoise_hist.c
@@ -646,9 +646,6 @@ static struct osnoise_tool
*osnoise_init_hist(struct common_params *params)
{
struct osnoise_tool *tool;
- int nr_cpus;
-
- nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
tool = osnoise_init_tool("osnoise_hist");
if (!tool)
diff --git a/tools/tracing/rtla/src/osnoise_top.c b/tools/tracing/rtla/src/osnoise_top.c
index b7aed40fd216..9a6cd9a2470a 100644
--- a/tools/tracing/rtla/src/osnoise_top.c
+++ b/tools/tracing/rtla/src/osnoise_top.c
@@ -232,12 +232,8 @@ osnoise_print_stats(struct osnoise_tool *top)
{
struct osnoise_params *params = to_osnoise_params(top->params);
struct trace_instance *trace = &top->trace;
- static int nr_cpus = -1;
int i;
- if (nr_cpus == -1)
- nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
-
if (!params->common.quiet)
clear_terminal(trace->seq);
@@ -494,9 +490,6 @@ osnoise_top_apply_config(struct osnoise_tool *tool)
struct osnoise_tool *osnoise_init_top(struct common_params *params)
{
struct osnoise_tool *tool;
- int nr_cpus;
-
- nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
tool = osnoise_init_tool("osnoise_top");
if (!tool)
diff --git a/tools/tracing/rtla/src/timerlat.c b/tools/tracing/rtla/src/timerlat.c
index 9e4daed0aafc..31c921efa7c1 100644
--- a/tools/tracing/rtla/src/timerlat.c
+++ b/tools/tracing/rtla/src/timerlat.c
@@ -99,7 +99,7 @@ timerlat_apply_config(struct osnoise_tool *tool, struct timerlat_params *params)
int timerlat_enable(struct osnoise_tool *tool)
{
struct timerlat_params *params = to_timerlat_params(tool->params);
- int retval, nr_cpus, i;
+ int retval, i;
if (params->dma_latency >= 0) {
dma_latency_fd = set_cpu_dma_latency(params->dma_latency);
@@ -115,8 +115,6 @@ int timerlat_enable(struct osnoise_tool *tool)
return -1;
}
- nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
-
for_each_monitored_cpu(i, nr_cpus, ¶ms->common) {
if (save_cpu_idle_disable_state(i) < 0) {
err_msg("Could not save cpu idle state.\n");
@@ -214,7 +212,6 @@ void timerlat_analyze(struct osnoise_tool *tool, bool stopped)
void timerlat_free(struct osnoise_tool *tool)
{
struct timerlat_params *params = to_timerlat_params(tool->params);
- int nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
int i;
timerlat_aa_destroy();
diff --git a/tools/tracing/rtla/src/timerlat_aa.c b/tools/tracing/rtla/src/timerlat_aa.c
index 178de60dcef9..095483375823 100644
--- a/tools/tracing/rtla/src/timerlat_aa.c
+++ b/tools/tracing/rtla/src/timerlat_aa.c
@@ -1043,7 +1043,6 @@ void timerlat_aa_destroy(void)
*/
int timerlat_aa_init(struct osnoise_tool *tool, int dump_tasks, enum stack_format stack_format)
{
- int nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
struct timerlat_aa_context *taa_ctx;
int retval;
diff --git a/tools/tracing/rtla/src/timerlat_hist.c b/tools/tracing/rtla/src/timerlat_hist.c
index 88211e54bc9d..3ebe41eed9f6 100644
--- a/tools/tracing/rtla/src/timerlat_hist.c
+++ b/tools/tracing/rtla/src/timerlat_hist.c
@@ -1040,9 +1040,6 @@ static struct osnoise_tool
*timerlat_init_hist(struct common_params *params)
{
struct osnoise_tool *tool;
- int nr_cpus;
-
- nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
tool = osnoise_init_tool("timerlat_hist");
if (!tool)
diff --git a/tools/tracing/rtla/src/timerlat_top.c b/tools/tracing/rtla/src/timerlat_top.c
index 7a00f3844f56..4105638f45c4 100644
--- a/tools/tracing/rtla/src/timerlat_top.c
+++ b/tools/tracing/rtla/src/timerlat_top.c
@@ -442,15 +442,11 @@ timerlat_print_stats(struct osnoise_tool *top)
struct timerlat_params *params = to_timerlat_params(top->params);
struct trace_instance *trace = &top->trace;
struct timerlat_top_cpu summary;
- static int nr_cpus = -1;
int i;
if (params->common.aa_only)
return;
- if (nr_cpus == -1)
- nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
-
if (!params->common.quiet)
clear_terminal(trace->seq);
@@ -790,9 +786,6 @@ static struct osnoise_tool
*timerlat_init_top(struct common_params *params)
{
struct osnoise_tool *top;
- int nr_cpus;
-
- nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
top = osnoise_init_tool("timerlat_top");
if (!top)
diff --git a/tools/tracing/rtla/src/timerlat_u.c b/tools/tracing/rtla/src/timerlat_u.c
index ce68e39d25fd..a569fe7f93aa 100644
--- a/tools/tracing/rtla/src/timerlat_u.c
+++ b/tools/tracing/rtla/src/timerlat_u.c
@@ -16,7 +16,7 @@
#include <sys/wait.h>
#include <sys/prctl.h>
-#include "utils.h"
+#include "common.h"
#include "timerlat_u.h"
/*
@@ -131,7 +131,6 @@ static int timerlat_u_send_kill(pid_t *procs, int nr_cpus)
*/
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;
diff --git a/tools/tracing/rtla/src/timerlat_u.h b/tools/tracing/rtla/src/timerlat_u.h
index 661511908957..a692331bd1c7 100644
--- a/tools/tracing/rtla/src/timerlat_u.h
+++ b/tools/tracing/rtla/src/timerlat_u.h
@@ -1,4 +1,5 @@
// SPDX-License-Identifier: GPL-2.0
+#pragma once
/*
* Copyright (C) 2023 Red Hat Inc, Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
*/
diff --git a/tools/tracing/rtla/src/utils.c b/tools/tracing/rtla/src/utils.c
index d979159f6b70..77593718766a 100644
--- a/tools/tracing/rtla/src/utils.c
+++ b/tools/tracing/rtla/src/utils.c
@@ -19,7 +19,7 @@
#include <stdio.h>
#include <limits.h>
-#include "utils.h"
+#include "common.h"
#define MAX_MSG_LENGTH 1024
int config_debug;
@@ -119,14 +119,11 @@ int parse_cpu_set(char *cpu_list, cpu_set_t *set)
{
const char *p;
int end_cpu;
- int nr_cpus;
int cpu;
int i;
CPU_ZERO(set);
- nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
-
for (p = cpu_list; *p; ) {
cpu = atoi(p);
if (cpu < 0 || (!cpu && *p != '0') || cpu >= nr_cpus)
@@ -577,7 +574,6 @@ int save_cpu_idle_disable_state(unsigned int cpu)
unsigned int nr_states;
unsigned int state;
int disabled;
- int nr_cpus;
nr_states = cpuidle_state_count(cpu);
@@ -585,7 +581,6 @@ int save_cpu_idle_disable_state(unsigned int cpu)
return 0;
if (saved_cpu_idle_disable_state == NULL) {
- nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
saved_cpu_idle_disable_state = calloc(nr_cpus, sizeof(unsigned int *));
if (!saved_cpu_idle_disable_state)
return -1;
@@ -662,13 +657,10 @@ int restore_cpu_idle_disable_state(unsigned int cpu)
void free_cpu_idle_disable_states(void)
{
int cpu;
- int nr_cpus;
if (!saved_cpu_idle_disable_state)
return;
- nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
-
for (cpu = 0; cpu < nr_cpus; cpu++) {
free(saved_cpu_idle_disable_state[cpu]);
saved_cpu_idle_disable_state[cpu] = NULL;
diff --git a/tools/tracing/rtla/tests/unit/unit_tests.c b/tools/tracing/rtla/tests/unit/unit_tests.c
index aa53f8605e36..f3c6d89e3300 100644
--- a/tools/tracing/rtla/tests/unit/unit_tests.c
+++ b/tools/tracing/rtla/tests/unit/unit_tests.c
@@ -7,8 +7,10 @@
#include <sched.h>
#include <limits.h>
#include <unistd.h>
+#include <sys/sysinfo.h>
#include "../../src/utils.h"
+int nr_cpus;
START_TEST(test_strtoi)
{
@@ -34,35 +36,29 @@ END_TEST
START_TEST(test_parse_cpu_set)
{
cpu_set_t set;
- int nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
+ nr_cpus = 8;
ck_assert_int_eq(parse_cpu_set("0", &set), 0);
ck_assert(CPU_ISSET(0, &set));
ck_assert(!CPU_ISSET(1, &set));
- if (nr_cpus > 2) {
- ck_assert_int_eq(parse_cpu_set("0,2", &set), 0);
- ck_assert(CPU_ISSET(0, &set));
- ck_assert(CPU_ISSET(2, &set));
- }
-
- if (nr_cpus > 3) {
- ck_assert_int_eq(parse_cpu_set("0-3", &set), 0);
- ck_assert(CPU_ISSET(0, &set));
- ck_assert(CPU_ISSET(1, &set));
- ck_assert(CPU_ISSET(2, &set));
- ck_assert(CPU_ISSET(3, &set));
- }
-
- if (nr_cpus > 5) {
- ck_assert_int_eq(parse_cpu_set("1-3,5", &set), 0);
- ck_assert(!CPU_ISSET(0, &set));
- ck_assert(CPU_ISSET(1, &set));
- ck_assert(CPU_ISSET(2, &set));
- ck_assert(CPU_ISSET(3, &set));
- ck_assert(!CPU_ISSET(4, &set));
- ck_assert(CPU_ISSET(5, &set));
- }
+ ck_assert_int_eq(parse_cpu_set("0,2", &set), 0);
+ ck_assert(CPU_ISSET(0, &set));
+ ck_assert(CPU_ISSET(2, &set));
+
+ ck_assert_int_eq(parse_cpu_set("0-3", &set), 0);
+ ck_assert(CPU_ISSET(0, &set));
+ ck_assert(CPU_ISSET(1, &set));
+ ck_assert(CPU_ISSET(2, &set));
+ ck_assert(CPU_ISSET(3, &set));
+
+ ck_assert_int_eq(parse_cpu_set("1-3,5", &set), 0);
+ ck_assert(!CPU_ISSET(0, &set));
+ ck_assert(CPU_ISSET(1, &set));
+ ck_assert(CPU_ISSET(2, &set));
+ ck_assert(CPU_ISSET(3, &set));
+ ck_assert(!CPU_ISSET(4, &set));
+ ck_assert(CPU_ISSET(5, &set));
ck_assert_int_eq(parse_cpu_set("-1", &set), 1);
ck_assert_int_eq(parse_cpu_set("abc", &set), 1);
--
2.53.0