tools/rtla: Consolidate nr_cpus usage across all tools

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@redhat.com>
Link: https://lore.kernel.org/r/20260306194953.2511960-2-costa.shul@redhat.com
Signed-off-by: Tomas Glozar <tglozar@redhat.com>

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, &params->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);

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))

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)

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)

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, &params->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();

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;
 

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)

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)

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;

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@kernel.org>
  */

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;

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_int_eq(parse_cpu_set("0,2", &set), 0);
+	ck_assert(CPU_ISSET(0, &set));
-		ck_assert(CPU_ISSET(0, &set));
+	ck_assert(CPU_ISSET(2, &set));
-		ck_assert(CPU_ISSET(2, &set));
-	}
 
-	if (nr_cpus > 3) {
+	ck_assert_int_eq(parse_cpu_set("0-3", &set), 0);
-		ck_assert_int_eq(parse_cpu_set("0-3", &set), 0);
+	ck_assert(CPU_ISSET(0, &set));
-		ck_assert(CPU_ISSET(0, &set));
+	ck_assert(CPU_ISSET(1, &set));
-		ck_assert(CPU_ISSET(1, &set));
+	ck_assert(CPU_ISSET(2, &set));
-		ck_assert(CPU_ISSET(2, &set));
+	ck_assert(CPU_ISSET(3, &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_int_eq(parse_cpu_set("1-3,5", &set), 0);
+	ck_assert(!CPU_ISSET(0, &set));
-		ck_assert(!CPU_ISSET(0, &set));
+	ck_assert(CPU_ISSET(1, &set));
-		ck_assert(CPU_ISSET(1, &set));
+	ck_assert(CPU_ISSET(2, &set));
-		ck_assert(CPU_ISSET(2, &set));
+	ck_assert(CPU_ISSET(3, &set));
-		ck_assert(CPU_ISSET(3, &set));
+	ck_assert(!CPU_ISSET(4, &set));
-		ck_assert(!CPU_ISSET(4, &set));
+	ck_assert(CPU_ISSET(5, &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);