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Message-ID: <aYxhtrJ8cw7SNOJy@fedora>
Date: Wed, 11 Feb 2026 08:03:00 -0300
From: Wander Lairson Costa <wander@...hat.com>
To: Costa Shulyupin <costa.shul@...hat.com>
Cc: Steven Rostedt <rostedt@...dmis.org>,
Tomas Glozar <tglozar@...hat.com>, Crystal Wood <crwood@...hat.com>,
Ivan Pravdin <ipravdin.official@...il.com>, John Kacur <jkacur@...hat.com>,
Tiezhu Yang <yangtiezhu@...ngson.cn>, linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org,
bpf@...r.kernel.org
Subject: Re: [PATCH v2 1/4] tools/rtla: Consolidate nr_cpus usage across all
tools
On Mon, Feb 09, 2026 at 11:24:33AM +0200, Costa Shulyupin wrote:
> 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.
Isn't it necessary for C23 compilers?
>
> Signed-off-by: Costa Shulyupin <costa.shul@...hat.com>
> ---
> 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 +---------
> 11 files changed, 11 insertions(+), 38 deletions(-)
>
> diff --git a/tools/tracing/rtla/src/common.c b/tools/tracing/rtla/src/common.c
> index ceff76a62a30..e4cf30a65e82 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)
> {
> @@ -135,7 +137,7 @@ 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);
> }
>
> @@ -183,6 +185,7 @@ 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 7602c5593ef5..32f9c1351209 100644
> --- a/tools/tracing/rtla/src/common.h
> +++ b/tools/tracing/rtla/src/common.h
> @@ -107,6 +107,8 @@ 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 9d70ea34807f..03ebff34fff4 100644
> --- a/tools/tracing/rtla/src/osnoise_hist.c
> +++ b/tools/tracing/rtla/src/osnoise_hist.c
> @@ -647,9 +647,6 @@ 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 d54d47947fb4..7dcd2e318205 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);
>
> @@ -495,9 +491,6 @@ 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 8f8811f7a13b..69856f677fce 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 31e66ea2b144..5766d58709eb 100644
> --- a/tools/tracing/rtla/src/timerlat_aa.c
> +++ b/tools/tracing/rtla/src/timerlat_aa.c
> @@ -1022,7 +1022,6 @@ void timerlat_aa_destroy(void)
> */
> int timerlat_aa_init(struct osnoise_tool *tool, int dump_tasks)
> {
> - 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 4e8c38a61197..841118ed84f2 100644
> --- a/tools/tracing/rtla/src/timerlat_hist.c
> +++ b/tools/tracing/rtla/src/timerlat_hist.c
> @@ -1031,9 +1031,6 @@ 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 284b74773c2b..3e395ce4fa9f 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);
>
> @@ -781,9 +777,6 @@ 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@...nel.org>
> */
> diff --git a/tools/tracing/rtla/src/utils.c b/tools/tracing/rtla/src/utils.c
> index 0da3b2470c31..8cd1b374b035 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)
> @@ -559,7 +556,6 @@ 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);
>
> @@ -567,7 +563,6 @@ 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;
> @@ -644,13 +639,10 @@ 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;
> --
> 2.52.0
>
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