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getcpu.c
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53 lines (49 loc) · 1.47 KB
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/* https://cirosantilli.com/linux-kernel-module-cheat#getcpu */
#define _GNU_SOURCE
#include <assert.h>
#include <sched.h> /* getcpu */
#include <pthread.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
/* man getcpu says this exists since glibc 2.29, but I can't find it in Ubuntu 20.04 glibc 2.31 not even with locate
* (there is a hit under /usr/src/linux-headers-5.4.0-29/include/linux/getcpu.h but it only defines `struct getcpu_cache`
* and nothing else:
* https://stackoverflow.com/questions/23224607/how-do-i-include-linux-header-files-like-linux-getcpu-h/61774312#61774312
* Furthermore, there is already a prototype in sched.h, so we can't define our own either. */
#if 0
#include <linux/getcpu.h>
#endif
void* main_thread(void *arg) {
(void)arg;
unsigned cpu, numa;
assert(!getcpu(&cpu, &numa));
printf("%u %u\n", cpu, numa);
return NULL;
}
int main(int argc, char **argv) {
pthread_t *threads;
unsigned int nthreads, i;
if (argc > 1) {
nthreads = strtoll(argv[1], NULL, 0);
} else {
nthreads = 1;
}
threads = malloc(nthreads * sizeof(*threads));
for (i = 0; i < nthreads; ++i) {
assert(pthread_create(
&threads[i],
NULL,
main_thread,
NULL
) == 0);
}
for (i = 0; i < nthreads; ++i) {
pthread_join(threads[i], NULL);
}
free(threads);
return EXIT_SUCCESS;
}