Created
April 20, 2020 12:49
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| #define _GNU_SOURCE /* See feature_test_macros(7) */ | |
| #include <stdio.h> | |
| #include <math.h> | |
| #include <sched.h> | |
| #include <pthread.h> | |
| #include <errno.h> | |
| #include <unistd.h> | |
| double waste_time(long n) { | |
| double res = 0; | |
| long i = 0; | |
| while (i < n * 200000) { | |
| i++; | |
| res += sqrt(i); | |
| } | |
| return res; | |
| } | |
| int stick_this_thread_to_core(int core_id) { | |
| int num_cores = sysconf(_SC_NPROCESSORS_ONLN); | |
| if (core_id < 0 || core_id >= num_cores) | |
| return EINVAL; | |
| cpu_set_t cpuset; | |
| CPU_ZERO(&cpuset); | |
| CPU_SET(core_id, &cpuset); | |
| pthread_t current_thread = pthread_self(); | |
| return pthread_setaffinity_np(current_thread, sizeof(cpu_set_t), &cpuset); | |
| } | |
| int get_cpu_id_from_mask(cpu_set_t cpuset) { | |
| int num_cores = sysconf(_SC_NPROCESSORS_ONLN), i; | |
| for(i = 0; i < num_cores; ++i) | |
| if(CPU_ISSET(i, &cpuset)) | |
| return i; | |
| return -1; | |
| } | |
| void *thread_func(void *param) { | |
| double result; | |
| cpu_set_t cpuset; | |
| int cpuid; | |
| CPU_ZERO(&cpuset); | |
| printf("Sticking thread to processor 0\n"); | |
| /* bind process to processor 0 */ | |
| if(stick_this_thread_to_core(0) != 0) { | |
| perror("pthread_setaffinity_np"); | |
| } | |
| /* waste some time so the work is visible with "top" */ | |
| result = waste_time(2000); | |
| if(pthread_getaffinity_np(pthread_self(), sizeof(cpu_set_t), &cpuset) != 0) { | |
| perror("pthread_getaffinity_np"); | |
| } | |
| cpuid = get_cpu_id_from_mask(cpuset); | |
| if(cpuid == -1) { | |
| perror("get_cpu_id_from_mask"); | |
| } | |
| printf("result: %f, executed on core#: %d\n", result, cpuid); | |
| printf("Sticking thread to processor 3\n"); | |
| /* bind process to processor 0 */ | |
| if(stick_this_thread_to_core(3) != 0) { | |
| perror("pthread_setaffinity_np"); | |
| } | |
| /* waste some time so the work is visible with "top" */ | |
| result = waste_time(2000); | |
| CPU_ZERO(&cpuset); | |
| if(pthread_getaffinity_np(pthread_self(), sizeof(cpu_set_t), &cpuset) != 0) { | |
| perror("pthread_getaffinity_np"); | |
| } | |
| cpuid = get_cpu_id_from_mask(cpuset); | |
| if(cpuid == -1) { | |
| perror("get_cpu_id_from_mask"); | |
| } | |
| printf("result: %f, executed on core#: %d\n", result, cpuid); | |
| } | |
| int main(int argc, char *argv[]) { | |
| pthread_t my_thread; | |
| if (pthread_create(&my_thread, NULL, thread_func, NULL) != 0) { | |
| perror("pthread_create"); | |
| } | |
| pthread_exit(NULL); | |
| return 0; | |
| } |
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