53 lines · cpp
1// Mini-benchmark for creating a lot of threads.2//3// Some facts:4// a) clang -O1 takes <15ms to start N=500 threads,5// consuming ~4MB more RAM than N=1.6// b) clang -O1 -ftsan takes ~26s to start N=500 threads,7// eats 5GB more RAM than N=1 (which is somewhat expected but still a lot)8// but then it consumes ~4GB of extra memory when the threads shut down!9// (definitely not in the barrier_wait interceptor)10// Also, it takes 26s to run with N=500 vs just 1.1s to run with N=1.11#include <assert.h>12#include <pthread.h>13#include <stdio.h>14#include <stdlib.h>15#include <unistd.h>16 17pthread_barrier_t all_threads_ready;18 19void* Thread(void *unused) {20 pthread_barrier_wait(&all_threads_ready);21 return 0;22}23 24int main(int argc, char **argv) {25 int n_threads;26 if (argc == 1) {27 n_threads = 100;28 } else if (argc == 2) {29 n_threads = atoi(argv[1]);30 } else {31 printf("Usage: %s n_threads\n", argv[0]);32 return 1;33 }34 printf("%s: n_threads=%d\n", __FILE__, n_threads);35 36 pthread_barrier_init(&all_threads_ready, NULL, n_threads + 1);37 38 pthread_t *t = new pthread_t[n_threads];39 for (int i = 0; i < n_threads; i++) {40 int status = pthread_create(&t[i], 0, Thread, (void*)i);41 assert(status == 0);42 }43 // sleep(5); // FIXME: simplify measuring the memory usage.44 pthread_barrier_wait(&all_threads_ready);45 for (int i = 0; i < n_threads; i++) {46 pthread_join(t[i], 0);47 }48 // sleep(5); // FIXME: simplify measuring the memory usage.49 delete [] t;50 51 return 0;52}53