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// Mini-benchmark for creating a lot of threads.
//
// Some facts:
// a) clang -O1 takes <15ms to start N=500 threads,
// consuming ~4MB more RAM than N=1.
// b) clang -O1 -ftsan takes ~26s to start N=500 threads,
// eats 5GB more RAM than N=1 (which is somewhat expected but still a lot)
// but then it consumes ~4GB of extra memory when the threads shut down!
// (definitely not in the barrier_wait interceptor)
// Also, it takes 26s to run with N=500 vs just 1.1s to run with N=1.
#include <assert.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
pthread_barrier_t all_threads_ready;
void* Thread(void *unused) {
pthread_barrier_wait(&all_threads_ready);
return 0;
}
int main(int argc, char **argv) {
int n_threads;
if (argc == 1) {
n_threads = 100;
} else if (argc == 2) {
n_threads = atoi(argv[1]);
} else {
printf("Usage: %s n_threads\n", argv[0]);
return 1;
}
printf("%s: n_threads=%d\n", __FILE__, n_threads);
pthread_barrier_init(&all_threads_ready, NULL, n_threads + 1);
pthread_t *t = new pthread_t[n_threads];
for (int i = 0; i < n_threads; i++) {
int status = pthread_create(&t[i], 0, Thread, (void*)i);
assert(status == 0);
}
// sleep(5); // FIXME: simplify measuring the memory usage.
pthread_barrier_wait(&all_threads_ready);
for (int i = 0; i < n_threads; i++) {
pthread_join(t[i], 0);
}
// sleep(5); // FIXME: simplify measuring the memory usage.
delete [] t;
return 0;
}
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