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