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-rw-r--r--lib/tsan/benchmarks/start_many_threads.cpp52
1 files changed, 52 insertions, 0 deletions
diff --git a/lib/tsan/benchmarks/start_many_threads.cpp b/lib/tsan/benchmarks/start_many_threads.cpp
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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;
+}