1 files changed, 52 insertions, 0 deletions
diff --git a/lib/tsan/benchmarks/start_many_threads.cc b/lib/tsan/benchmarks/start_many_threads.cc
new file mode 100644
index 000000000000..1e86fa6c502e
--- /dev/null
+++ b/lib/tsan/benchmarks/start_many_threads.cc
@@ -0,0 +1,52 @@
+// 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;
+}