coroutine: add test-coroutine --benchmark-lifecycle

Add a microbenchmark for coroutine create, enter, and return (aka
lifecycle).  This is a useful benchmark because users are expected to
create many coroutines, one per I/O request for example, and we
therefore need to provide good performance in that scenario.

To run:

  make test-coroutine
  ./test-coroutine --benchmark-lifecycle 20000000

This will do 20,000,000 coroutine create, enter, return iterations and
print the resulting time.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

test-coroutine.c

@@ -150,6 +150,33 @@ static void test_lifecycle(void)
     g_assert(done); /* expect done to be true (second time) */
 }
 
+/*
+ * Lifecycle benchmark
+ */
+
+static void coroutine_fn empty_coroutine(void *opaque)
+{
+    /* Do nothing */
+}
+
+static void perf_lifecycle(void)
+{
+    Coroutine *coroutine;
+    unsigned int i, max;
+    double duration;
+
+    max = 1000000;
+
+    g_test_timer_start();
+    for (i = 0; i < max; i++) {
+        coroutine = qemu_coroutine_create(empty_coroutine);
+        qemu_coroutine_enter(coroutine, NULL);
+    }
+    duration = g_test_timer_elapsed();
+
+    g_test_message("Lifecycle %u iterations: %f s\n", max, duration);
+}
+
 int main(int argc, char **argv)
 {
     g_test_init(&argc, &argv, NULL);
@@ -158,5 +185,8 @@ int main(int argc, char **argv)
     g_test_add_func("/basic/nesting", test_nesting);
     g_test_add_func("/basic/self", test_self);
     g_test_add_func("/basic/in_coroutine", test_in_coroutine);
+    if (g_test_perf()) {
+        g_test_add_func("/perf/lifecycle", perf_lifecycle);
+    }
     return g_test_run();
 }