1 files changed, 144 insertions, 0 deletions
diff --git a/src/test/test-timers.c b/src/test/test-timers.c
new file mode 100644
index 0000000000..b5fcade7f8
--- /dev/null
+++ b/src/test/test-timers.c
@@ -0,0 +1,144 @@
+/* Copyright 2016, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#include "orconfig.h"
+
+#include <math.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <event2/event.h>
+
+#include "compat.h"
+#include "compat_libevent.h"
+#include "crypto.h"
+#include "timers.h"
+#include "util.h"
+
+#define N_TIMERS 1000
+#define MAX_DURATION 30
+#define N_DISABLE 5
+
+static struct timeval fire_at[N_TIMERS] = { {0,0} };
+static int is_disabled[N_TIMERS] = {0};
+static int fired[N_TIMERS] = {0};
+static struct timeval difference[N_TIMERS] = { {0,0} };
+static tor_timer_t *timers[N_TIMERS] = {NULL};
+
+static int n_active_timers = 0;
+static int n_fired = 0;
+
+static monotime_t started_at;
+static int64_t delay_usec[N_TIMERS];
+static int64_t diffs_mono_usec[N_TIMERS];
+
+static void
+timer_cb(tor_timer_t *t, void *arg, const monotime_t *now_mono)
+{
+  struct timeval now;
+
+  tor_gettimeofday(&now);
+  tor_timer_t **t_ptr = arg;
+  tor_assert(*t_ptr == t);
+  int idx = (int) (t_ptr - timers);
+  ++fired[idx];
+  timersub(&now, &fire_at[idx], &difference[idx]);
+  diffs_mono_usec[idx] =
+    monotime_diff_usec(&started_at, now_mono) -
+    delay_usec[idx];
+  ++n_fired;
+
+  // printf("%d / %d\n",n_fired, N_TIMERS);
+  if (n_fired == n_active_timers) {
+    event_base_loopbreak(tor_libevent_get_base());
+  }
+}
+
+int
+main(int argc, char **argv)
+{
+  (void)argc;
+  (void)argv;
+  tor_libevent_cfg cfg;
+  memset(&cfg, 0, sizeof(cfg));
+  tor_libevent_initialize(&cfg);
+  timers_initialize();
+
+  int i;
+  int ret;
+  struct timeval now;
+  tor_gettimeofday(&now);
+  monotime_get(&started_at);
+  for (i = 0; i < N_TIMERS; ++i) {
+    struct timeval delay;
+    delay.tv_sec = crypto_rand_int_range(0,MAX_DURATION);
+    delay.tv_usec = crypto_rand_int_range(0,1000000);
+    delay_usec[i] = delay.tv_sec * 1000000 + delay.tv_usec;
+    timeradd(&now, &delay, &fire_at[i]);
+    timers[i] = timer_new(timer_cb, &timers[i]);
+    timer_schedule(timers[i], &delay);
+    ++n_active_timers;
+  }
+
+  /* Disable some; we'll make sure they don't trigger. */
+  for (i = 0; i < N_DISABLE; ++i) {
+    int idx = crypto_rand_int_range(0, N_TIMERS);
+    if (is_disabled[idx])
+      continue;
+    is_disabled[idx] = 1;
+    timer_disable(timers[idx]);
+    --n_active_timers;
+  }
+
+  event_base_loop(tor_libevent_get_base(), 0);
+
+  int64_t total_difference = 0;
+  uint64_t total_square_difference = 0;
+  tor_assert(n_fired == n_active_timers);
+  for (i = 0; i < N_TIMERS; ++i) {
+    if (is_disabled[i]) {
+      tor_assert(fired[i] == 0);
+      continue;
+    }
+    tor_assert(fired[i] == 1);
+    //int64_t diff = difference[i].tv_usec + difference[i].tv_sec * 1000000;
+    int64_t diff = diffs_mono_usec[i];
+    total_difference += diff;
+    total_square_difference += diff*diff;
+  }
+  const int64_t mean_diff = total_difference / n_active_timers;
+  printf("mean difference: "I64_FORMAT" usec\n",
+         I64_PRINTF_ARG(mean_diff));
+
+  const double mean_sq = ((double)total_square_difference)/ n_active_timers;
+  const double sq_mean = mean_diff * mean_diff;
+  const double stddev = sqrt(mean_sq - sq_mean);
+  printf("standard deviation: %lf usec\n", stddev);
+
+#define MAX_DIFF_USEC (500*1000)
+#define MAX_STDDEV_USEC (500*1000)
+#define ODD_DIFF_USEC (2000)
+#define ODD_STDDEV_USEC (2000)
+
+  if (mean_diff < 0 || mean_diff > MAX_DIFF_USEC || stddev > MAX_STDDEV_USEC) {
+    printf("Either your system is under ridiculous load, or the "
+           "timer backend is broken.\n");
+    ret = 1;
+  } else if (mean_diff > ODD_DIFF_USEC || stddev > ODD_STDDEV_USEC) {
+    printf("Either your system is a bit slow or the "
+           "timer backend is odd.\n");
+    ret = 0;
+  } else {
+    printf("Looks good enough.\n");
+    ret = 0;
+  }
+
+  timer_free(NULL);
+
+  for (i = 0; i < N_TIMERS; ++i) {
+    timer_free(timers[i]);
+  }
+  timers_shutdown();
+  return ret;
+}
+