3 files changed, 109 insertions, 2 deletions

diff --git a/src/core/support/time_posix.c b/src/core/support/time_posix.c
index 841485c4b4..a274400243 100644
--- a/src/core/support/time_posix.c
+++ b/src/core/support/time_posix.c
@@ -32,6 +32,7 @@
  */
 
 #include <grpc/support/port_platform.h>
+#include <src/core/support/time_precise.h>
 
 #ifdef GPR_POSIX_TIME
 
@@ -66,8 +67,14 @@ void gpr_time_init(void) {}
 gpr_timespec gpr_now(gpr_clock_type clock) {
   struct timespec now;
   GPR_ASSERT(clock != GPR_TIMESPAN);
-  clock_gettime(clockid_for_gpr_clock[clock], &now);
-  return gpr_from_timespec(now, clock);
+  if (clock == GPR_CLOCK_PRECISE) {
+    gpr_timespec ret;
+    gpr_precise_clock_now(&ret);
+    return ret;
+  } else {
+    clock_gettime(clockid_for_gpr_clock[clock], &now);
+    return gpr_from_timespec(now, clock);
+  }
 }
 #else
 /* For some reason Apple's OSes haven't implemented clock_gettime. */
@@ -104,6 +111,9 @@ gpr_timespec gpr_now(gpr_clock_type clock) {
       now.tv_sec = now_dbl * 1e-9;
       now.tv_nsec = now_dbl - now.tv_sec * 1e9;
       break;
+    case GPR_CLOCK_PRECISE:
+      gpr_precise_clock_now(&now);
+      break;
     case GPR_TIMESPAN:
       abort();
   }
diff --git a/src/core/support/time_precise.h b/src/core/support/time_precise.h
new file mode 100644
index 0000000000..574ebb8448
--- /dev/null
+++ b/src/core/support/time_precise.h
@@ -0,0 +1,93 @@
+/*
+ *
+ * Copyright 2015, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_SUPPORT_TIME_PRECISE_H_
+#define GRPC_CORE_SUPPORT_TIME_PRECISE_H_
+
+#include <grpc/support/sync.h>
+#include <grpc/support/time.h>
+#include <stdio.h>
+
+#ifdef GRPC_TIMERS_RDTSC
+#if defined(__i386__)
+static void gpr_get_cycle_counter(long long int *clk) {
+  long long int ret;
+  __asm__ volatile("rdtsc" : "=A"(ret));
+  *clk = ret;
+}
+
+// ----------------------------------------------------------------
+#elif defined(__x86_64__) || defined(__amd64__)
+static void gpr_get_cycle_counter(long long int *clk) {
+  unsigned long long low, high;
+  __asm__ volatile("rdtsc" : "=a"(low), "=d"(high));
+  *clk = (high << 32) | low;
+}
+#endif
+
+static gpr_once precise_clock_init = GPR_ONCE_INIT;
+static long long cycles_per_second = 0;
+static void gpr_precise_clock_init() {
+  time_t start = time(NULL);
+  gpr_precise_clock start_cycle;
+  gpr_precise_clock end_cycle;
+  while (time(NULL) == start)
+    ;
+  gpr_get_cycle_counter(&start_cycle);
+  while (time(NULL) == start + 1)
+    ;
+  gpr_get_cycle_counter(&end_cycle);
+  cycles_per_second = end_cycle - start_cycle;
+}
+
+static double grpc_precise_clock_scaling_factor() {
+  gpr_once_init(&precise_clock_init, grpc_precise_clock_init);
+  return 1e6 / cycles_per_second;
+}
+
+static void gpr_precise_clock_now(gpr_timespec *clk) {
+  long long int counter;
+  gpr_get_cycle_counter(&counter);
+  clk->clock = GPR_CLOCK_REALTIME;
+  clk->tv_sec = counter / cycles_per_second;
+  clk->tv_nsec = counter % cycles_per_second;
+}
+
+#else /* GRPC_TIMERS_RDTSC */
+static void gpr_precise_clock_now(gpr_timespec *clk) {
+  *clk = gpr_now(GPR_CLOCK_REALTIME);
+  clk->clock_type = GPR_CLOCK_PRECISE;
+}
+#endif /* GRPC_TIMERS_RDTSC */
+
+#endif /* GRPC_CORE_SUPPORT_TIME_PRECISE_ */
diff --git a/src/core/support/time_win32.c b/src/core/support/time_win32.c
index 7f64c80e27..f794855429 100644
--- a/src/core/support/time_win32.c
+++ b/src/core/support/time_win32.c
@@ -38,6 +38,7 @@
 #ifdef GPR_WIN32
 
 #include <grpc/support/time.h>
+#include <src/core/support/time_precise.h>
 #include <sys/timeb.h>
 
 static LARGE_INTEGER g_start_time;
@@ -68,6 +69,9 @@ gpr_timespec gpr_now(gpr_clock_type clock) {
       now_tv.tv_sec = (time_t)now_dbl;
       now_tv.tv_nsec = (int)((now_dbl - (double)now_tv.tv_sec) * 1e9);
       break;
+    case GPR_CLOCK_PRECISE:
+      gpr_precise_clock_now(&now_tv);
+      break;
   }
   return now_tv;
 }