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diff --git a/src/core/support/time_precise.h b/src/core/support/time_precise.h
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+/*
+ *
+ * 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_ */