--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/cpu/x86/rdtsc_x86.cpp Tue May 15 20:24:34 2018 +0200
@@ -0,0 +1,210 @@
+/*
+ * Copyright (c) 2013, 2018, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "rdtsc_x86.hpp"
+#include "runtime/thread.inline.hpp"
+#include "vm_version_ext_x86.hpp"
+
+// The following header contains the implementations of rdtsc()
+#include OS_CPU_HEADER_INLINE(os)
+
+static jlong _epoch = 0;
+static bool rdtsc_elapsed_counter_enabled = false;
+static jlong tsc_frequency = 0;
+
+static jlong set_epoch() {
+ assert(0 == _epoch, "invariant");
+ _epoch = os::rdtsc();
+ return _epoch;
+}
+
+// Base loop to estimate ticks frequency for tsc counter from user mode.
+// Volatiles and sleep() are used to prevent compiler from applying optimizations.
+static void do_time_measurements(volatile jlong& time_base,
+ volatile jlong& time_fast,
+ volatile jlong& time_base_elapsed,
+ volatile jlong& time_fast_elapsed) {
+ static const unsigned int FT_SLEEP_MILLISECS = 1;
+ const unsigned int loopcount = 3;
+
+ volatile jlong start = 0;
+ volatile jlong fstart = 0;
+ volatile jlong end = 0;
+ volatile jlong fend = 0;
+
+ // Figure out the difference between rdtsc and os provided timer.
+ // base algorithm adopted from JRockit.
+ for (unsigned int times = 0; times < loopcount; times++) {
+ start = os::elapsed_counter();
+ OrderAccess::fence();
+ fstart = os::rdtsc();
+
+ // use sleep to prevent compiler from optimizing
+ os::sleep(Thread::current(), FT_SLEEP_MILLISECS, true);
+
+ end = os::elapsed_counter();
+ OrderAccess::fence();
+ fend = os::rdtsc();
+
+ time_base += end - start;
+ time_fast += fend - fstart;
+
+ // basis for calculating the os tick start
+ // to fast time tick start offset
+ time_base_elapsed += end;
+ time_fast_elapsed += (fend - _epoch);
+ }
+
+ time_base /= loopcount;
+ time_fast /= loopcount;
+ time_base_elapsed /= loopcount;
+ time_fast_elapsed /= loopcount;
+}
+
+static jlong initialize_frequency() {
+ assert(0 == tsc_frequency, "invariant");
+ assert(0 == _epoch, "invariant");
+ const jlong initial_counter = set_epoch();
+ if (initial_counter == 0) {
+ return 0;
+ }
+ // os time frequency
+ static double os_freq = (double)os::elapsed_frequency();
+ assert(os_freq > 0, "os_elapsed frequency corruption!");
+
+ double tsc_freq = .0;
+ double os_to_tsc_conv_factor = 1.0;
+
+ // if platform supports invariant tsc,
+ // apply higher resolution and granularity for conversion calculations
+ if (VM_Version_Ext::supports_tscinv_ext()) {
+ // for invariant tsc platforms, take the maximum qualified cpu frequency
+ tsc_freq = (double)VM_Version_Ext::maximum_qualified_cpu_frequency();
+ os_to_tsc_conv_factor = tsc_freq / os_freq;
+ } else {
+ // use measurements to estimate
+ // a conversion factor and the tsc frequency
+
+ volatile jlong time_base = 0;
+ volatile jlong time_fast = 0;
+ volatile jlong time_base_elapsed = 0;
+ volatile jlong time_fast_elapsed = 0;
+
+ // do measurements to get base data
+ // on os timer and fast ticks tsc time relation.
+ do_time_measurements(time_base, time_fast, time_base_elapsed, time_fast_elapsed);
+
+ // if invalid measurements, cannot proceed
+ if (time_fast == 0 || time_base == 0) {
+ return 0;
+ }
+
+ os_to_tsc_conv_factor = (double)time_fast / (double)time_base;
+ if (os_to_tsc_conv_factor > 1) {
+ // estimate on tsc counter frequency
+ tsc_freq = os_to_tsc_conv_factor * os_freq;
+ }
+ }
+
+ if ((tsc_freq < 0) || (tsc_freq > 0 && tsc_freq <= os_freq) || (os_to_tsc_conv_factor <= 1)) {
+ // safer to run with normal os time
+ tsc_freq = .0;
+ }
+
+ // frequency of the tsc_counter
+ return (jlong)tsc_freq;
+}
+
+static bool initialize_elapsed_counter() {
+ tsc_frequency = initialize_frequency();
+ return tsc_frequency != 0 && _epoch != 0;
+}
+
+static bool ergonomics() {
+ const bool invtsc_support = Rdtsc::is_supported();
+ if (FLAG_IS_DEFAULT(UseFastUnorderedTimeStamps) && invtsc_support) {
+ FLAG_SET_ERGO(bool, UseFastUnorderedTimeStamps, true);
+ }
+
+ bool ft_enabled = UseFastUnorderedTimeStamps && invtsc_support;
+
+ if (!ft_enabled) {
+ if (UseFastUnorderedTimeStamps && VM_Version::supports_tsc()) {
+ warning("\nThe hardware does not support invariant tsc (INVTSC) register and/or cannot guarantee tsc synchronization between sockets at startup.\n"\
+ "Values returned via rdtsc() are not guaranteed to be accurate, esp. when comparing values from cross sockets reads. Enabling UseFastUnorderedTimeStamps on non-invariant tsc hardware should be considered experimental.\n");
+ ft_enabled = true;
+ }
+ }
+
+ if (!ft_enabled) {
+ // Warn if unable to support command-line flag
+ if (UseFastUnorderedTimeStamps && !VM_Version::supports_tsc()) {
+ warning("Ignoring UseFastUnorderedTimeStamps, hardware does not support normal tsc");
+ }
+ }
+
+ return ft_enabled;
+}
+
+bool Rdtsc::is_supported() {
+ return VM_Version_Ext::supports_tscinv_ext();
+}
+
+bool Rdtsc::is_elapsed_counter_enabled() {
+ return rdtsc_elapsed_counter_enabled;
+}
+
+jlong Rdtsc::frequency() {
+ return tsc_frequency;
+}
+
+jlong Rdtsc::elapsed_counter() {
+ return os::rdtsc() - _epoch;
+}
+
+jlong Rdtsc::epoch() {
+ return _epoch;
+}
+
+jlong Rdtsc::raw() {
+ return os::rdtsc();
+}
+
+bool Rdtsc::initialize() {
+ static bool initialized = false;
+ if (!initialized) {
+ assert(!rdtsc_elapsed_counter_enabled, "invariant");
+ VM_Version_Ext::initialize();
+ assert(0 == tsc_frequency, "invariant");
+ assert(0 == _epoch, "invariant");
+ bool result = initialize_elapsed_counter(); // init hw
+ if (result) {
+ result = ergonomics(); // check logical state
+ }
+ rdtsc_elapsed_counter_enabled = result;
+ initialized = true;
+ }
+ return rdtsc_elapsed_counter_enabled;
+}