jdk8-mips64-public/hotspot: src/cpu/x86/vm/rdtsc_x86.cpp@8c95980d0b66 (annotated)

src/cpu/x86/vm/rdtsc_x86.cpp@8c95980d0b66 (annotated)

src/cpu/x86/vm/rdtsc_x86.cpp

Sat, 07 Nov 2020 10:30:02 +0800

author: aoqi
date: Sat, 07 Nov 2020 10:30:02 +0800
changeset 10026: 8c95980d0b66
parent 9858: b985cbb00e68
permissions: -rw-r--r--

Added tag mips-jdk8u275-b01 for changeset d3b4d62f391f

 /*
  * 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 "os_linux_x86.inline.hpp"
 #ifdef TARGET_OS_ARCH_linux_x86
 # include "os_linux_x86.inline.hpp"
 #endif
 #ifdef TARGET_OS_ARCH_bsd_x86
 # include "os_bsd_x86.inline.hpp"
 #endif
 #ifdef TARGET_OS_ARCH_windows_x86
 # include "os_windows_x86.inline.hpp"
 #endif
 #ifdef TARGET_OS_ARCH_solaris_x86
 # include "os_solaris_x86.inline.hpp"
 #endif
 #include "rdtsc_x86.hpp"
 #include "runtime/thread.inline.hpp"
 #include "vm_version_ext_x86.hpp"
 #include "runtime/os.hpp"
 // The following header contains the implementations of rdtsc()
 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;
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/cpu/x86/vm/rdtsc_x86.cpp@8c95980d0b66 (annotated)

src/cpu/x86/vm/rdtsc_x86.cpp