1 /*
   2  * Copyright (c) 2012, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
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  24 
  25 #ifndef CPU_X86_VM_RDTSC_X86_HPP
  26 #define CPU_X86_VM_RDTSC_X86_HPP
  27 
  28 #include "memory/allocation.hpp"
  29 #include "utilities/macros.hpp"
  30 
  31 // Interface to the x86 rdtsc() time counter, if available.
  32 // Not guaranteed to be synchronized across hardware threads and
  33 // therefore software threads, and can be updated asynchronously
  34 // by software. elapsed_counter() can jump backwards
  35 // as well as jump forward when threads query different cores/sockets.
  36 // Very much not recommended for general use.
  37 // INVTSC is a minimal requirement for auto-enablement.
  38 
  39 class Rdtsc : AllStatic {
  40  public:
  41   static jlong elapsed_counter(); // provides quick time stamps
  42   static jlong frequency();       // tsc register
  43   static bool  is_supported();    // InvariantTSC
  44   static jlong raw();             // direct rdtsc() access
  45   static bool  is_elapsed_counter_enabled(); // turn off with -XX:-UseFastUnorderedTimeStamps
  46   static jlong elapsed_counter_baseline();
  47   static bool  initialize();
  48 };
  49 
  50 #endif // CPU_X86_VM_RDTSC_X86_HPP