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

    21  * questions.

    22  *

    23  */

    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 epoch();

    47   static bool  initialize();

    48 };

    49 

    50 #endif // CPU_X86_VM_RDTSC_X86_HPP