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 /*

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  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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  * 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.

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 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1MMUTRACKER_HPP

 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1MMUTRACKER_HPP

 #include "memory/allocation.hpp"

 #include "utilities/debug.hpp"

 // Keeps track of the GC work and decides when it is OK to do GC work

 // and for how long so that the MMU invariants are maintained.

 /***** ALL TIMES ARE IN SECS!!!!!!! *****/

 // this is the "interface"

 class G1MMUTracker: public CHeapObj {

 protected:

   double          _time_slice;

   double          _max_gc_time; // this is per time slice

 public:

   G1MMUTracker(double time_slice, double max_gc_time);

   virtual void add_pause(double start, double end, bool gc_thread) = 0;

   virtual double longest_pause(double current_time) = 0;

   virtual double when_sec(double current_time, double pause_time) = 0;

   double max_gc_time() {

     return _max_gc_time;

   }

   inline bool now_max_gc(double current_time) {

     return when_sec(current_time, max_gc_time()) < 0.00001;

   }

   inline double when_max_gc_sec(double current_time) {

     return when_sec(current_time, max_gc_time());

   }

   inline jlong when_max_gc_ms(double current_time) {

     double when = when_max_gc_sec(current_time);

     return (jlong) (when * 1000.0);

   }

   inline jlong when_ms(double current_time, double pause_time) {

     double when = when_sec(current_time, pause_time);

     return (jlong) (when * 1000.0);

   }

 };

 class G1MMUTrackerQueueElem VALUE_OBJ_CLASS_SPEC {

 private:

   double _start_time;

   double _end_time;

 public:

   inline double start_time() { return _start_time; }

   inline double end_time()   { return _end_time; }

   inline double duration()   { return _end_time - _start_time; }

   G1MMUTrackerQueueElem() {

     _start_time = 0.0;

     _end_time   = 0.0;

   }

   G1MMUTrackerQueueElem(double start_time, double end_time) {

     _start_time = start_time;

     _end_time   = end_time;

   }

 };

 // this is an implementation of the MMUTracker using a (fixed-size) queue

 // that keeps track of all the recent pause times

 class G1MMUTrackerQueue: public G1MMUTracker {

 private:

   enum PrivateConstants {

     QueueLength = 64

   };

   // The array keeps track of all the pauses that fall within a time

   // slice (the last time slice during which pauses took place).

   // The data structure implemented is a circular queue.

   // Head "points" to the most recent addition, tail to the oldest one.

   // The array is of fixed size and I don't think we'll need more than

   // two or three entries with the current behaviour of G1 pauses.

   // If the array is full, an easy fix is to look for the pauses with

   // the shortest gap between them and consolidate them.

   // For now, we have taken the expedient alternative of forgetting

   // the oldest entry in the event that +G1UseFixedWindowMMUTracker, thus

   // potentially violating MMU specs for some time thereafter.

   G1MMUTrackerQueueElem _array[QueueLength];

   int                   _head_index;

   int                   _tail_index;

   int                   _no_entries;

   inline int trim_index(int index) {

     return (index + QueueLength) % QueueLength;

   }

   void remove_expired_entries(double current_time);

   double calculate_gc_time(double current_time);

   double longest_pause_internal(double current_time);

   double when_internal(double current_time, double pause_time);

 public:

   G1MMUTrackerQueue(double time_slice, double max_gc_time);

   virtual void add_pause(double start, double end, bool gc_thread);

   virtual double longest_pause(double current_time);

   virtual double when_sec(double current_time, double pause_time);

 };

 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1MMUTRACKER_HPP