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 /*

  * Copyright (c) 2001, 2011, 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 "gc_implementation/g1/g1MMUTracker.hpp"

 #include "runtime/mutexLocker.hpp"

 #include "utilities/ostream.hpp"

 #define _DISABLE_MMU                             0

 // can't rely on comparing doubles with tolerating a small margin for error

 #define SMALL_MARGIN 0.0000001

 #define is_double_leq_0(_value) ( (_value) < SMALL_MARGIN )

 #define is_double_leq(_val1, _val2) is_double_leq_0((_val1) - (_val2))

 #define is_double_geq(_val1, _val2) is_double_leq_0((_val2) - (_val1))

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

 G1MMUTracker::G1MMUTracker(double time_slice, double max_gc_time) :

   _time_slice(time_slice),

   _max_gc_time(max_gc_time) { }

 G1MMUTrackerQueue::G1MMUTrackerQueue(double time_slice, double max_gc_time) :

   G1MMUTracker(time_slice, max_gc_time),

   _head_index(0),

   _tail_index(trim_index(_head_index+1)),

   _no_entries(0) { }

 void G1MMUTrackerQueue::remove_expired_entries(double current_time) {

   double limit = current_time - _time_slice;

   while (_no_entries > 0) {

     if (is_double_geq(limit, _array[_tail_index].end_time())) {

       _tail_index = trim_index(_tail_index + 1);

       --_no_entries;

     } else

       return;

   }

   guarantee(_no_entries == 0, "should have no entries in the array");

 }

 double G1MMUTrackerQueue::calculate_gc_time(double current_time) {

   double gc_time = 0.0;

   double limit = current_time - _time_slice;

   for (int i = 0; i < _no_entries; ++i) {

     int index = trim_index(_tail_index + i);

     G1MMUTrackerQueueElem *elem = &_array[index];

     if (elem->end_time() > limit) {

       if (elem->start_time() > limit)

         gc_time += elem->duration();

       else

         gc_time += elem->end_time() - limit;

     }

   }

   return gc_time;

 }

 void G1MMUTrackerQueue::add_pause(double start, double end, bool gc_thread) {

   double longest_allowed = longest_pause_internal(start);

   if (longest_allowed < 0.0)

     longest_allowed = 0.0;

   double duration = end - start;

   remove_expired_entries(end);

   if (_no_entries == QueueLength) {

     // OK, we've filled up the queue. There are a few ways

     // of dealing with this "gracefully"

     //   increase the array size (:-)

     //   remove the oldest entry (this might allow more GC time for

     //     the time slice than what's allowed) - this is what we

     //     currently do

     //   consolidate the two entries with the minimum gap between them

     //     (this might allow less GC time than what's allowed)

     // In the case where ScavengeALot is true, such overflow is not

     // uncommon; in such cases, we can, without much loss of precision

     // or performance (we are GC'ing most of the time anyway!),

     // simply overwrite the oldest entry in the tracker.

     _head_index = trim_index(_head_index + 1);

     assert(_head_index == _tail_index, "Because we have a full circular buffer");

     _tail_index = trim_index(_tail_index + 1);

   } else {

     _head_index = trim_index(_head_index + 1);

     ++_no_entries;

   }

   _array[_head_index] = G1MMUTrackerQueueElem(start, end);

 }

 // basically the _internal call does not remove expired entries

 // this is for trying things out in the future and a couple

 // of other places (debugging)

 double G1MMUTrackerQueue::longest_pause(double current_time) {

   if (_DISABLE_MMU)

     return _max_gc_time;

   MutexLockerEx x(MMUTracker_lock, Mutex::_no_safepoint_check_flag);

   remove_expired_entries(current_time);

   return longest_pause_internal(current_time);

 }

 double G1MMUTrackerQueue::longest_pause_internal(double current_time) {

   double target_time = _max_gc_time;

   while( 1 ) {

     double gc_time =

       calculate_gc_time(current_time + target_time);

     double diff = target_time + gc_time - _max_gc_time;

     if (!is_double_leq_0(diff)) {

       target_time -= diff;

       if (is_double_leq_0(target_time)) {

         target_time = -1.0;

         break;

       }

     } else {

       break;

     }

   }

   return target_time;

 }

 // basically the _internal call does not remove expired entries

 // this is for trying things out in the future and a couple

 // of other places (debugging)

 double G1MMUTrackerQueue::when_sec(double current_time, double pause_time) {

   if (_DISABLE_MMU)

     return 0.0;

   MutexLockerEx x(MMUTracker_lock, Mutex::_no_safepoint_check_flag);

   remove_expired_entries(current_time);

   return when_internal(current_time, pause_time);

 }

 double G1MMUTrackerQueue::when_internal(double current_time,

                                         double pause_time) {

   // if the pause is over the maximum, just assume that it's the maximum

   double adjusted_pause_time =

     (pause_time > max_gc_time()) ? max_gc_time() : pause_time;

   double earliest_end = current_time + adjusted_pause_time;

   double limit = earliest_end - _time_slice;

   double gc_time = calculate_gc_time(earliest_end);

   double diff = gc_time + adjusted_pause_time - max_gc_time();

   if (is_double_leq_0(diff))

     return 0.0;

   int index = _tail_index;

   while ( 1 ) {

     G1MMUTrackerQueueElem *elem = &_array[index];

     if (elem->end_time() > limit) {

       if (elem->start_time() > limit)

         diff -= elem->duration();

       else

         diff -= elem->end_time() - limit;

       if (is_double_leq_0(diff))

         return  elem->end_time() + diff + _time_slice - adjusted_pause_time - current_time;

     }

     index = trim_index(index+1);

     guarantee(index != trim_index(_head_index + 1), "should not go past head");

   }

 }