1 /*

     2  * Copyright (c) 2001, 2015, 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 #include "precompiled.hpp"

    26 #include "gc/g1/concurrentG1Refine.hpp"

    27 #include "gc/g1/concurrentG1RefineThread.hpp"

    28 #include "gc/g1/g1CollectedHeap.inline.hpp"

    29 #include "gc/g1/g1CollectorPolicy.hpp"

    30 #include "memory/resourceArea.hpp"

    31 #include "runtime/handles.inline.hpp"

    32 #include "runtime/mutexLocker.hpp"

    33 

    34 ConcurrentG1RefineThread::

    35 ConcurrentG1RefineThread(ConcurrentG1Refine* cg1r, ConcurrentG1RefineThread *next,

    36                          CardTableEntryClosure* refine_closure,

    37                          uint worker_id_offset, uint worker_id) :

    38   ConcurrentGCThread(),

    39   _refine_closure(refine_closure),

    40   _worker_id_offset(worker_id_offset),

    41   _worker_id(worker_id),

    42   _active(false),

    43   _next(next),

    44   _monitor(NULL),

    45   _cg1r(cg1r),

    46   _vtime_accum(0.0)

    47 {

    48 

    49   // Each thread has its own monitor. The i-th thread is responsible for signaling

    50   // to thread i+1 if the number of buffers in the queue exceeds a threshold for this

    51   // thread. Monitors are also used to wake up the threads during termination.

    52   // The 0th worker in notified by mutator threads and has a special monitor.

    53   // The last worker is used for young gen rset size sampling.

    54   if (worker_id > 0) {

    55     _monitor = new Monitor(Mutex::nonleaf, "Refinement monitor", true,

    56                            Monitor::_safepoint_check_never);

    57   } else {

    58     _monitor = DirtyCardQ_CBL_mon;

    59   }

    60   initialize();

    61   create_and_start();

    62 

    63   // set name

    64   set_name("G1 Refine#%d", worker_id);

    65 }

    66 

    67 void ConcurrentG1RefineThread::initialize() {

    68   if (_worker_id < cg1r()->worker_thread_num()) {

    69     // Current thread activation threshold

    70     _threshold = MIN2<int>(cg1r()->thread_threshold_step() * (_worker_id + 1) + cg1r()->green_zone(),

    71                            cg1r()->yellow_zone());

    72     // A thread deactivates once the number of buffer reached a deactivation threshold

    73     _deactivation_threshold = MAX2<int>(_threshold - cg1r()->thread_threshold_step(), cg1r()->green_zone());

    74   } else {

    75     set_active(true);

    76   }

    77 }

    78 

    79 void ConcurrentG1RefineThread::sample_young_list_rs_lengths() {

    80   SuspendibleThreadSetJoiner sts_join;

    81   G1CollectedHeap* g1h = G1CollectedHeap::heap();

    82   G1CollectorPolicy* g1p = g1h->g1_policy();

    83   if (g1p->adaptive_young_list_length()) {

    84     int regions_visited = 0;

    85     g1h->young_list()->rs_length_sampling_init();

    86     while (g1h->young_list()->rs_length_sampling_more()) {

    87       g1h->young_list()->rs_length_sampling_next();

    88       ++regions_visited;

    89 

    90       // we try to yield every time we visit 10 regions

    91       if (regions_visited == 10) {

    92         if (sts_join.should_yield()) {

    93           sts_join.yield();

    94           // we just abandon the iteration

    95           break;

    96         }

    97         regions_visited = 0;

    98       }

    99     }

   100 

   101     g1p->revise_young_list_target_length_if_necessary();

   102   }

   103 }

   104 

   105 void ConcurrentG1RefineThread::run_young_rs_sampling() {

   106   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();

   107   _vtime_start = os::elapsedVTime();

   108   while(!_should_terminate) {

   109     sample_young_list_rs_lengths();

   110 

   111     if (os::supports_vtime()) {

   112       _vtime_accum = (os::elapsedVTime() - _vtime_start);

   113     } else {

   114       _vtime_accum = 0.0;

   115     }

   116 

   117     MutexLockerEx x(_monitor, Mutex::_no_safepoint_check_flag);

   118     if (_should_terminate) {

   119       break;

   120     }

   121     _monitor->wait(Mutex::_no_safepoint_check_flag, G1ConcRefinementServiceIntervalMillis);

   122   }

   123 }

   124 

   125 void ConcurrentG1RefineThread::wait_for_completed_buffers() {

   126   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();

   127   MutexLockerEx x(_monitor, Mutex::_no_safepoint_check_flag);

   128   while (!_should_terminate && !is_active()) {

   129     _monitor->wait(Mutex::_no_safepoint_check_flag);

   130   }

   131 }

   132 

   133 bool ConcurrentG1RefineThread::is_active() {

   134   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();

   135   return _worker_id > 0 ? _active : dcqs.process_completed_buffers();

   136 }

   137 

   138 void ConcurrentG1RefineThread::activate() {

   139   MutexLockerEx x(_monitor, Mutex::_no_safepoint_check_flag);

   140   if (_worker_id > 0) {

   141     if (G1TraceConcRefinement) {

   142       DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();

   143       gclog_or_tty->print_cr("G1-Refine-activated worker %d, on threshold %d, current %d",

   144                              _worker_id, _threshold, (int)dcqs.completed_buffers_num());

   145     }

   146     set_active(true);

   147   } else {

   148     DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();

   149     dcqs.set_process_completed(true);

   150   }

   151   _monitor->notify();

   152 }

   153 

   154 void ConcurrentG1RefineThread::deactivate() {

   155   MutexLockerEx x(_monitor, Mutex::_no_safepoint_check_flag);

   156   if (_worker_id > 0) {

   157     if (G1TraceConcRefinement) {

   158       DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();

   159       gclog_or_tty->print_cr("G1-Refine-deactivated worker %d, off threshold %d, current %d",

   160                              _worker_id, _deactivation_threshold, (int)dcqs.completed_buffers_num());

   161     }

   162     set_active(false);

   163   } else {

   164     DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();

   165     dcqs.set_process_completed(false);

   166   }

   167 }

   168 

   169 void ConcurrentG1RefineThread::run() {

   170   initialize_in_thread();

   171   wait_for_universe_init();

   172 

   173   if (_worker_id >= cg1r()->worker_thread_num()) {

   174     run_young_rs_sampling();

   175     terminate();

   176     return;

   177   }

   178 

   179   _vtime_start = os::elapsedVTime();

   180   while (!_should_terminate) {

   181     DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();

   182 

   183     // Wait for work

   184     wait_for_completed_buffers();

   185 

   186     if (_should_terminate) {

   187       break;

   188     }

   189 

   190     {

   191       SuspendibleThreadSetJoiner sts_join;

   192 

   193       do {

   194         int curr_buffer_num = (int)dcqs.completed_buffers_num();

   195         // If the number of the buffers falls down into the yellow zone,

   196         // that means that the transition period after the evacuation pause has ended.

   197         if (dcqs.completed_queue_padding() > 0 && curr_buffer_num <= cg1r()->yellow_zone()) {

   198           dcqs.set_completed_queue_padding(0);

   199         }

   200 

   201         if (_worker_id > 0 && curr_buffer_num <= _deactivation_threshold) {

   202           // If the number of the buffer has fallen below our threshold

   203           // we should deactivate. The predecessor will reactivate this

   204           // thread should the number of the buffers cross the threshold again.

   205           deactivate();

   206           break;

   207         }

   208 

   209         // Check if we need to activate the next thread.

   210         if (_next != NULL && !_next->is_active() && curr_buffer_num > _next->_threshold) {

   211           _next->activate();

   212         }

   213       } while (dcqs.apply_closure_to_completed_buffer(_refine_closure, _worker_id + _worker_id_offset, cg1r()->green_zone()));

   214 

   215       // We can exit the loop above while being active if there was a yield request.

   216       if (is_active()) {

   217         deactivate();

   218       }

   219     }

   220 

   221     if (os::supports_vtime()) {

   222       _vtime_accum = (os::elapsedVTime() - _vtime_start);

   223     } else {

   224       _vtime_accum = 0.0;

   225     }

   226   }

   227   assert(_should_terminate, "just checking");

   228   terminate();

   229 }

   230 

   231 void ConcurrentG1RefineThread::stop() {

   232   // it is ok to take late safepoints here, if needed

   233   {

   234     MutexLockerEx mu(Terminator_lock);

   235     _should_terminate = true;

   236   }

   237 

   238   {

   239     MutexLockerEx x(_monitor, Mutex::_no_safepoint_check_flag);

   240     _monitor->notify();

   241   }

   242 

   243   {

   244     MutexLockerEx mu(Terminator_lock);

   245     while (!_has_terminated) {

   246       Terminator_lock->wait();

   247     }

   248   }

   249   if (G1TraceConcRefinement) {

   250     gclog_or_tty->print_cr("G1-Refine-stop");

   251   }

   252 }

   253