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 "gc/g1/suspendibleThreadSet.hpp"
  31 #include "memory/resourceArea.hpp"
  32 #include "runtime/handles.inline.hpp"
  33 #include "runtime/mutexLocker.hpp"
  34 
  35 ConcurrentG1RefineThread::
  36 ConcurrentG1RefineThread(ConcurrentG1Refine* cg1r, ConcurrentG1RefineThread *next,
  37                          uint worker_id_offset, uint worker_id) :
  38   ConcurrentGCThread(),
  39   _worker_id_offset(worker_id_offset),
  40   _worker_id(worker_id),
  41   _active(false),
  42   _next(next),
  43   _monitor(NULL),
  44   _cg1r(cg1r),
  45   _vtime_accum(0.0)
  46 {
  47 
  48   // Each thread has its own monitor. The i-th thread is responsible for signaling
  49   // to thread i+1 if the number of buffers in the queue exceeds a threshold for this
  50   // thread. Monitors are also used to wake up the threads during termination.
  51   // The 0th worker in notified by mutator threads and has a special monitor.
  52   // The last worker is used for young gen rset size sampling.
  53   if (worker_id > 0) {
  54     _monitor = new Monitor(Mutex::nonleaf, "Refinement monitor", true,
  55                            Monitor::_safepoint_check_never);
  56   } else {
  57     _monitor = DirtyCardQ_CBL_mon;
  58   }
  59   initialize();
  60   create_and_start();
  61 
  62   // set name
  63   set_name("G1 Refine#%d", worker_id);
  64 }
  65 
  66 void ConcurrentG1RefineThread::initialize() {
  67   if (_worker_id < cg1r()->worker_thread_num()) {
  68     // Current thread activation threshold
  69     _threshold = MIN2<int>(cg1r()->thread_threshold_step() * (_worker_id + 1) + cg1r()->green_zone(),
  70                            cg1r()->yellow_zone());
  71     // A thread deactivates once the number of buffer reached a deactivation threshold
  72     _deactivation_threshold = MAX2<int>(_threshold - cg1r()->thread_threshold_step(), cg1r()->green_zone());
  73   } else {
  74     set_active(true);
  75   }
  76 }
  77 
  78 void ConcurrentG1RefineThread::sample_young_list_rs_lengths() {
  79   SuspendibleThreadSetJoiner sts_join;
  80   G1CollectedHeap* g1h = G1CollectedHeap::heap();
  81   G1CollectorPolicy* g1p = g1h->g1_policy();
  82   if (g1p->adaptive_young_list_length()) {
  83     int regions_visited = 0;
  84     g1h->young_list()->rs_length_sampling_init();
  85     while (g1h->young_list()->rs_length_sampling_more()) {
  86       g1h->young_list()->rs_length_sampling_next();
  87       ++regions_visited;
  88 
  89       // we try to yield every time we visit 10 regions
  90       if (regions_visited == 10) {
  91         if (sts_join.should_yield()) {
  92           sts_join.yield();
  93           // we just abandon the iteration
  94           break;
  95         }
  96         regions_visited = 0;
  97       }
  98     }
  99 
 100     g1p->revise_young_list_target_length_if_necessary();
 101   }
 102 }
 103 
 104 void ConcurrentG1RefineThread::run_young_rs_sampling() {
 105   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 106   _vtime_start = os::elapsedVTime();
 107   while(!_should_terminate) {
 108     sample_young_list_rs_lengths();
 109 
 110     if (os::supports_vtime()) {
 111       _vtime_accum = (os::elapsedVTime() - _vtime_start);
 112     } else {
 113       _vtime_accum = 0.0;
 114     }
 115 
 116     MutexLockerEx x(_monitor, Mutex::_no_safepoint_check_flag);
 117     if (_should_terminate) {
 118       break;
 119     }
 120     _monitor->wait(Mutex::_no_safepoint_check_flag, G1ConcRefinementServiceIntervalMillis);
 121   }
 122 }
 123 
 124 void ConcurrentG1RefineThread::wait_for_completed_buffers() {
 125   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 126   MutexLockerEx x(_monitor, Mutex::_no_safepoint_check_flag);
 127   while (!_should_terminate && !is_active()) {
 128     _monitor->wait(Mutex::_no_safepoint_check_flag);
 129   }
 130 }
 131 
 132 bool ConcurrentG1RefineThread::is_active() {
 133   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 134   return _worker_id > 0 ? _active : dcqs.process_completed_buffers();
 135 }
 136 
 137 void ConcurrentG1RefineThread::activate() {
 138   MutexLockerEx x(_monitor, Mutex::_no_safepoint_check_flag);
 139   if (_worker_id > 0) {
 140     if (G1TraceConcRefinement) {
 141       DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 142       gclog_or_tty->print_cr("G1-Refine-activated worker %d, on threshold %d, current %d",
 143                              _worker_id, _threshold, (int)dcqs.completed_buffers_num());
 144     }
 145     set_active(true);
 146   } else {
 147     DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 148     dcqs.set_process_completed(true);
 149   }
 150   _monitor->notify();
 151 }
 152 
 153 void ConcurrentG1RefineThread::deactivate() {
 154   MutexLockerEx x(_monitor, Mutex::_no_safepoint_check_flag);
 155   if (_worker_id > 0) {
 156     if (G1TraceConcRefinement) {
 157       DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 158       gclog_or_tty->print_cr("G1-Refine-deactivated worker %d, off threshold %d, current %d",
 159                              _worker_id, _deactivation_threshold, (int)dcqs.completed_buffers_num());
 160     }
 161     set_active(false);
 162   } else {
 163     DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 164     dcqs.set_process_completed(false);
 165   }
 166 }
 167 
 168 void ConcurrentG1RefineThread::run() {
 169   initialize_in_thread();
 170   wait_for_universe_init();
 171 
 172   if (_worker_id >= cg1r()->worker_thread_num()) {
 173     run_young_rs_sampling();
 174     terminate();
 175     return;
 176   }
 177 
 178   _vtime_start = os::elapsedVTime();
 179   while (!_should_terminate) {
 180     DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 181 
 182     // Wait for work
 183     wait_for_completed_buffers();
 184 
 185     if (_should_terminate) {
 186       break;
 187     }
 188 
 189     {
 190       SuspendibleThreadSetJoiner sts_join;
 191       BufferedRefineCardTableEntryClosure cl;
 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           cl.flush_buffer();
 206           deactivate();
 207           break;
 208         }
 209 
 210         // Check if we need to activate the next thread.
 211         if (_next != NULL && !_next->is_active() && curr_buffer_num > _next->_threshold) {
 212           _next->activate();
 213         }
 214       } while (dcqs.apply_closure_to_completed_buffer(&cl, _worker_id + _worker_id_offset, cg1r()->green_zone()));
 215 
 216       cl.flush_buffer();
 217 
 218       // We can exit the loop above while being active if there was a yield request.
 219       if (is_active()) {
 220         deactivate();
 221       }
 222     }
 223 
 224     if (os::supports_vtime()) {
 225       _vtime_accum = (os::elapsedVTime() - _vtime_start);
 226     } else {
 227       _vtime_accum = 0.0;
 228     }
 229   }
 230   assert(_should_terminate, "just checking");
 231   terminate();
 232 }
 233 
 234 void ConcurrentG1RefineThread::stop() {
 235   // it is ok to take late safepoints here, if needed
 236   {
 237     MutexLockerEx mu(Terminator_lock);
 238     _should_terminate = true;
 239   }
 240 
 241   {
 242     MutexLockerEx x(_monitor, Mutex::_no_safepoint_check_flag);
 243     _monitor->notify();
 244   }
 245 
 246   {
 247     MutexLockerEx mu(Terminator_lock);
 248     while (!_has_terminated) {
 249       Terminator_lock->wait();
 250     }
 251   }
 252   if (G1TraceConcRefinement) {
 253     gclog_or_tty->print_cr("G1-Refine-stop");
 254   }
 255 }