1 /*

     2  * Copyright 2001-2007 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

    20  * CA 95054 USA or visit www.sun.com if you need additional information or

    21  * have any questions.

    22  *

    23  */

    24 

    25 #include "incls/_precompiled.incl"

    26 #include "incls/_concurrentG1RefineThread.cpp.incl"

    27 

    28 // ======= Concurrent Mark Thread ========

    29 

    30 // The CM thread is created when the G1 garbage collector is used

    31 

    32 ConcurrentG1RefineThread::

    33 ConcurrentG1RefineThread(ConcurrentG1Refine* cg1r) :

    34   ConcurrentGCThread(),

    35   _cg1r(cg1r),

    36   _started(false),

    37   _in_progress(false),

    38   _do_traversal(false),

    39   _vtime_accum(0.0),

    40   _co_tracker(G1CRGroup),

    41   _interval_ms(5.0)

    42 {

    43   create_and_start();

    44 }

    45 

    46 const long timeout = 200; // ms.

    47 

    48 void ConcurrentG1RefineThread::traversalBasedRefinement() {

    49   _cg1r->wait_for_ConcurrentG1Refine_enabled();

    50   MutexLocker x(G1ConcRefine_mon);

    51   while (_cg1r->enabled()) {

    52     MutexUnlocker ux(G1ConcRefine_mon);

    53     ResourceMark rm;

    54     HandleMark   hm;

    55 

    56     if (TraceG1Refine) gclog_or_tty->print_cr("G1-Refine starting pass");

    57     _sts.join();

    58     bool no_sleep = _cg1r->refine();

    59     _sts.leave();

    60     if (!no_sleep) {

    61       MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);

    62       // We do this only for the timeout; we don't expect this to be signalled.

    63       CGC_lock->wait(Mutex::_no_safepoint_check_flag, timeout);

    64     }

    65   }

    66 }

    67 

    68 void ConcurrentG1RefineThread::queueBasedRefinement() {

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

    70   // Wait for completed log buffers to exist.

    71   {

    72     MutexLockerEx x(DirtyCardQ_CBL_mon, Mutex::_no_safepoint_check_flag);

    73     while (!_do_traversal && !dcqs.process_completed_buffers() &&

    74            !_should_terminate) {

    75       DirtyCardQ_CBL_mon->wait(Mutex::_no_safepoint_check_flag);

    76     }

    77   }

    78 

    79   if (_should_terminate) {

    80     return;

    81   }

    82 

    83   // Now we take them off (this doesn't hold locks while it applies

    84   // closures.)  (If we did a full collection, then we'll do a full

    85   // traversal.

    86   _sts.join();

    87   if (_do_traversal) {

    88     (void)_cg1r->refine();

    89     switch (_cg1r->get_last_pya()) {

    90     case PYA_cancel: case PYA_continue:

    91       // Continue was caught and handled inside "refine".  If it's still

    92       // "continue" when we get here, we're done.

    93       _do_traversal = false;

    94       break;

    95     case PYA_restart:

    96       assert(_do_traversal, "Because of Full GC.");

    97       break;

    98     }

    99   } else {

   100     int n_logs = 0;

   101     int lower_limit = 0;

   102     double start_vtime_sec; // only used when G1SmoothConcRefine is on

   103     int prev_buffer_num; // only used when G1SmoothConcRefine is on

   104 

   105     if (G1SmoothConcRefine) {

   106       lower_limit = 0;

   107       start_vtime_sec = os::elapsedVTime();

   108       prev_buffer_num = (int) dcqs.completed_buffers_num();

   109     } else {

   110       lower_limit = DCQBarrierProcessCompletedThreshold / 4; // For now.

   111     }

   112     while (dcqs.apply_closure_to_completed_buffer(0, lower_limit)) {

   113       double end_vtime_sec;

   114       double elapsed_vtime_sec;

   115       int elapsed_vtime_ms;

   116       int curr_buffer_num;

   117 

   118       if (G1SmoothConcRefine) {

   119         end_vtime_sec = os::elapsedVTime();

   120         elapsed_vtime_sec = end_vtime_sec - start_vtime_sec;

   121         elapsed_vtime_ms = (int) (elapsed_vtime_sec * 1000.0);

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

   123 

   124         if (curr_buffer_num > prev_buffer_num ||

   125             curr_buffer_num > DCQBarrierProcessCompletedThreshold) {

   126           decreaseInterval(elapsed_vtime_ms);

   127         } else if (curr_buffer_num < prev_buffer_num) {

   128           increaseInterval(elapsed_vtime_ms);

   129         }

   130       }

   131 

   132       sample_young_list_rs_lengths();

   133       _co_tracker.update(false);

   134 

   135       if (G1SmoothConcRefine) {

   136         start_vtime_sec = os::elapsedVTime();

   137         prev_buffer_num = curr_buffer_num;

   138 

   139         _sts.leave();

   140         os::sleep(Thread::current(), (jlong) _interval_ms, false);

   141         _sts.join();

   142       }

   143 

   144       n_logs++;

   145     }

   146     // Make sure we harvest the PYA, if any.

   147     (void)_cg1r->get_pya();

   148   }

   149   _sts.leave();

   150 }

   151 

   152 void ConcurrentG1RefineThread::sample_young_list_rs_lengths() {

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

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

   155   if (g1p->adaptive_young_list_length()) {

   156     int regions_visited = 0;

   157 

   158     g1h->young_list_rs_length_sampling_init();

   159     while (g1h->young_list_rs_length_sampling_more()) {

   160       g1h->young_list_rs_length_sampling_next();

   161       ++regions_visited;

   162 

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

   164       if (regions_visited == 10) {

   165         if (_sts.should_yield()) {

   166           _sts.yield("G1 refine");

   167           // we just abandon the iteration

   168           break;

   169         }

   170         regions_visited = 0;

   171       }

   172     }

   173 

   174     g1p->check_prediction_validity();

   175   }

   176 }

   177 

   178 void ConcurrentG1RefineThread::run() {

   179   initialize_in_thread();

   180   _vtime_start = os::elapsedVTime();

   181   wait_for_universe_init();

   182 

   183   _co_tracker.enable();

   184   _co_tracker.start();

   185 

   186   while (!_should_terminate) {

   187     // wait until started is set.

   188     if (G1RSBarrierUseQueue) {

   189       queueBasedRefinement();

   190     } else {

   191       traversalBasedRefinement();

   192     }

   193     _sts.join();

   194     _co_tracker.update();

   195     _sts.leave();

   196     if (os::supports_vtime()) {

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

   198     } else {

   199       _vtime_accum = 0.0;

   200     }

   201   }

   202   _sts.join();

   203   _co_tracker.update(true);

   204   _sts.leave();

   205   assert(_should_terminate, "just checking");

   206 

   207   terminate();

   208 }

   209 

   210 

   211 void ConcurrentG1RefineThread::yield() {

   212   if (TraceG1Refine) gclog_or_tty->print_cr("G1-Refine-yield");

   213   _sts.yield("G1 refine");

   214   if (TraceG1Refine) gclog_or_tty->print_cr("G1-Refine-yield-end");

   215 }

   216 

   217 void ConcurrentG1RefineThread::stop() {

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

   219   {

   220     MutexLockerEx mu(Terminator_lock);

   221     _should_terminate = true;

   222   }

   223 

   224   {

   225     MutexLockerEx x(DirtyCardQ_CBL_mon, Mutex::_no_safepoint_check_flag);

   226     DirtyCardQ_CBL_mon->notify_all();

   227   }

   228 

   229   {

   230     MutexLockerEx mu(Terminator_lock);

   231     while (!_has_terminated) {

   232       Terminator_lock->wait();

   233     }

   234   }

   235   if (TraceG1Refine) gclog_or_tty->print_cr("G1-Refine-stop");

   236 }

   237 

   238 void ConcurrentG1RefineThread::print() {

   239   gclog_or_tty->print("\"Concurrent G1 Refinement Thread\" ");

   240   Thread::print();

   241   gclog_or_tty->cr();

   242 }

   243 

   244 void ConcurrentG1RefineThread::set_do_traversal(bool b) {

   245   _do_traversal = b;

   246 }