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/concurrentMarkThread.inline.hpp"

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

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

    29 #include "gc/g1/g1Log.hpp"

    30 #include "gc/g1/vm_operations_g1.hpp"

    31 #include "gc/shared/gcTimer.hpp"

    32 #include "gc/shared/gcTraceTime.hpp"

    33 #include "gc/shared/isGCActiveMark.hpp"

    34 #include "runtime/interfaceSupport.hpp"

    35 

    36 VM_G1CollectForAllocation::VM_G1CollectForAllocation(uint gc_count_before,

    37                                                      size_t word_size)

    38   : VM_G1OperationWithAllocRequest(gc_count_before, word_size,

    39                                    GCCause::_allocation_failure) {

    40   guarantee(word_size != 0, "An allocation should always be requested with this operation.");

    41 }

    42 

    43 void VM_G1CollectForAllocation::doit() {

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

    45   GCCauseSetter x(g1h, _gc_cause);

    46 

    47   _result = g1h->satisfy_failed_allocation(_word_size, allocation_context(), &_pause_succeeded);

    48   assert(_result == NULL || _pause_succeeded,

    49          "if we get back a result, the pause should have succeeded");

    50 }

    51 

    52 void VM_G1CollectFull::doit() {

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

    54   GCCauseSetter x(g1h, _gc_cause);

    55   g1h->do_full_collection(false /* clear_all_soft_refs */);

    56 }

    57 

    58 VM_G1IncCollectionPause::VM_G1IncCollectionPause(uint           gc_count_before,

    59                                                  size_t         word_size,

    60                                                  bool           should_initiate_conc_mark,

    61                                                  double         target_pause_time_ms,

    62                                                  GCCause::Cause gc_cause)

    63   : VM_G1OperationWithAllocRequest(gc_count_before, word_size, gc_cause),

    64     _should_initiate_conc_mark(should_initiate_conc_mark),

    65     _target_pause_time_ms(target_pause_time_ms),

    66     _should_retry_gc(false),

    67     _old_marking_cycles_completed_before(0) {

    68   guarantee(target_pause_time_ms > 0.0,

    69             err_msg("target_pause_time_ms = %1.6lf should be positive",

    70                     target_pause_time_ms));

    71   _gc_cause = gc_cause;

    72 }

    73 

    74 bool VM_G1IncCollectionPause::doit_prologue() {

    75   bool res = VM_G1OperationWithAllocRequest::doit_prologue();

    76   if (!res) {

    77     if (_should_initiate_conc_mark) {

    78       // The prologue can fail for a couple of reasons. The first is that another GC

    79       // got scheduled and prevented the scheduling of the initial mark GC. The

    80       // second is that the GC locker may be active and the heap can't be expanded.

    81       // In both cases we want to retry the GC so that the initial mark pause is

    82       // actually scheduled. In the second case, however, we should stall until

    83       // until the GC locker is no longer active and then retry the initial mark GC.

    84       _should_retry_gc = true;

    85     }

    86   }

    87   return res;

    88 }

    89 

    90 void VM_G1IncCollectionPause::doit() {

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

    92   assert(!_should_initiate_conc_mark || g1h->should_do_concurrent_full_gc(_gc_cause),

    93       "only a GC locker, a System.gc(), stats update, whitebox, or a hum allocation induced GC should start a cycle");

    94 

    95   if (_word_size > 0) {

    96     // An allocation has been requested. So, try to do that first.

    97     _result = g1h->attempt_allocation_at_safepoint(_word_size, allocation_context(),

    98                                      false /* expect_null_cur_alloc_region */);

    99     if (_result != NULL) {

   100       // If we can successfully allocate before we actually do the

   101       // pause then we will consider this pause successful.

   102       _pause_succeeded = true;

   103       return;

   104     }

   105   }

   106 

   107   GCCauseSetter x(g1h, _gc_cause);

   108   if (_should_initiate_conc_mark) {

   109     // It's safer to read old_marking_cycles_completed() here, given

   110     // that noone else will be updating it concurrently. Since we'll

   111     // only need it if we're initiating a marking cycle, no point in

   112     // setting it earlier.

   113     _old_marking_cycles_completed_before = g1h->old_marking_cycles_completed();

   114 

   115     // At this point we are supposed to start a concurrent cycle. We

   116     // will do so if one is not already in progress.

   117     bool res = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause);

   118 

   119     // The above routine returns true if we were able to force the

   120     // next GC pause to be an initial mark; it returns false if a

   121     // marking cycle is already in progress.

   122     //

   123     // If a marking cycle is already in progress just return and skip the

   124     // pause below - if the reason for requesting this initial mark pause

   125     // was due to a System.gc() then the requesting thread should block in

   126     // doit_epilogue() until the marking cycle is complete.

   127     //

   128     // If this initial mark pause was requested as part of a humongous

   129     // allocation then we know that the marking cycle must just have

   130     // been started by another thread (possibly also allocating a humongous

   131     // object) as there was no active marking cycle when the requesting

   132     // thread checked before calling collect() in

   133     // attempt_allocation_humongous(). Retrying the GC, in this case,

   134     // will cause the requesting thread to spin inside collect() until the

   135     // just started marking cycle is complete - which may be a while. So

   136     // we do NOT retry the GC.

   137     if (!res) {

   138       assert(_word_size == 0, "Concurrent Full GC/Humongous Object IM shouldn't be allocating");

   139       if (_gc_cause != GCCause::_g1_humongous_allocation) {

   140         _should_retry_gc = true;

   141       }

   142       return;

   143     }

   144   }

   145 

   146   _pause_succeeded =

   147     g1h->do_collection_pause_at_safepoint(_target_pause_time_ms);

   148   if (_pause_succeeded && _word_size > 0) {

   149     // An allocation had been requested.

   150     _result = g1h->attempt_allocation_at_safepoint(_word_size, allocation_context(),

   151                                       true /* expect_null_cur_alloc_region */);

   152   } else {

   153     assert(_result == NULL, "invariant");

   154     if (!_pause_succeeded) {

   155       // Another possible reason reason for the pause to not be successful

   156       // is that, again, the GC locker is active (and has become active

   157       // since the prologue was executed). In this case we should retry

   158       // the pause after waiting for the GC locker to become inactive.

   159       _should_retry_gc = true;

   160     }

   161   }

   162 }

   163 

   164 void VM_G1IncCollectionPause::doit_epilogue() {

   165   VM_G1OperationWithAllocRequest::doit_epilogue();

   166 

   167   // If the pause was initiated by a System.gc() and

   168   // +ExplicitGCInvokesConcurrent, we have to wait here for the cycle

   169   // that just started (or maybe one that was already in progress) to

   170   // finish.

   171   if (_gc_cause == GCCause::_java_lang_system_gc &&

   172       _should_initiate_conc_mark) {

   173     assert(ExplicitGCInvokesConcurrent,

   174            "the only way to be here is if ExplicitGCInvokesConcurrent is set");

   175 

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

   177 

   178     // In the doit() method we saved g1h->old_marking_cycles_completed()

   179     // in the _old_marking_cycles_completed_before field. We have to

   180     // wait until we observe that g1h->old_marking_cycles_completed()

   181     // has increased by at least one. This can happen if a) we started

   182     // a cycle and it completes, b) a cycle already in progress

   183     // completes, or c) a Full GC happens.

   184 

   185     // If the condition has already been reached, there's no point in

   186     // actually taking the lock and doing the wait.

   187     if (g1h->old_marking_cycles_completed() <=

   188                                           _old_marking_cycles_completed_before) {

   189       // The following is largely copied from CMS

   190 

   191       Thread* thr = Thread::current();

   192       assert(thr->is_Java_thread(), "invariant");

   193       JavaThread* jt = (JavaThread*)thr;

   194       ThreadToNativeFromVM native(jt);

   195 

   196       MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);

   197       while (g1h->old_marking_cycles_completed() <=

   198                                           _old_marking_cycles_completed_before) {

   199         FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);

   200       }

   201     }

   202   }

   203 }

   204 

   205 void VM_CGC_Operation::acquire_pending_list_lock() {

   206   assert(_needs_pll, "don't call this otherwise");

   207   // The caller may block while communicating

   208   // with the SLT thread in order to acquire/release the PLL.

   209   SurrogateLockerThread* slt = ConcurrentMarkThread::slt();

   210   if (slt != NULL) {

   211     slt->manipulatePLL(SurrogateLockerThread::acquirePLL);

   212   } else {

   213     SurrogateLockerThread::report_missing_slt();

   214   }

   215 }

   216 

   217 void VM_CGC_Operation::release_and_notify_pending_list_lock() {

   218   assert(_needs_pll, "don't call this otherwise");

   219   // The caller may block while communicating

   220   // with the SLT thread in order to acquire/release the PLL.

   221   ConcurrentMarkThread::slt()->

   222     manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL);

   223 }

   224 

   225 void VM_CGC_Operation::doit() {

   226   TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);

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

   228   GCTraceTime t(_printGCMessage, G1Log::fine(), true, g1h->gc_timer_cm(), g1h->concurrent_mark()->concurrent_gc_id());

   229   IsGCActiveMark x;

   230   _cl->do_void();

   231 }

   232 

   233 bool VM_CGC_Operation::doit_prologue() {

   234   // Note the relative order of the locks must match that in

   235   // VM_GC_Operation::doit_prologue() or deadlocks can occur

   236   if (_needs_pll) {

   237     acquire_pending_list_lock();

   238   }

   239 

   240   Heap_lock->lock();

   241   return true;

   242 }

   243 

   244 void VM_CGC_Operation::doit_epilogue() {

   245   // Note the relative order of the unlocks must match that in

   246   // VM_GC_Operation::doit_epilogue()

   247   Heap_lock->unlock();

   248   if (_needs_pll) {

   249     release_and_notify_pending_list_lock();

   250   }

   251 }