1 /*

     2  * Copyright (c) 2001, 2016, 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/g1Policy.hpp"

    29 #include "gc/shared/gcId.hpp"

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

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

    32 #include "gc/shared/gcTraceTime.inline.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             "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,

    98                                                    allocation_context(),

    99                                                    false /* expect_null_cur_alloc_region */);

   100     if (_result != NULL) {

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

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

   103       _pause_succeeded = true;

   104       return;

   105     }

   106   }

   107 

   108   GCCauseSetter x(g1h, _gc_cause);

   109   if (_should_initiate_conc_mark) {

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

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

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

   113     // setting it earlier.

   114     _old_marking_cycles_completed_before = g1h->old_marking_cycles_completed();

   115 

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

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

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

   119 

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

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

   122     // marking cycle is already in progress.

   123     //

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

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

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

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

   128     //

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

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

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

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

   133     // thread checked before calling collect() in

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

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

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

   137     // we do NOT retry the GC.

   138     if (!res) {

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

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

   141         _should_retry_gc = true;

   142       }

   143       return;

   144     }

   145   }

   146 

   147   _pause_succeeded =

   148     g1h->do_collection_pause_at_safepoint(_target_pause_time_ms);

   149   if (_pause_succeeded && _word_size > 0) {

   150     // An allocation had been requested.

   151     _result = g1h->attempt_allocation_at_safepoint(_word_size,

   152                                                    allocation_context(),

   153                                                    true /* expect_null_cur_alloc_region */);

   154   } else {

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

   156     if (!_pause_succeeded) {

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

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

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

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

   161       _should_retry_gc = true;

   162     }

   163   }

   164 }

   165 

   166 void VM_G1IncCollectionPause::doit_epilogue() {

   167   VM_G1OperationWithAllocRequest::doit_epilogue();

   168 

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

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

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

   172   // finish.

   173   if (GCCause::is_user_requested_gc(_gc_cause) &&

   174       _should_initiate_conc_mark) {

   175     assert(ExplicitGCInvokesConcurrent,

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

   177 

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

   179 

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

   181     // in the _old_marking_cycles_completed_before field. We have to

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

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

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

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

   186 

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

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

   189     if (g1h->old_marking_cycles_completed() <=

   190                                           _old_marking_cycles_completed_before) {

   191       // The following is largely copied from CMS

   192 

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

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

   195       JavaThread* jt = (JavaThread*)thr;

   196       ThreadToNativeFromVM native(jt);

   197 

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

   199       while (g1h->old_marking_cycles_completed() <=

   200                                           _old_marking_cycles_completed_before) {

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

   202       }

   203     }

   204   }

   205 }

   206 

   207 void VM_CGC_Operation::doit() {

   208   GCIdMark gc_id_mark(_gc_id);

   209   GCTraceCPUTime tcpu;

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

   211   GCTraceTime(Info, gc) t(_printGCMessage, g1h->concurrent_mark()->gc_timer_cm(), GCCause::_no_gc, true);

   212   IsGCActiveMark x;

   213   _cl->do_void();

   214 }

   215 

   216 bool VM_CGC_Operation::doit_prologue() {

   217   Heap_lock->lock();

   218   return true;

   219 }

   220 

   221 void VM_CGC_Operation::doit_epilogue() {

   222   if (Universe::has_reference_pending_list()) {

   223     Heap_lock->notify_all();

   224   }

   225   Heap_lock->unlock();

   226 }