1 /*

     2  * Copyright (c) 2001, 2018, 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/g1CollectedHeap.inline.hpp"

    27 #include "gc/g1/g1ConcurrentMarkThread.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.inline.hpp"

    35 

    36 void VM_G1CollectFull::doit() {

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

    38   GCCauseSetter x(g1h, _gc_cause);

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

    40 }

    41 

    42 VM_G1CollectForAllocation::VM_G1CollectForAllocation(size_t         word_size,

    43                                                      uint           gc_count_before,

    44                                                      GCCause::Cause gc_cause,

    45                                                      bool           should_initiate_conc_mark,

    46                                                      double         target_pause_time_ms)

    47   : VM_CollectForAllocation(word_size, gc_count_before, gc_cause),

    48     _pause_succeeded(false),

    49     _should_initiate_conc_mark(should_initiate_conc_mark),

    50     _should_retry_gc(false),

    51     _target_pause_time_ms(target_pause_time_ms),

    52     _old_marking_cycles_completed_before(0) {

    53   guarantee(target_pause_time_ms > 0.0,

    54             "target_pause_time_ms = %1.6lf should be positive",

    55             target_pause_time_ms);

    56   _gc_cause = gc_cause;

    57 }

    58 

    59 bool VM_G1CollectForAllocation::doit_prologue() {

    60   bool res = VM_CollectForAllocation::doit_prologue();

    61   if (!res) {

    62     if (_should_initiate_conc_mark) {

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

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

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

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

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

    68       // until the GC locker is no longer active and then retry the initial mark GC.

    69       _should_retry_gc = true;

    70     }

    71   }

    72   return res;

    73 }

    74 

    75 void VM_G1CollectForAllocation::doit() {

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

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

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

    79 

    80   if (_word_size > 0) {

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

    82     _result = g1h->attempt_allocation_at_safepoint(_word_size,

    83                                                    false /* expect_null_cur_alloc_region */);

    84     if (_result != NULL) {

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

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

    87       _pause_succeeded = true;

    88       return;

    89     }

    90   }

    91 

    92   GCCauseSetter x(g1h, _gc_cause);

    93   if (_should_initiate_conc_mark) {

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

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

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

    97     // setting it earlier.

    98     _old_marking_cycles_completed_before = g1h->old_marking_cycles_completed();

    99 

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

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

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

   103 

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

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

   106     // marking cycle is already in progress.

   107     //

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

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

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

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

   112     //

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

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

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

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

   117     // thread checked before calling collect() in

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

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

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

   121     // we do NOT retry the GC.

   122     if (!res) {

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

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

   125         _should_retry_gc = true;

   126       }

   127       return;

   128     }

   129   }

   130 

   131   // Try a partial collection of some kind.

   132   _pause_succeeded = g1h->do_collection_pause_at_safepoint(_target_pause_time_ms);

   133 

   134   if (_pause_succeeded) {

   135     if (_word_size > 0) {

   136       // An allocation had been requested. Do it, eventually trying a stronger

   137       // kind of GC.

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

   139     } else {

   140       bool should_upgrade_to_full = !g1h->should_do_concurrent_full_gc(_gc_cause) &&

   141                                     !g1h->has_regions_left_for_allocation();

   142       if (should_upgrade_to_full) {

   143         // There has been a request to perform a GC to free some space. We have no

   144         // information on how much memory has been asked for. In case there are

   145         // absolutely no regions left to allocate into, do a maximally compacting full GC.

   146         log_info(gc, ergo)("Attempting maximally compacting collection");

   147         _pause_succeeded = g1h->do_full_collection(false, /* explicit gc */

   148                                                    true   /* clear_all_soft_refs */);

   149       }

   150     }

   151     guarantee(_pause_succeeded, "Elevated collections during the safepoint must always succeed.");

   152   } else {

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

   154     // The only reason for the pause to not be successful is that, the GC locker is

   155     // active (or has become active since the prologue was executed). In this case

   156     // we should retry the pause after waiting for the GC locker to become inactive.

   157     _should_retry_gc = true;

   158   }

   159 }

   160 

   161 void VM_G1CollectForAllocation::doit_epilogue() {

   162   VM_CollectForAllocation::doit_epilogue();

   163 

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

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

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

   167   // finish.

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

   169       _should_initiate_conc_mark) {

   170     assert(ExplicitGCInvokesConcurrent,

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

   172 

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

   174 

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

   176     // in the _old_marking_cycles_completed_before field. We have to

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

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

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

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

   181 

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

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

   184     if (g1h->old_marking_cycles_completed() <=

   185                                           _old_marking_cycles_completed_before) {

   186       // The following is largely copied from CMS

   187 

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

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

   190       JavaThread* jt = (JavaThread*)thr;

   191       ThreadToNativeFromVM native(jt);

   192 

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

   194       while (g1h->old_marking_cycles_completed() <=

   195                                           _old_marking_cycles_completed_before) {

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

   197       }

   198     }

   199   }

   200 }

   201 

   202 void VM_CGC_Operation::doit() {

   203   GCIdMark gc_id_mark(_gc_id);

   204   GCTraceCPUTime tcpu;

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

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

   207   TraceCollectorStats tcs(g1h->g1mm()->conc_collection_counters());

   208   SvcGCMarker sgcm(SvcGCMarker::CONCURRENT);

   209   IsGCActiveMark x;

   210   _cl->do_void();

   211 }

   212 

   213 bool VM_CGC_Operation::doit_prologue() {

   214   Heap_lock->lock();

   215   return true;

   216 }

   217 

   218 void VM_CGC_Operation::doit_epilogue() {

   219   if (Universe::has_reference_pending_list()) {

   220     Heap_lock->notify_all();

   221   }

   222   Heap_lock->unlock();

   223 }