1 /*
   2  * Copyright (c) 2005, 2020, 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 "classfile/classLoader.hpp"
  27 #include "classfile/javaClasses.hpp"
  28 #include "gc/shared/allocTracer.hpp"
  29 #include "gc/shared/gcId.hpp"
  30 #include "gc/shared/gcLocker.hpp"
  31 #include "gc/shared/gcVMOperations.hpp"
  32 #include "gc/shared/genCollectedHeap.hpp"
  33 #include "interpreter/oopMapCache.hpp"
  34 #include "logging/log.hpp"
  35 #include "memory/oopFactory.hpp"
  36 #include "memory/universe.hpp"
  37 #include "runtime/handles.inline.hpp"
  38 #include "runtime/init.hpp"
  39 #include "utilities/dtrace.hpp"
  40 #include "utilities/macros.hpp"
  41 #include "utilities/preserveException.hpp"
  42 #if INCLUDE_G1GC
  43 #include "gc/g1/g1CollectedHeap.inline.hpp"
  44 #include "gc/g1/g1Policy.hpp"
  45 #endif // INCLUDE_G1GC
  46 
  47 VM_GC_Operation::~VM_GC_Operation() {
  48   CollectedHeap* ch = Universe::heap();
  49   ch->soft_ref_policy()->set_all_soft_refs_clear(false);
  50 }
  51 
  52 // The same dtrace probe can't be inserted in two different files, so we
  53 // have to call it here, so it's only in one file.  Can't create new probes
  54 // for the other file anymore.   The dtrace probes have to remain stable.
  55 void VM_GC_Operation::notify_gc_begin(bool full) {
  56   HOTSPOT_GC_BEGIN(
  57                    full);
  58 }
  59 
  60 void VM_GC_Operation::notify_gc_end() {
  61   HOTSPOT_GC_END();
  62 }
  63 
  64 // Allocations may fail in several threads at about the same time,
  65 // resulting in multiple gc requests.  We only want to do one of them.
  66 // In case a GC locker is active and the need for a GC is already signaled,
  67 // we want to skip this GC attempt altogether, without doing a futile
  68 // safepoint operation.
  69 bool VM_GC_Operation::skip_operation() const {
  70   bool skip = (_gc_count_before != Universe::heap()->total_collections());
  71   if (_full && skip) {
  72     skip = (_full_gc_count_before != Universe::heap()->total_full_collections());
  73   }
  74   if (!skip && GCLocker::is_active_and_needs_gc()) {
  75     skip = Universe::heap()->is_maximal_no_gc();
  76     assert(!(skip && (_gc_cause == GCCause::_gc_locker)),
  77            "GCLocker cannot be active when initiating GC");
  78   }
  79   return skip;
  80 }
  81 
  82 bool VM_GC_Operation::doit_prologue() {
  83   assert(((_gc_cause != GCCause::_no_gc) &&
  84           (_gc_cause != GCCause::_no_cause_specified)), "Illegal GCCause");
  85 
  86   // To be able to handle a GC the VM initialization needs to be completed.
  87   if (!is_init_completed()) {
  88     vm_exit_during_initialization(
  89       err_msg("GC triggered before VM initialization completed. Try increasing "
  90               "NewSize, current value " SIZE_FORMAT "%s.",
  91               byte_size_in_proper_unit(NewSize),
  92               proper_unit_for_byte_size(NewSize)));
  93   }
  94 
  95   // If the GC count has changed someone beat us to the collection
  96   Heap_lock->lock();
  97 
  98   // Check invocations
  99   if (skip_operation()) {
 100     // skip collection
 101     Heap_lock->unlock();
 102     _prologue_succeeded = false;
 103   } else {
 104     _prologue_succeeded = true;
 105   }
 106   return _prologue_succeeded;
 107 }
 108 
 109 
 110 void VM_GC_Operation::doit_epilogue() {
 111   // Clean up old interpreter OopMap entries that were replaced
 112   // during the GC thread root traversal.
 113   OopMapCache::cleanup_old_entries();
 114   if (Universe::has_reference_pending_list()) {
 115     Heap_lock->notify_all();
 116   }
 117   Heap_lock->unlock();
 118 }
 119 
 120 bool VM_GC_HeapInspection::skip_operation() const {
 121   return false;
 122 }
 123 
 124 bool VM_GC_HeapInspection::collect() {
 125   if (GCLocker::is_active()) {
 126     return false;
 127   }
 128   Universe::heap()->collect_as_vm_thread(GCCause::_heap_inspection);
 129   return true;
 130 }
 131 
 132 void VM_GC_HeapInspection::doit() {
 133   Universe::heap()->ensure_parsability(false); // must happen, even if collection does
 134                                                // not happen (e.g. due to GCLocker)
 135                                                // or _full_gc being false
 136   if (_full_gc) {
 137     if (!collect()) {
 138       // The collection attempt was skipped because the gc locker is held.
 139       // The following dump may then be a tad misleading to someone expecting
 140       // only live objects to show up in the dump (see CR 6944195). Just issue
 141       // a suitable warning in that case and do not attempt to do a collection.
 142       // The latter is a subtle point, because even a failed attempt
 143       // to GC will, in fact, induce one in the future, which we
 144       // probably want to avoid in this case because the GC that we may
 145       // be about to attempt holds value for us only
 146       // if it happens now and not if it happens in the eventual
 147       // future.
 148       log_warning(gc)("GC locker is held; pre-dump GC was skipped");
 149     }
 150   }
 151   HeapInspection inspect;
 152   inspect.heap_inspection(_out);
 153 }
 154 
 155 
 156 void VM_GenCollectForAllocation::doit() {
 157   SvcGCMarker sgcm(SvcGCMarker::MINOR);
 158 
 159   GenCollectedHeap* gch = GenCollectedHeap::heap();
 160   GCCauseSetter gccs(gch, _gc_cause);
 161   _result = gch->satisfy_failed_allocation(_word_size, _tlab);
 162   assert(_result == NULL || gch->is_in_reserved(_result), "result not in heap");
 163 
 164   if (_result == NULL && GCLocker::is_active_and_needs_gc()) {
 165     set_gc_locked();
 166   }
 167 }
 168 
 169 void VM_GenCollectFull::doit() {
 170   SvcGCMarker sgcm(SvcGCMarker::FULL);
 171 
 172   GenCollectedHeap* gch = GenCollectedHeap::heap();
 173   GCCauseSetter gccs(gch, _gc_cause);
 174   gch->do_full_collection(gch->must_clear_all_soft_refs(), _max_generation);
 175 }
 176 
 177 VM_CollectForMetadataAllocation::VM_CollectForMetadataAllocation(ClassLoaderData* loader_data,
 178                                                                  size_t size,
 179                                                                  Metaspace::MetadataType mdtype,
 180                                                                  uint gc_count_before,
 181                                                                  uint full_gc_count_before,
 182                                                                  GCCause::Cause gc_cause)
 183     : VM_GC_Operation(gc_count_before, gc_cause, full_gc_count_before, true),
 184       _result(NULL), _size(size), _mdtype(mdtype), _loader_data(loader_data) {
 185   assert(_size != 0, "An allocation should always be requested with this operation.");
 186   AllocTracer::send_allocation_requiring_gc_event(_size * HeapWordSize, GCId::peek());
 187 }
 188 
 189 // Returns true iff concurrent GCs unloads metadata.
 190 bool VM_CollectForMetadataAllocation::initiate_concurrent_GC() {
 191 #if INCLUDE_G1GC
 192   if (UseG1GC && ClassUnloadingWithConcurrentMark) {
 193     G1CollectedHeap* g1h = G1CollectedHeap::heap();
 194     g1h->policy()->collector_state()->set_initiate_conc_mark_if_possible(true);
 195 
 196     GCCauseSetter x(g1h, _gc_cause);
 197 
 198     // At this point we are supposed to start a concurrent cycle. We
 199     // will do so if one is not already in progress.
 200     bool should_start = g1h->policy()->force_concurrent_start_if_outside_cycle(_gc_cause);
 201 
 202     if (should_start) {
 203       double pause_target = g1h->policy()->max_pause_time_ms();
 204       g1h->do_collection_pause_at_safepoint(pause_target);
 205     }
 206     return true;
 207   }
 208 #endif
 209 
 210   return false;
 211 }
 212 
 213 void VM_CollectForMetadataAllocation::doit() {
 214   SvcGCMarker sgcm(SvcGCMarker::FULL);
 215 
 216   CollectedHeap* heap = Universe::heap();
 217   GCCauseSetter gccs(heap, _gc_cause);
 218 
 219   // Check again if the space is available.  Another thread
 220   // may have similarly failed a metadata allocation and induced
 221   // a GC that freed space for the allocation.
 222   if (!MetadataAllocationFailALot) {
 223     _result = _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
 224     if (_result != NULL) {
 225       return;
 226     }
 227   }
 228 
 229   if (initiate_concurrent_GC()) {
 230     // For G1 expand since the collection is going to be concurrent.
 231     _result = _loader_data->metaspace_non_null()->expand_and_allocate(_size, _mdtype);
 232     if (_result != NULL) {
 233       return;
 234     }
 235 
 236     log_debug(gc)("G1 full GC for Metaspace");
 237   }
 238 
 239   // Don't clear the soft refs yet.
 240   heap->collect_as_vm_thread(GCCause::_metadata_GC_threshold);
 241   // After a GC try to allocate without expanding.  Could fail
 242   // and expansion will be tried below.
 243   _result = _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
 244   if (_result != NULL) {
 245     return;
 246   }
 247 
 248   // If still failing, allow the Metaspace to expand.
 249   // See delta_capacity_until_GC() for explanation of the
 250   // amount of the expansion.
 251   // This should work unless there really is no more space
 252   // or a MaxMetaspaceSize has been specified on the command line.
 253   _result = _loader_data->metaspace_non_null()->expand_and_allocate(_size, _mdtype);
 254   if (_result != NULL) {
 255     return;
 256   }
 257 
 258   // If expansion failed, do a collection clearing soft references.
 259   heap->collect_as_vm_thread(GCCause::_metadata_GC_clear_soft_refs);
 260   _result = _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
 261   if (_result != NULL) {
 262     return;
 263   }
 264 
 265   log_debug(gc)("After Metaspace GC failed to allocate size " SIZE_FORMAT, _size);
 266 
 267   if (GCLocker::is_active_and_needs_gc()) {
 268     set_gc_locked();
 269   }
 270 }
 271 
 272 VM_CollectForAllocation::VM_CollectForAllocation(size_t word_size, uint gc_count_before, GCCause::Cause cause)
 273     : VM_GC_Operation(gc_count_before, cause), _word_size(word_size), _result(NULL) {
 274   // Only report if operation was really caused by an allocation.
 275   if (_word_size != 0) {
 276     AllocTracer::send_allocation_requiring_gc_event(_word_size * HeapWordSize, GCId::peek());
 277   }
 278 }