1 /*
   2  * Copyright (c) 2005, 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 "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.inline.hpp"
  31 #include "gc/shared/genCollectedHeap.hpp"
  32 #include "gc/shared/vmGCOperations.hpp"
  33 #include "logging/log.hpp"
  34 #include "memory/oopFactory.hpp"
  35 #include "runtime/handles.inline.hpp"
  36 #include "runtime/init.hpp"
  37 #include "runtime/interfaceSupport.hpp"
  38 #include "utilities/dtrace.hpp"
  39 #include "utilities/macros.hpp"
  40 #include "utilities/preserveException.hpp"
  41 #if INCLUDE_ALL_GCS
  42 #include "gc/g1/g1CollectedHeap.inline.hpp"
  43 #endif // INCLUDE_ALL_GCS
  44 
  45 VM_GC_Operation::~VM_GC_Operation() {
  46   CollectedHeap* ch = Universe::heap();
  47   ch->collector_policy()->set_all_soft_refs_clear(false);
  48 }
  49 
  50 // The same dtrace probe can't be inserted in two different files, so we
  51 // have to call it here, so it's only in one file.  Can't create new probes
  52 // for the other file anymore.   The dtrace probes have to remain stable.
  53 void VM_GC_Operation::notify_gc_begin(bool full) {
  54   HOTSPOT_GC_BEGIN(
  55                    full);
  56   HS_DTRACE_WORKAROUND_TAIL_CALL_BUG();
  57 }
  58 
  59 void VM_GC_Operation::notify_gc_end() {
  60   HOTSPOT_GC_END();
  61   HS_DTRACE_WORKAROUND_TAIL_CALL_BUG();
  62 }
  63 
  64 void VM_GC_Operation::acquire_pending_list_lock() {
  65   _pending_list_locker.lock();
  66 }
  67 
  68 void VM_GC_Operation::release_and_notify_pending_list_lock() {
  69   _pending_list_locker.unlock();
  70 }
  71 
  72 // Allocations may fail in several threads at about the same time,
  73 // resulting in multiple gc requests.  We only want to do one of them.
  74 // In case a GC locker is active and the need for a GC is already signaled,
  75 // we want to skip this GC attempt altogether, without doing a futile
  76 // safepoint operation.
  77 bool VM_GC_Operation::skip_operation() const {
  78   bool skip = (_gc_count_before != Universe::heap()->total_collections());
  79   if (_full && skip) {
  80     skip = (_full_gc_count_before != Universe::heap()->total_full_collections());
  81   }
  82   if (!skip && GCLocker::is_active_and_needs_gc()) {
  83     skip = Universe::heap()->is_maximal_no_gc();
  84     assert(!(skip && (_gc_cause == GCCause::_gc_locker)),
  85            "GCLocker cannot be active when initiating GC");
  86   }
  87   return skip;
  88 }
  89 
  90 bool VM_GC_Operation::doit_prologue() {
  91   assert(Thread::current()->is_Java_thread(), "just checking");
  92   assert(((_gc_cause != GCCause::_no_gc) &&
  93           (_gc_cause != GCCause::_no_cause_specified)), "Illegal GCCause");
  94 
  95   // To be able to handle a GC the VM initialization needs to be completed.
  96   if (!is_init_completed()) {
  97     vm_exit_during_initialization(
  98       err_msg("GC triggered before VM initialization completed. Try increasing "
  99               "NewSize, current value " SIZE_FORMAT "%s.",
 100               byte_size_in_proper_unit(NewSize),
 101               proper_unit_for_byte_size(NewSize)));
 102   }
 103 
 104   acquire_pending_list_lock();
 105   // If the GC count has changed someone beat us to the collection
 106   // Get the Heap_lock after the pending_list_lock.
 107   Heap_lock->lock();
 108 
 109   // Check invocations
 110   if (skip_operation()) {
 111     // skip collection
 112     Heap_lock->unlock();
 113     release_and_notify_pending_list_lock();
 114     _prologue_succeeded = false;
 115   } else {
 116     _prologue_succeeded = true;
 117   }
 118   return _prologue_succeeded;
 119 }
 120 
 121 
 122 void VM_GC_Operation::doit_epilogue() {
 123   assert(Thread::current()->is_Java_thread(), "just checking");
 124   // Release the Heap_lock first.
 125   Heap_lock->unlock();
 126   release_and_notify_pending_list_lock();
 127 }
 128 
 129 bool VM_GC_HeapInspection::skip_operation() const {
 130   return false;
 131 }
 132 
 133 bool VM_GC_HeapInspection::collect() {
 134   if (GCLocker::is_active()) {
 135     return false;
 136   }
 137   Universe::heap()->collect_as_vm_thread(GCCause::_heap_inspection);
 138   return true;
 139 }
 140 
 141 void VM_GC_HeapInspection::doit() {
 142   HandleMark hm;
 143   Universe::heap()->ensure_parsability(false); // must happen, even if collection does
 144                                                // not happen (e.g. due to GCLocker)
 145                                                // or _full_gc being false
 146   if (_full_gc) {
 147     if (!collect()) {
 148       // The collection attempt was skipped because the gc locker is held.
 149       // The following dump may then be a tad misleading to someone expecting
 150       // only live objects to show up in the dump (see CR 6944195). Just issue
 151       // a suitable warning in that case and do not attempt to do a collection.
 152       // The latter is a subtle point, because even a failed attempt
 153       // to GC will, in fact, induce one in the future, which we
 154       // probably want to avoid in this case because the GC that we may
 155       // be about to attempt holds value for us only
 156       // if it happens now and not if it happens in the eventual
 157       // future.
 158       log_warning(gc)("GC locker is held; pre-dump GC was skipped");
 159     }
 160   }
 161   HeapInspection inspect(_csv_format, _print_help, _print_class_stats,
 162                          _columns);
 163   inspect.heap_inspection(_out);
 164 }
 165 
 166 
 167 void VM_GenCollectForAllocation::doit() {
 168   SvcGCMarker sgcm(SvcGCMarker::MINOR);
 169 
 170   GenCollectedHeap* gch = GenCollectedHeap::heap();
 171   GCCauseSetter gccs(gch, _gc_cause);
 172   _result = gch->satisfy_failed_allocation(_word_size, _tlab);
 173   assert(gch->is_in_reserved_or_null(_result), "result not in heap");
 174 
 175   if (_result == NULL && GCLocker::is_active_and_needs_gc()) {
 176     set_gc_locked();
 177   }
 178 }
 179 
 180 void VM_GenCollectFull::doit() {
 181   SvcGCMarker sgcm(SvcGCMarker::FULL);
 182 
 183   GenCollectedHeap* gch = GenCollectedHeap::heap();
 184   GCCauseSetter gccs(gch, _gc_cause);
 185   gch->do_full_collection(gch->must_clear_all_soft_refs(), _max_generation);
 186 }
 187 
 188 VM_CollectForMetadataAllocation::VM_CollectForMetadataAllocation(ClassLoaderData* loader_data,
 189                                                                  size_t size,
 190                                                                  Metaspace::MetadataType mdtype,
 191                                                                  uint gc_count_before,
 192                                                                  uint full_gc_count_before,
 193                                                                  GCCause::Cause gc_cause)
 194     : VM_GC_Operation(gc_count_before, gc_cause, full_gc_count_before, true),
 195       _loader_data(loader_data), _size(size), _mdtype(mdtype), _result(NULL) {
 196   assert(_size != 0, "An allocation should always be requested with this operation.");
 197   AllocTracer::send_allocation_requiring_gc_event(_size * HeapWordSize, GCId::peek());
 198 }
 199 
 200 // Returns true iff concurrent GCs unloads metadata.
 201 bool VM_CollectForMetadataAllocation::initiate_concurrent_GC() {
 202 #if INCLUDE_ALL_GCS
 203   if (UseConcMarkSweepGC && CMSClassUnloadingEnabled) {
 204     MetaspaceGC::set_should_concurrent_collect(true);
 205     return true;
 206   }
 207 
 208   if (UseG1GC && ClassUnloadingWithConcurrentMark) {
 209     G1CollectedHeap* g1h = G1CollectedHeap::heap();
 210     g1h->g1_policy()->collector_state()->set_initiate_conc_mark_if_possible(true);
 211 
 212     GCCauseSetter x(g1h, _gc_cause);
 213 
 214     // At this point we are supposed to start a concurrent cycle. We
 215     // will do so if one is not already in progress.
 216     bool should_start = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause);
 217 
 218     if (should_start) {
 219       double pause_target = g1h->g1_policy()->max_pause_time_ms();
 220       g1h->do_collection_pause_at_safepoint(pause_target);
 221     }
 222     return true;
 223   }
 224 #endif
 225 
 226   return false;
 227 }
 228 
 229 void VM_CollectForMetadataAllocation::doit() {
 230   SvcGCMarker sgcm(SvcGCMarker::FULL);
 231 
 232   CollectedHeap* heap = Universe::heap();
 233   GCCauseSetter gccs(heap, _gc_cause);
 234 
 235   // Check again if the space is available.  Another thread
 236   // may have similarly failed a metadata allocation and induced
 237   // a GC that freed space for the allocation.
 238   if (!MetadataAllocationFailALot) {
 239     _result = _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
 240     if (_result != NULL) {
 241       return;
 242     }
 243   }
 244 
 245   if (initiate_concurrent_GC()) {
 246     // For CMS and G1 expand since the collection is going to be concurrent.
 247     _result = _loader_data->metaspace_non_null()->expand_and_allocate(_size, _mdtype);
 248     if (_result != NULL) {
 249       return;
 250     }
 251 
 252     log_debug(gc)("%s full GC for Metaspace", UseConcMarkSweepGC ? "CMS" : "G1");
 253   }
 254 
 255   // Don't clear the soft refs yet.
 256   heap->collect_as_vm_thread(GCCause::_metadata_GC_threshold);
 257   // After a GC try to allocate without expanding.  Could fail
 258   // and expansion will be tried below.
 259   _result = _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
 260   if (_result != NULL) {
 261     return;
 262   }
 263 
 264   // If still failing, allow the Metaspace to expand.
 265   // See delta_capacity_until_GC() for explanation of the
 266   // amount of the expansion.
 267   // This should work unless there really is no more space
 268   // or a MaxMetaspaceSize has been specified on the command line.
 269   _result = _loader_data->metaspace_non_null()->expand_and_allocate(_size, _mdtype);
 270   if (_result != NULL) {
 271     return;
 272   }
 273 
 274   // If expansion failed, do a collection clearing soft references.
 275   heap->collect_as_vm_thread(GCCause::_metadata_GC_clear_soft_refs);
 276   _result = _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
 277   if (_result != NULL) {
 278     return;
 279   }
 280 
 281   log_debug(gc)("After Metaspace GC failed to allocate size " SIZE_FORMAT, _size);
 282 
 283   if (GCLocker::is_active_and_needs_gc()) {
 284     set_gc_locked();
 285   }
 286 }
 287 
 288 VM_CollectForAllocation::VM_CollectForAllocation(size_t word_size, uint gc_count_before, GCCause::Cause cause)
 289     : VM_GC_Operation(gc_count_before, cause), _result(NULL), _word_size(word_size) {
 290   // Only report if operation was really caused by an allocation.
 291   if (_word_size != 0) {
 292     AllocTracer::send_allocation_requiring_gc_event(_word_size * HeapWordSize, GCId::peek());
 293   }
 294 }