1 /*
   2  * Copyright (c) 2005, 2017, 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 "interpreter/oopMapCache.hpp"
  34 #include "logging/log.hpp"
  35 #include "memory/oopFactory.hpp"
  36 #include "runtime/handles.inline.hpp"
  37 #include "runtime/init.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 #include "gc/g1/g1Policy.hpp"
  44 #endif // INCLUDE_ALL_GCS
  45 
  46 VM_GC_Operation::~VM_GC_Operation() {
  47   CollectedHeap* ch = Universe::heap();
  48   ch->soft_ref_policy()->set_all_soft_refs_clear(false);
  49 }
  50 
  51 // The same dtrace probe can't be inserted in two different files, so we
  52 // have to call it here, so it's only in one file.  Can't create new probes
  53 // for the other file anymore.   The dtrace probes have to remain stable.
  54 void VM_GC_Operation::notify_gc_begin(bool full) {
  55   HOTSPOT_GC_BEGIN(
  56                    full);
  57   HS_DTRACE_WORKAROUND_TAIL_CALL_BUG();
  58 }
  59 
  60 void VM_GC_Operation::notify_gc_end() {
  61   HOTSPOT_GC_END();
  62   HS_DTRACE_WORKAROUND_TAIL_CALL_BUG();
  63 }
  64 
  65 // Allocations may fail in several threads at about the same time,
  66 // resulting in multiple gc requests.  We only want to do one of them.
  67 // In case a GC locker is active and the need for a GC is already signaled,
  68 // we want to skip this GC attempt altogether, without doing a futile
  69 // safepoint operation.
  70 bool VM_GC_Operation::skip_operation() const {
  71   bool skip = (_gc_count_before != Universe::heap()->total_collections());
  72   if (_full && skip) {
  73     skip = (_full_gc_count_before != Universe::heap()->total_full_collections());
  74   }
  75   if (!skip && GCLocker::is_active_and_needs_gc()) {
  76     skip = Universe::heap()->is_maximal_no_gc();
  77     assert(!(skip && (_gc_cause == GCCause::_gc_locker)),
  78            "GCLocker cannot be active when initiating GC");
  79   }
  80   return skip;
  81 }
  82 
  83 bool VM_GC_Operation::doit_prologue() {
  84   assert(Thread::current()->is_Java_thread(), "just checking");
  85   assert(((_gc_cause != GCCause::_no_gc) &&
  86           (_gc_cause != GCCause::_no_cause_specified)), "Illegal GCCause");
  87 
  88   // To be able to handle a GC the VM initialization needs to be completed.
  89   if (!is_init_completed()) {
  90     vm_exit_during_initialization(
  91       err_msg("GC triggered before VM initialization completed. Try increasing "
  92               "NewSize, current value " SIZE_FORMAT "%s.",
  93               byte_size_in_proper_unit(NewSize),
  94               proper_unit_for_byte_size(NewSize)));
  95   }
  96 
  97   // If the GC count has changed someone beat us to the collection
  98   Heap_lock->lock();
  99 
 100   // Check invocations
 101   if (skip_operation()) {
 102     // skip collection
 103     Heap_lock->unlock();
 104     _prologue_succeeded = false;
 105   } else {
 106     _prologue_succeeded = true;
 107   }
 108   return _prologue_succeeded;
 109 }
 110 
 111 
 112 void VM_GC_Operation::doit_epilogue() {
 113   assert(Thread::current()->is_Java_thread(), "just checking");
 114   // Clean up old interpreter OopMap entries that were replaced
 115   // during the GC thread root traversal.
 116   OopMapCache::cleanup_old_entries();
 117   if (Universe::has_reference_pending_list()) {
 118     Heap_lock->notify_all();
 119   }
 120   Heap_lock->unlock();
 121 }
 122 
 123 bool VM_GC_HeapInspection::skip_operation() const {
 124   return false;
 125 }
 126 
 127 bool VM_GC_HeapInspection::collect() {
 128   if (GCLocker::is_active()) {
 129     return false;
 130   }
 131   Universe::heap()->collect_as_vm_thread(GCCause::_heap_inspection);
 132   return true;
 133 }
 134 
 135 void VM_GC_HeapInspection::doit() {
 136   HandleMark hm;
 137   Universe::heap()->ensure_parsability(false); // must happen, even if collection does
 138                                                // not happen (e.g. due to GCLocker)
 139                                                // or _full_gc being false
 140   if (_full_gc) {
 141     if (!collect()) {
 142       // The collection attempt was skipped because the gc locker is held.
 143       // The following dump may then be a tad misleading to someone expecting
 144       // only live objects to show up in the dump (see CR 6944195). Just issue
 145       // a suitable warning in that case and do not attempt to do a collection.
 146       // The latter is a subtle point, because even a failed attempt
 147       // to GC will, in fact, induce one in the future, which we
 148       // probably want to avoid in this case because the GC that we may
 149       // be about to attempt holds value for us only
 150       // if it happens now and not if it happens in the eventual
 151       // future.
 152       log_warning(gc)("GC locker is held; pre-dump GC was skipped");
 153     }
 154   }
 155   HeapInspection inspect(_csv_format, _print_help, _print_class_stats,
 156                          _columns);
 157   inspect.heap_inspection(_out);
 158 }
 159 
 160 
 161 void VM_GenCollectForAllocation::doit() {
 162   SvcGCMarker sgcm(SvcGCMarker::MINOR);
 163 
 164   GenCollectedHeap* gch = GenCollectedHeap::heap();
 165   GCCauseSetter gccs(gch, _gc_cause);
 166   _result = gch->satisfy_failed_allocation(_word_size, _tlab);
 167   assert(gch->is_in_reserved_or_null(_result), "result not in heap");
 168 
 169   if (_result == NULL && GCLocker::is_active_and_needs_gc()) {
 170     set_gc_locked();
 171   }
 172 }
 173 
 174 void VM_GenCollectFull::doit() {
 175   SvcGCMarker sgcm(SvcGCMarker::FULL);
 176 
 177   GenCollectedHeap* gch = GenCollectedHeap::heap();
 178   GCCauseSetter gccs(gch, _gc_cause);
 179   gch->do_full_collection(gch->must_clear_all_soft_refs(), _max_generation);
 180 }
 181 
 182 VM_CollectForMetadataAllocation::VM_CollectForMetadataAllocation(ClassLoaderData* loader_data,
 183                                                                  size_t size,
 184                                                                  Metaspace::MetadataType mdtype,
 185                                                                  uint gc_count_before,
 186                                                                  uint full_gc_count_before,
 187                                                                  GCCause::Cause gc_cause)
 188     : VM_GC_Operation(gc_count_before, gc_cause, full_gc_count_before, true),
 189       _loader_data(loader_data), _size(size), _mdtype(mdtype), _result(NULL) {
 190   assert(_size != 0, "An allocation should always be requested with this operation.");
 191   AllocTracer::send_allocation_requiring_gc_event(_size * HeapWordSize, GCId::peek());
 192 }
 193 
 194 // Returns true iff concurrent GCs unloads metadata.
 195 bool VM_CollectForMetadataAllocation::initiate_concurrent_GC() {
 196 #if INCLUDE_ALL_GCS
 197   if (UseConcMarkSweepGC && CMSClassUnloadingEnabled) {
 198     MetaspaceGC::set_should_concurrent_collect(true);
 199     return true;
 200   }
 201 
 202   if (UseG1GC && ClassUnloadingWithConcurrentMark) {
 203     G1CollectedHeap* g1h = G1CollectedHeap::heap();
 204     g1h->g1_policy()->collector_state()->set_initiate_conc_mark_if_possible(true);
 205 
 206     GCCauseSetter x(g1h, _gc_cause);
 207 
 208     // At this point we are supposed to start a concurrent cycle. We
 209     // will do so if one is not already in progress.
 210     bool should_start = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause);
 211 
 212     if (should_start) {
 213       double pause_target = g1h->g1_policy()->max_pause_time_ms();
 214       g1h->do_collection_pause_at_safepoint(pause_target);
 215     }
 216     return true;
 217   }
 218 #endif
 219 
 220   return false;
 221 }
 222 
 223 void VM_CollectForMetadataAllocation::doit() {
 224   SvcGCMarker sgcm(SvcGCMarker::FULL);
 225 
 226   CollectedHeap* heap = Universe::heap();
 227   GCCauseSetter gccs(heap, _gc_cause);
 228 
 229   // Check again if the space is available.  Another thread
 230   // may have similarly failed a metadata allocation and induced
 231   // a GC that freed space for the allocation.
 232   if (!MetadataAllocationFailALot) {
 233     _result = _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
 234     if (_result != NULL) {
 235       return;
 236     }
 237   }
 238 
 239   if (initiate_concurrent_GC()) {
 240     // For CMS and G1 expand since the collection is going to be concurrent.
 241     _result = _loader_data->metaspace_non_null()->expand_and_allocate(_size, _mdtype);
 242     if (_result != NULL) {
 243       return;
 244     }
 245 
 246     log_debug(gc)("%s full GC for Metaspace", UseConcMarkSweepGC ? "CMS" : "G1");
 247   }
 248 
 249   // Don't clear the soft refs yet.
 250   heap->collect_as_vm_thread(GCCause::_metadata_GC_threshold);
 251   // After a GC try to allocate without expanding.  Could fail
 252   // and expansion will be tried below.
 253   _result = _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
 254   if (_result != NULL) {
 255     return;
 256   }
 257 
 258   // If still failing, allow the Metaspace to expand.
 259   // See delta_capacity_until_GC() for explanation of the
 260   // amount of the expansion.
 261   // This should work unless there really is no more space
 262   // or a MaxMetaspaceSize has been specified on the command line.
 263   _result = _loader_data->metaspace_non_null()->expand_and_allocate(_size, _mdtype);
 264   if (_result != NULL) {
 265     return;
 266   }
 267 
 268   // If expansion failed, do a collection clearing soft references.
 269   heap->collect_as_vm_thread(GCCause::_metadata_GC_clear_soft_refs);
 270   _result = _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
 271   if (_result != NULL) {
 272     return;
 273   }
 274 
 275   log_debug(gc)("After Metaspace GC failed to allocate size " SIZE_FORMAT, _size);
 276 
 277   if (GCLocker::is_active_and_needs_gc()) {
 278     set_gc_locked();
 279   }
 280 }
 281 
 282 VM_CollectForAllocation::VM_CollectForAllocation(size_t word_size, uint gc_count_before, GCCause::Cause cause)
 283     : VM_GC_Operation(gc_count_before, cause), _result(NULL), _word_size(word_size) {
 284   // Only report if operation was really caused by an allocation.
 285   if (_word_size != 0) {
 286     AllocTracer::send_allocation_requiring_gc_event(_word_size * HeapWordSize, GCId::peek());
 287   }
 288 }
--- EOF ---