1 /*
   2  * Copyright (c) 2005, 2013, 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_implementation/shared/vmGCOperations.hpp"
  29 #include "memory/gcLocker.inline.hpp"
  30 #include "memory/genCollectedHeap.hpp"
  31 #include "memory/oopFactory.hpp"
  32 #include "oops/instanceKlass.hpp"
  33 #include "oops/instanceRefKlass.hpp"
  34 #include "runtime/handles.inline.hpp"
  35 #include "runtime/init.hpp"
  36 #include "runtime/interfaceSupport.hpp"
  37 #include "utilities/dtrace.hpp"
  38 #include "utilities/preserveException.hpp"
  39 #include "utilities/macros.hpp"
  40 #if INCLUDE_ALL_GCS
  41 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  42 #endif // INCLUDE_ALL_GCS
  43 
  44 #ifndef USDT2
  45 HS_DTRACE_PROBE_DECL1(hotspot, gc__begin, bool);
  46 HS_DTRACE_PROBE_DECL(hotspot, gc__end);
  47 #endif /* !USDT2 */
  48 
  49 // The same dtrace probe can't be inserted in two different files, so we
  50 // have to call it here, so it's only in one file.  Can't create new probes
  51 // for the other file anymore.   The dtrace probes have to remain stable.
  52 void VM_GC_Operation::notify_gc_begin(bool full) {
  53 #ifndef USDT2
  54   HS_DTRACE_PROBE1(hotspot, gc__begin, full);
  55   HS_DTRACE_WORKAROUND_TAIL_CALL_BUG();
  56 #else /* USDT2 */
  57   HOTSPOT_GC_BEGIN(
  58                    full);
  59 #endif /* USDT2 */
  60 }
  61 
  62 void VM_GC_Operation::notify_gc_end() {
  63 #ifndef USDT2
  64   HS_DTRACE_PROBE(hotspot, gc__end);
  65   HS_DTRACE_WORKAROUND_TAIL_CALL_BUG();
  66 #else /* USDT2 */
  67   HOTSPOT_GC_END(
  68 );
  69 #endif /* USDT2 */
  70 }
  71 
  72 void VM_GC_Operation::acquire_pending_list_lock() {
  73   // we may enter this with pending exception set
  74   InstanceRefKlass::acquire_pending_list_lock(&_pending_list_basic_lock);
  75 }
  76 
  77 
  78 void VM_GC_Operation::release_and_notify_pending_list_lock() {
  79 
  80   InstanceRefKlass::release_and_notify_pending_list_lock(&_pending_list_basic_lock);
  81 }
  82 
  83 // Allocations may fail in several threads at about the same time,
  84 // resulting in multiple gc requests.  We only want to do one of them.
  85 // In case a GC locker is active and the need for a GC is already signalled,
  86 // we want to skip this GC attempt altogether, without doing a futile
  87 // safepoint operation.
  88 bool VM_GC_Operation::skip_operation() const {
  89   bool skip = (_gc_count_before != Universe::heap()->total_collections());
  90   if (_full && skip) {
  91     skip = (_full_gc_count_before != Universe::heap()->total_full_collections());
  92   }
  93   if (!skip && GC_locker::is_active_and_needs_gc()) {
  94     skip = Universe::heap()->is_maximal_no_gc();
  95     assert(!(skip && (_gc_cause == GCCause::_gc_locker)),
  96            "GC_locker cannot be active when initiating GC");
  97   }
  98   return skip;
  99 }
 100 
 101 bool VM_GC_Operation::doit_prologue() {
 102   assert(Thread::current()->is_Java_thread(), "just checking");
 103   assert(((_gc_cause != GCCause::_no_gc) &&
 104           (_gc_cause != GCCause::_no_cause_specified)), "Illegal GCCause");
 105 
 106   acquire_pending_list_lock();
 107   // If the GC count has changed someone beat us to the collection
 108   // Get the Heap_lock after the pending_list_lock.
 109   Heap_lock->lock();
 110 
 111   // Check invocations
 112   if (skip_operation()) {
 113     // skip collection
 114     Heap_lock->unlock();
 115     release_and_notify_pending_list_lock();
 116     _prologue_succeeded = false;
 117   } else {
 118     _prologue_succeeded = true;
 119     SharedHeap* sh = SharedHeap::heap();
 120     if (sh != NULL) sh->_thread_holds_heap_lock_for_gc = true;
 121   }
 122   return _prologue_succeeded;
 123 }
 124 
 125 
 126 void VM_GC_Operation::doit_epilogue() {
 127   assert(Thread::current()->is_Java_thread(), "just checking");
 128   // Release the Heap_lock first.
 129   SharedHeap* sh = SharedHeap::heap();
 130   if (sh != NULL) sh->_thread_holds_heap_lock_for_gc = false;
 131   Heap_lock->unlock();
 132   release_and_notify_pending_list_lock();
 133 }
 134 
 135 bool VM_GC_HeapInspection::doit_prologue() {
 136   if (Universe::heap()->supports_heap_inspection()) {
 137     return VM_GC_Operation::doit_prologue();
 138   } else {
 139     return false;
 140   }
 141 }
 142 
 143 bool VM_GC_HeapInspection::skip_operation() const {
 144   assert(Universe::heap()->supports_heap_inspection(), "huh?");
 145   return false;
 146 }
 147 
 148 bool VM_GC_HeapInspection::collect() {
 149   if (GC_locker::is_active()) {
 150     return false;
 151   }
 152   Universe::heap()->collect_as_vm_thread(GCCause::_heap_inspection);
 153   return true;
 154 }
 155 
 156 void VM_GC_HeapInspection::doit() {
 157   HandleMark hm;
 158   Universe::heap()->ensure_parsability(false); // must happen, even if collection does
 159                                                // not happen (e.g. due to GC_locker)
 160                                                // or _full_gc being false
 161   if (_full_gc) {
 162     if (!collect()) {
 163       // The collection attempt was skipped because the gc locker is held.
 164       // The following dump may then be a tad misleading to someone expecting
 165       // only live objects to show up in the dump (see CR 6944195). Just issue
 166       // a suitable warning in that case and do not attempt to do a collection.
 167       // The latter is a subtle point, because even a failed attempt
 168       // to GC will, in fact, induce one in the future, which we
 169       // probably want to avoid in this case because the GC that we may
 170       // be about to attempt holds value for us only
 171       // if it happens now and not if it happens in the eventual
 172       // future.
 173       warning("GC locker is held; pre-dump GC was skipped");
 174     }
 175   }
 176   HeapInspection inspect(_csv_format, _print_help, _print_class_stats,
 177                          _columns);
 178   inspect.heap_inspection(_out);
 179 }
 180 
 181 
 182 void VM_GenCollectForAllocation::doit() {
 183   SvcGCMarker sgcm(SvcGCMarker::MINOR);
 184 
 185   GenCollectedHeap* gch = GenCollectedHeap::heap();
 186   GCCauseSetter gccs(gch, _gc_cause);
 187   _res = gch->satisfy_failed_allocation(_size, _tlab);
 188   assert(gch->is_in_reserved_or_null(_res), "result not in heap");
 189 
 190   if (_res == NULL && GC_locker::is_active_and_needs_gc()) {
 191     set_gc_locked();
 192   }
 193 }
 194 
 195 void VM_GenCollectFull::doit() {
 196   SvcGCMarker sgcm(SvcGCMarker::FULL);
 197 
 198   GenCollectedHeap* gch = GenCollectedHeap::heap();
 199   GCCauseSetter gccs(gch, _gc_cause);
 200   gch->do_full_collection(gch->must_clear_all_soft_refs(), _max_level);
 201 }
 202 
 203 void VM_CollectForMetadataAllocation::doit() {
 204   SvcGCMarker sgcm(SvcGCMarker::FULL);
 205 
 206   CollectedHeap* heap = Universe::heap();
 207   GCCauseSetter gccs(heap, _gc_cause);
 208 
 209   // Check again if the space is available.  Another thread
 210   // may have similarly failed a metadata allocation and induced
 211   // a GC that freed space for the allocation.
 212   if (!MetadataAllocationFailALot) {
 213     _result = _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
 214     }
 215 
 216   if (_result == NULL) {
 217     if (UseConcMarkSweepGC) {
 218       if (CMSClassUnloadingEnabled) {
 219         MetaspaceGC::set_should_concurrent_collect(true);
 220       }
 221       // For CMS expand since the collection is going to be concurrent.
 222       _result =
 223         _loader_data->metaspace_non_null()->expand_and_allocate(_size, _mdtype);
 224     }
 225     if (_result == NULL) {
 226       // Don't clear the soft refs.  This GC is for reclaiming metadata
 227       // and is unrelated to the fullness of the Java heap which should
 228       // be the criteria for clearing SoftReferences.
 229       if (Verbose && PrintGCDetails && UseConcMarkSweepGC) {
 230         gclog_or_tty->print_cr("\nCMS full GC for Metaspace");
 231       }
 232       heap->collect_as_vm_thread(GCCause::_metadata_GC_threshold);
 233       // After a GC try to allocate without expanding.  Could fail
 234       // and expansion will be tried below.
 235       _result =
 236         _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
 237     }
 238     if (_result == NULL && !UseConcMarkSweepGC /* CMS already tried */) {
 239       // If still failing, allow the Metaspace to expand.
 240       // See delta_capacity_until_GC() for explanation of the
 241       // amount of the expansion.
 242       // This should work unless there really is no more space
 243       // or a MaxMetaspaceSize has been specified on the command line.
 244       _result =
 245         _loader_data->metaspace_non_null()->expand_and_allocate(_size, _mdtype);
 246 
 247     }
 248     if (Verbose && PrintGCDetails && _result == NULL) {
 249       gclog_or_tty->print_cr("\nAfter Metaspace GC failed to allocate size "
 250                              SIZE_FORMAT, _size);
 251     }
 252   }
 253 
 254   if (_result == NULL && GC_locker::is_active_and_needs_gc()) {
 255     set_gc_locked();
 256   }
 257 }