1/*
2 * Copyright (c) 2001, 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.
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23 */
24
25#include "precompiled.hpp"
26#include "classfile/javaClasses.hpp"
27#include "classfile/symbolTable.hpp"
28#include "classfile/systemDictionary.hpp"
29#include "classfile/vmSymbols.hpp"
30#include "code/codeCache.hpp"
31#include "code/icBuffer.hpp"
32#include "gc/g1/g1MarkSweep.hpp"
33#include "gc/g1/g1RootProcessor.hpp"
34#include "gc/g1/g1StringDedup.hpp"
35#include "gc/serial/markSweep.inline.hpp"
36#include "gc/shared/gcHeapSummary.hpp"
37#include "gc/shared/gcLocker.hpp"
38#include "gc/shared/gcTimer.hpp"
39#include "gc/shared/gcTrace.hpp"
40#include "gc/shared/gcTraceTime.inline.hpp"
41#include "gc/shared/genCollectedHeap.hpp"
42#include "gc/shared/modRefBarrierSet.hpp"
43#include "gc/shared/referencePolicy.hpp"
44#include "gc/shared/space.hpp"
45#include "oops/instanceRefKlass.hpp"
46#include "oops/oop.inline.hpp"
47#include "prims/jvmtiExport.hpp"
48#include "runtime/atomic.hpp"
49#include "runtime/biasedLocking.hpp"
50#include "runtime/fprofiler.hpp"
51#include "runtime/synchronizer.hpp"
52#include "runtime/thread.hpp"
53#include "runtime/vmThread.hpp"
54#include "utilities/copy.hpp"
55#include "utilities/events.hpp"
56
57class HeapRegion;
58
59bool G1MarkSweep::_archive_check_enabled = false;
60G1ArchiveRegionMap G1MarkSweep::_archive_region_map;
61
62void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
63                                      bool clear_all_softrefs) {
64  assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
65
66#ifdef ASSERT
67  if (G1CollectedHeap::heap()->collector_policy()->should_clear_all_soft_refs()) {
68    assert(clear_all_softrefs, "Policy should have been checked earler");
69  }
70#endif
71  // hook up weak ref data so it can be used during Mark-Sweep
72  assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
73  assert(rp != NULL, "should be non-NULL");
74  assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition");
75
76  GenMarkSweep::set_ref_processor(rp);
77  rp->setup_policy(clear_all_softrefs);
78
79  // When collecting the permanent generation Method*s may be moving,
80  // so we either have to flush all bcp data or convert it into bci.
81  CodeCache::gc_prologue();
82
83  bool marked_for_unloading = false;
84
85  allocate_stacks();
86
87  // We should save the marks of the currently locked biased monitors.
88  // The marking doesn't preserve the marks of biased objects.
89  BiasedLocking::preserve_marks();
90
91  mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
92
93  mark_sweep_phase2();
94
95#if defined(COMPILER2) || INCLUDE_JVMCI
96  // Don't add any more derived pointers during phase3
97  DerivedPointerTable::set_active(false);
98#endif
99
100  mark_sweep_phase3();
101
102  mark_sweep_phase4();
103
104  GenMarkSweep::restore_marks();
105  BiasedLocking::restore_marks();
106  GenMarkSweep::deallocate_stacks();
107
108  CodeCache::gc_epilogue();
109  JvmtiExport::gc_epilogue();
110
111  // refs processing: clean slate
112  GenMarkSweep::set_ref_processor(NULL);
113}
114
115
116void G1MarkSweep::allocate_stacks() {
117  GenMarkSweep::_preserved_count_max = 0;
118  GenMarkSweep::_preserved_marks = NULL;
119  GenMarkSweep::_preserved_count = 0;
120}
121
122void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
123                                    bool clear_all_softrefs) {
124  // Recursively traverse all live objects and mark them
125  GCTraceTime(Info, gc, phases) tm("Phase 1: Mark live objects", gc_timer());
126
127  G1CollectedHeap* g1h = G1CollectedHeap::heap();
128
129  // Need cleared claim bits for the roots processing
130  ClassLoaderDataGraph::clear_claimed_marks();
131
132  MarkingCodeBlobClosure follow_code_closure(&GenMarkSweep::follow_root_closure, !CodeBlobToOopClosure::FixRelocations);
133  {
134    G1RootProcessor root_processor(g1h, 1);
135    if (ClassUnloading) {
136      root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure,
137                                          &GenMarkSweep::follow_cld_closure,
138                                          &follow_code_closure);
139    } else {
140      root_processor.process_all_roots_no_string_table(
141                                          &GenMarkSweep::follow_root_closure,
142                                          &GenMarkSweep::follow_cld_closure,
143                                          &follow_code_closure);
144    }
145  }
146
147  {
148    GCTraceTime(Debug, gc, phases) trace("Reference Processing", gc_timer());
149
150    // Process reference objects found during marking
151    ReferenceProcessor* rp = GenMarkSweep::ref_processor();
152    assert(rp == g1h->ref_processor_stw(), "Sanity");
153
154    rp->setup_policy(clear_all_softrefs);
155    const ReferenceProcessorStats& stats =
156        rp->process_discovered_references(&GenMarkSweep::is_alive,
157                                          &GenMarkSweep::keep_alive,
158                                          &GenMarkSweep::follow_stack_closure,
159                                          NULL,
160                                          gc_timer());
161    gc_tracer()->report_gc_reference_stats(stats);
162  }
163
164  // This is the point where the entire marking should have completed.
165  assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
166
167  if (ClassUnloading) {
168    GCTraceTime(Debug, gc, phases) trace("Class Unloading", gc_timer());
169
170    // Unload classes and purge the SystemDictionary.
171    bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
172
173    // Unload nmethods.
174    CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);
175
176    // Prune dead klasses from subklass/sibling/implementor lists.
177    Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);
178  }
179
180  {
181    GCTraceTime(Debug, gc, phases) trace("Scrub String and Symbol Tables", gc_timer());
182    // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.
183    g1h->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);
184  }
185
186  if (G1StringDedup::is_enabled()) {
187    GCTraceTime(Debug, gc, phases) trace("String Deduplication Unlink", gc_timer());
188    G1StringDedup::unlink(&GenMarkSweep::is_alive);
189  }
190
191  if (VerifyDuringGC) {
192    HandleMark hm;  // handle scope
193#if defined(COMPILER2) || INCLUDE_JVMCI
194    DerivedPointerTableDeactivate dpt_deact;
195#endif
196    g1h->prepare_for_verify();
197    // Note: we can verify only the heap here. When an object is
198    // marked, the previous value of the mark word (including
199    // identity hash values, ages, etc) is preserved, and the mark
200    // word is set to markOop::marked_value - effectively removing
201    // any hash values from the mark word. These hash values are
202    // used when verifying the dictionaries and so removing them
203    // from the mark word can make verification of the dictionaries
204    // fail. At the end of the GC, the original mark word values
205    // (including hash values) are restored to the appropriate
206    // objects.
207    GCTraceTime(Info, gc, verify)("During GC (full)");
208    g1h->verify(VerifyOption_G1UseMarkWord);
209  }
210
211  gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
212}
213
214
215void G1MarkSweep::mark_sweep_phase2() {
216  // Now all live objects are marked, compute the new object addresses.
217
218  // It is not required that we traverse spaces in the same order in
219  // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
220  // tracking expects us to do so. See comment under phase4.
221
222  GCTraceTime(Info, gc, phases) tm("Phase 2: Compute new object addresses", gc_timer());
223
224  prepare_compaction();
225}
226
227class G1AdjustPointersClosure: public HeapRegionClosure {
228 public:
229  bool doHeapRegion(HeapRegion* r) {
230    if (r->is_humongous()) {
231      if (r->is_starts_humongous()) {
232        // We must adjust the pointers on the single H object.
233        oop obj = oop(r->bottom());
234        // point all the oops to the new location
235        MarkSweep::adjust_pointers(obj);
236      }
237    } else if (!r->is_pinned()) {
238      // This really ought to be "as_CompactibleSpace"...
239      r->adjust_pointers();
240    }
241    return false;
242  }
243};
244
245void G1MarkSweep::mark_sweep_phase3() {
246  G1CollectedHeap* g1h = G1CollectedHeap::heap();
247
248  // Adjust the pointers to reflect the new locations
249  GCTraceTime(Info, gc, phases) tm("Phase 3: Adjust pointers", gc_timer());
250
251  // Need cleared claim bits for the roots processing
252  ClassLoaderDataGraph::clear_claimed_marks();
253
254  CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
255  {
256    G1RootProcessor root_processor(g1h, 1);
257    root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure,
258                                     &GenMarkSweep::adjust_cld_closure,
259                                     &adjust_code_closure);
260  }
261
262  assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
263  g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
264
265  // Now adjust pointers in remaining weak roots.  (All of which should
266  // have been cleared if they pointed to non-surviving objects.)
267  JNIHandles::weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
268
269  if (G1StringDedup::is_enabled()) {
270    G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);
271  }
272
273  GenMarkSweep::adjust_marks();
274
275  G1AdjustPointersClosure blk;
276  g1h->heap_region_iterate(&blk);
277}
278
279class G1SpaceCompactClosure: public HeapRegionClosure {
280public:
281  G1SpaceCompactClosure() {}
282
283  bool doHeapRegion(HeapRegion* hr) {
284    if (hr->is_humongous()) {
285      if (hr->is_starts_humongous()) {
286        oop obj = oop(hr->bottom());
287        if (obj->is_gc_marked()) {
288          obj->init_mark();
289        } else {
290          assert(hr->is_empty(), "Should have been cleared in phase 2.");
291        }
292      }
293      hr->reset_during_compaction();
294    } else if (!hr->is_pinned()) {
295      hr->compact();
296    }
297    return false;
298  }
299};
300
301void G1MarkSweep::mark_sweep_phase4() {
302  // All pointers are now adjusted, move objects accordingly
303
304  // The ValidateMarkSweep live oops tracking expects us to traverse spaces
305  // in the same order in phase2, phase3 and phase4. We don't quite do that
306  // here (code and comment not fixed for perm removal), so we tell the validate code
307  // to use a higher index (saved from phase2) when verifying perm_gen.
308  G1CollectedHeap* g1h = G1CollectedHeap::heap();
309
310  GCTraceTime(Info, gc, phases) tm("Phase 4: Move objects", gc_timer());
311
312  G1SpaceCompactClosure blk;
313  g1h->heap_region_iterate(&blk);
314
315}
316
317void G1MarkSweep::enable_archive_object_check() {
318  assert(!_archive_check_enabled, "archive range check already enabled");
319  _archive_check_enabled = true;
320  size_t length = Universe::heap()->max_capacity();
321  _archive_region_map.initialize((HeapWord*)Universe::heap()->base(),
322                                 (HeapWord*)Universe::heap()->base() + length,
323                                 HeapRegion::GrainBytes);
324}
325
326void G1MarkSweep::set_range_archive(MemRegion range, bool is_archive) {
327  assert(_archive_check_enabled, "archive range check not enabled");
328  _archive_region_map.set_by_address(range, is_archive);
329}
330
331bool G1MarkSweep::in_archive_range(oop object) {
332  // This is the out-of-line part of is_archive_object test, done separately
333  // to avoid additional performance impact when the check is not enabled.
334  return _archive_region_map.get_by_address((HeapWord*)object);
335}
336
337void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) {
338  G1CollectedHeap* g1h = G1CollectedHeap::heap();
339  g1h->heap_region_iterate(blk);
340  blk->update_sets();
341}
342
343void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) {
344  HeapWord* end = hr->end();
345  FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
346
347  hr->set_containing_set(NULL);
348  _humongous_regions_removed++;
349
350  _g1h->free_humongous_region(hr, &dummy_free_list, false /* skip_remset */);
351  prepare_for_compaction(hr, end);
352  dummy_free_list.remove_all();
353}
354
355void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) {
356  // If this is the first live region that we came across which we can compact,
357  // initialize the CompactPoint.
358  if (!is_cp_initialized()) {
359    _cp.space = hr;
360    _cp.threshold = hr->initialize_threshold();
361  }
362  prepare_for_compaction_work(&_cp, hr, end);
363}
364
365void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp,
366                                                          HeapRegion* hr,
367                                                          HeapWord* end) {
368  hr->prepare_for_compaction(cp);
369  // Also clear the part of the card table that will be unused after
370  // compaction.
371  _mrbs->clear(MemRegion(hr->compaction_top(), end));
372}
373
374void G1PrepareCompactClosure::update_sets() {
375  // We'll recalculate total used bytes and recreate the free list
376  // at the end of the GC, so no point in updating those values here.
377  _g1h->remove_from_old_sets(0, _humongous_regions_removed);
378}
379
380bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) {
381  if (hr->is_humongous()) {
382    oop obj = oop(hr->humongous_start_region()->bottom());
383    if (hr->is_starts_humongous() && obj->is_gc_marked()) {
384      obj->forward_to(obj);
385    }
386    if (!obj->is_gc_marked()) {
387      free_humongous_region(hr);
388    }
389  } else if (!hr->is_pinned()) {
390    prepare_for_compaction(hr, hr->end());
391  }
392  return false;
393}
394