1/*
2 * Copyright (c) 2001, 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/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/g1FullGCScope.hpp"
33#include "gc/g1/g1MarkSweep.hpp"
34#include "gc/g1/g1RootProcessor.hpp"
35#include "gc/g1/g1StringDedup.hpp"
36#include "gc/serial/markSweep.inline.hpp"
37#include "gc/shared/gcHeapSummary.hpp"
38#include "gc/shared/gcLocker.hpp"
39#include "gc/shared/gcTimer.hpp"
40#include "gc/shared/gcTrace.hpp"
41#include "gc/shared/gcTraceTime.inline.hpp"
42#include "gc/shared/genCollectedHeap.hpp"
43#include "gc/shared/modRefBarrierSet.hpp"
44#include "gc/shared/referencePolicy.hpp"
45#include "gc/shared/space.hpp"
46#include "oops/instanceRefKlass.hpp"
47#include "oops/oop.inline.hpp"
48#include "prims/jvmtiExport.hpp"
49#include "runtime/atomic.hpp"
50#include "runtime/biasedLocking.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
59void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
60                                      bool clear_all_softrefs) {
61  assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
62  HandleMark hm;  // Discard invalid handles created during gc
63
64#if defined(COMPILER2) || INCLUDE_JVMCI
65  DerivedPointerTable::clear();
66#endif
67#ifdef ASSERT
68  if (G1CollectedHeap::heap()->collector_policy()->should_clear_all_soft_refs()) {
69    assert(clear_all_softrefs, "Policy should have been checked earler");
70  }
71#endif
72  // hook up weak ref data so it can be used during Mark-Sweep
73  assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
74  assert(rp != NULL, "should be non-NULL");
75  assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition");
76
77  GenMarkSweep::set_ref_processor(rp);
78  rp->setup_policy(clear_all_softrefs);
79
80  // When collecting the permanent generation Method*s may be moving,
81  // so we either have to flush all bcp data or convert it into bci.
82  CodeCache::gc_prologue();
83
84  bool marked_for_unloading = false;
85
86  allocate_stacks();
87
88  // We should save the marks of the currently locked biased monitors.
89  // The marking doesn't preserve the marks of biased objects.
90  BiasedLocking::preserve_marks();
91
92  // Process roots and do the marking.
93  mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
94
95  // Prepare compaction.
96  mark_sweep_phase2();
97
98#if defined(COMPILER2) || INCLUDE_JVMCI
99  // Don't add any more derived pointers during phase3
100  DerivedPointerTable::set_active(false);
101#endif
102
103  // Adjust all pointers.
104  mark_sweep_phase3();
105
106  // Do the actual compaction.
107  mark_sweep_phase4();
108
109  GenMarkSweep::restore_marks();
110  BiasedLocking::restore_marks();
111  GenMarkSweep::deallocate_stacks();
112
113#if defined(COMPILER2) || INCLUDE_JVMCI
114  // Now update the derived pointers.
115  DerivedPointerTable::update_pointers();
116#endif
117
118  CodeCache::gc_epilogue();
119  JvmtiExport::gc_epilogue();
120
121  // refs processing: clean slate
122  GenMarkSweep::set_ref_processor(NULL);
123}
124
125STWGCTimer* G1MarkSweep::gc_timer() {
126  return G1FullGCScope::instance()->timer();
127}
128
129SerialOldTracer* G1MarkSweep::gc_tracer() {
130  return G1FullGCScope::instance()->tracer();
131}
132
133void G1MarkSweep::allocate_stacks() {
134  GenMarkSweep::_preserved_count_max = 0;
135  GenMarkSweep::_preserved_marks = NULL;
136  GenMarkSweep::_preserved_count = 0;
137}
138
139void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
140                                    bool clear_all_softrefs) {
141  // Recursively traverse all live objects and mark them
142  GCTraceTime(Info, gc, phases) tm("Phase 1: Mark live objects", gc_timer());
143
144  G1CollectedHeap* g1h = G1CollectedHeap::heap();
145
146  // Need cleared claim bits for the roots processing
147  ClassLoaderDataGraph::clear_claimed_marks();
148
149  MarkingCodeBlobClosure follow_code_closure(&GenMarkSweep::follow_root_closure, !CodeBlobToOopClosure::FixRelocations);
150  {
151    G1RootProcessor root_processor(g1h, 1);
152    if (ClassUnloading) {
153      root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure,
154                                          &GenMarkSweep::follow_cld_closure,
155                                          &follow_code_closure);
156    } else {
157      root_processor.process_all_roots_no_string_table(
158                                          &GenMarkSweep::follow_root_closure,
159                                          &GenMarkSweep::follow_cld_closure,
160                                          &follow_code_closure);
161    }
162  }
163
164  {
165    GCTraceTime(Debug, gc, phases) trace("Reference Processing", gc_timer());
166
167    // Process reference objects found during marking
168    ReferenceProcessor* rp = GenMarkSweep::ref_processor();
169    assert(rp == g1h->ref_processor_stw(), "Sanity");
170
171    rp->setup_policy(clear_all_softrefs);
172    ReferenceProcessorPhaseTimes pt(gc_timer(), rp->num_q());
173
174    const ReferenceProcessorStats& stats =
175        rp->process_discovered_references(&GenMarkSweep::is_alive,
176                                          &GenMarkSweep::keep_alive,
177                                          &GenMarkSweep::follow_stack_closure,
178                                          NULL,
179                                          &pt);
180    gc_tracer()->report_gc_reference_stats(stats);
181    pt.print_all_references();
182  }
183
184  // This is the point where the entire marking should have completed.
185  assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
186
187  if (ClassUnloading) {
188    GCTraceTime(Debug, gc, phases) trace("Class Unloading", gc_timer());
189
190    // Unload classes and purge the SystemDictionary.
191    bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive, gc_timer());
192
193    g1h->complete_cleaning(&GenMarkSweep::is_alive, purged_class);
194  } else {
195    GCTraceTime(Debug, gc, phases) trace("Cleanup", gc_timer());
196    g1h->partial_cleaning(&GenMarkSweep::is_alive, true, true, G1StringDedup::is_enabled());
197  }
198
199  if (VerifyDuringGC) {
200    HandleMark hm;  // handle scope
201#if defined(COMPILER2) || INCLUDE_JVMCI
202    DerivedPointerTableDeactivate dpt_deact;
203#endif
204    g1h->prepare_for_verify();
205    // Note: we can verify only the heap here. When an object is
206    // marked, the previous value of the mark word (including
207    // identity hash values, ages, etc) is preserved, and the mark
208    // word is set to markOop::marked_value - effectively removing
209    // any hash values from the mark word. These hash values are
210    // used when verifying the dictionaries and so removing them
211    // from the mark word can make verification of the dictionaries
212    // fail. At the end of the GC, the original mark word values
213    // (including hash values) are restored to the appropriate
214    // objects.
215    GCTraceTime(Info, gc, verify)("During GC (full)");
216    g1h->verify(VerifyOption_G1UseMarkWord);
217  }
218
219  gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
220}
221
222
223void G1MarkSweep::mark_sweep_phase2() {
224  // Now all live objects are marked, compute the new object addresses.
225
226  // It is not required that we traverse spaces in the same order in
227  // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
228  // tracking expects us to do so. See comment under phase4.
229
230  GCTraceTime(Info, gc, phases) tm("Phase 2: Compute new object addresses", gc_timer());
231
232  prepare_compaction();
233}
234
235class G1AdjustPointersClosure: public HeapRegionClosure {
236 public:
237  bool doHeapRegion(HeapRegion* r) {
238    if (r->is_humongous()) {
239      if (r->is_starts_humongous()) {
240        // We must adjust the pointers on the single H object.
241        oop obj = oop(r->bottom());
242        // point all the oops to the new location
243        MarkSweep::adjust_pointers(obj);
244      }
245    } else if (!r->is_closed_archive()) {
246      // This really ought to be "as_CompactibleSpace"...
247      r->adjust_pointers();
248    }
249    return false;
250  }
251};
252
253void G1MarkSweep::mark_sweep_phase3() {
254  G1CollectedHeap* g1h = G1CollectedHeap::heap();
255
256  // Adjust the pointers to reflect the new locations
257  GCTraceTime(Info, gc, phases) tm("Phase 3: Adjust pointers", gc_timer());
258
259  // Need cleared claim bits for the roots processing
260  ClassLoaderDataGraph::clear_claimed_marks();
261
262  CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
263  {
264    G1RootProcessor root_processor(g1h, 1);
265    root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure,
266                                     &GenMarkSweep::adjust_cld_closure,
267                                     &adjust_code_closure);
268  }
269
270  assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
271  g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
272
273  // Now adjust pointers in remaining weak roots.  (All of which should
274  // have been cleared if they pointed to non-surviving objects.)
275  JNIHandles::weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
276
277  if (G1StringDedup::is_enabled()) {
278    G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);
279  }
280
281  GenMarkSweep::adjust_marks();
282
283  G1AdjustPointersClosure blk;
284  g1h->heap_region_iterate(&blk);
285}
286
287class G1SpaceCompactClosure: public HeapRegionClosure {
288public:
289  G1SpaceCompactClosure() {}
290
291  bool doHeapRegion(HeapRegion* hr) {
292    if (hr->is_humongous()) {
293      if (hr->is_starts_humongous()) {
294        oop obj = oop(hr->bottom());
295        if (obj->is_gc_marked()) {
296          obj->init_mark();
297        } else {
298          assert(hr->is_empty(), "Should have been cleared in phase 2.");
299        }
300      }
301      hr->reset_during_compaction();
302    } else if (!hr->is_pinned()) {
303      hr->compact();
304    }
305    return false;
306  }
307};
308
309void G1MarkSweep::mark_sweep_phase4() {
310  // All pointers are now adjusted, move objects accordingly
311
312  // The ValidateMarkSweep live oops tracking expects us to traverse spaces
313  // in the same order in phase2, phase3 and phase4. We don't quite do that
314  // here (code and comment not fixed for perm removal), so we tell the validate code
315  // to use a higher index (saved from phase2) when verifying perm_gen.
316  G1CollectedHeap* g1h = G1CollectedHeap::heap();
317
318  GCTraceTime(Info, gc, phases) tm("Phase 4: Move objects", gc_timer());
319
320  G1SpaceCompactClosure blk;
321  g1h->heap_region_iterate(&blk);
322
323}
324
325void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) {
326  G1CollectedHeap* g1h = G1CollectedHeap::heap();
327  g1h->heap_region_iterate(blk);
328  blk->update_sets();
329}
330
331void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) {
332  HeapWord* end = hr->end();
333  FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
334
335  hr->set_containing_set(NULL);
336  _humongous_regions_removed++;
337
338  _g1h->free_humongous_region(hr, &dummy_free_list, false /* skip_remset */);
339  prepare_for_compaction(hr, end);
340  dummy_free_list.remove_all();
341}
342
343void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) {
344  // If this is the first live region that we came across which we can compact,
345  // initialize the CompactPoint.
346  if (!is_cp_initialized()) {
347    _cp.space = hr;
348    _cp.threshold = hr->initialize_threshold();
349  }
350  prepare_for_compaction_work(&_cp, hr, end);
351}
352
353void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp,
354                                                          HeapRegion* hr,
355                                                          HeapWord* end) {
356  hr->prepare_for_compaction(cp);
357  // Also clear the part of the card table that will be unused after
358  // compaction.
359  _mrbs->clear(MemRegion(hr->compaction_top(), end));
360}
361
362void G1PrepareCompactClosure::update_sets() {
363  // We'll recalculate total used bytes and recreate the free list
364  // at the end of the GC, so no point in updating those values here.
365  _g1h->remove_from_old_sets(0, _humongous_regions_removed);
366}
367
368bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) {
369  if (hr->is_humongous()) {
370    oop obj = oop(hr->humongous_start_region()->bottom());
371    if (hr->is_starts_humongous() && obj->is_gc_marked()) {
372      obj->forward_to(obj);
373    }
374    if (!obj->is_gc_marked()) {
375      free_humongous_region(hr);
376    }
377  } else if (!hr->is_pinned()) {
378    prepare_for_compaction(hr, hr->end());
379  }
380  return false;
381}
382