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