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/heapMonitoring.hpp"
52 #include "runtime/synchronizer.hpp"
53 #include "runtime/thread.hpp"
54 #include "runtime/vmThread.hpp"
55 #include "utilities/copy.hpp"
56 #include "utilities/events.hpp"
57
58 class HeapRegion;
59
60 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
61 bool clear_all_softrefs) {
62 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
63 HandleMark hm; // Discard invalid handles created during gc
64
65 #if defined(COMPILER2) || INCLUDE_JVMCI
66 DerivedPointerTable::clear();
67 #endif
68 #ifdef ASSERT
69 if (G1CollectedHeap::heap()->collector_policy()->should_clear_all_soft_refs()) {
70 assert(clear_all_softrefs, "Policy should have been checked earler");
71 }
72 #endif
73 // hook up weak ref data so it can be used during Mark-Sweep
74 assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
75 assert(rp != NULL, "should be non-NULL");
76 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition");
77
78 GenMarkSweep::set_ref_processor(rp);
79 rp->setup_policy(clear_all_softrefs);
80
81 // When collecting the permanent generation Method*s may be moving,
82 // so we either have to flush all bcp data or convert it into bci.
83 CodeCache::gc_prologue();
84
85 bool marked_for_unloading = false;
86
87 allocate_stacks();
88
89 // We should save the marks of the currently locked biased monitors.
90 // The marking doesn't preserve the marks of biased objects.
91 BiasedLocking::preserve_marks();
92
93 // Process roots and do the marking.
94 mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
95
96 // Prepare compaction.
97 mark_sweep_phase2();
98
99 #if defined(COMPILER2) || INCLUDE_JVMCI
100 // Don't add any more derived pointers during phase3
101 DerivedPointerTable::set_active(false);
102 #endif
103
104 // Adjust all pointers.
105 mark_sweep_phase3();
106
107 // Do the actual compaction.
108 mark_sweep_phase4();
109
110 GenMarkSweep::restore_marks();
111 BiasedLocking::restore_marks();
112 GenMarkSweep::deallocate_stacks();
113
114 #if defined(COMPILER2) || INCLUDE_JVMCI
115 // Now update the derived pointers.
116 DerivedPointerTable::update_pointers();
117 #endif
118
119 CodeCache::gc_epilogue();
120 JvmtiExport::gc_epilogue();
121
122 // refs processing: clean slate
123 GenMarkSweep::set_ref_processor(NULL);
124 }
125
126 STWGCTimer* G1MarkSweep::gc_timer() {
127 return G1FullGCScope::instance()->timer();
128 }
129
130 SerialOldTracer* G1MarkSweep::gc_tracer() {
131 return G1FullGCScope::instance()->tracer();
132 }
133
134 void G1MarkSweep::allocate_stacks() {
135 GenMarkSweep::_preserved_count_max = 0;
136 GenMarkSweep::_preserved_marks = NULL;
137 GenMarkSweep::_preserved_count = 0;
138 }
139
140 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
141 bool clear_all_softrefs) {
142 // Recursively traverse all live objects and mark them
143 GCTraceTime(Info, gc, phases) tm("Phase 1: Mark live objects", gc_timer());
144
145 G1CollectedHeap* g1h = G1CollectedHeap::heap();
146
147 // Need cleared claim bits for the roots processing
148 ClassLoaderDataGraph::clear_claimed_marks();
149
150 MarkingCodeBlobClosure follow_code_closure(&GenMarkSweep::follow_root_closure, !CodeBlobToOopClosure::FixRelocations);
151 {
152 G1RootProcessor root_processor(g1h, 1);
153 if (ClassUnloading) {
154 root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure,
155 &GenMarkSweep::follow_cld_closure,
156 &follow_code_closure);
157 } else {
158 root_processor.process_all_roots_no_string_table(
159 &GenMarkSweep::follow_root_closure,
160 &GenMarkSweep::follow_cld_closure,
161 &follow_code_closure);
162 }
163 }
164
165 {
166 GCTraceTime(Debug, gc, phases) trace("Reference Processing", gc_timer());
167
168 // Process reference objects found during marking
169 ReferenceProcessor* rp = GenMarkSweep::ref_processor();
170 assert(rp == g1h->ref_processor_stw(), "Sanity");
171
172 rp->setup_policy(clear_all_softrefs);
173 ReferenceProcessorPhaseTimes pt(gc_timer(), rp->num_q());
174
175 const ReferenceProcessorStats& stats =
176 rp->process_discovered_references(&GenMarkSweep::is_alive,
177 &GenMarkSweep::keep_alive,
178 &GenMarkSweep::follow_stack_closure,
179 NULL,
180 &pt);
181 gc_tracer()->report_gc_reference_stats(stats);
182 pt.print_all_references();
183 }
184
185 // This is the point where the entire marking should have completed.
186 assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
187
188 if (ClassUnloading) {
189 GCTraceTime(Debug, gc, phases) trace("Class Unloading", gc_timer());
190
191 // Unload classes and purge the SystemDictionary.
192 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive, gc_timer());
193
194 g1h->complete_cleaning(&GenMarkSweep::is_alive, purged_class);
195 } else {
196 GCTraceTime(Debug, gc, phases) trace("Cleanup", gc_timer());
197 g1h->partial_cleaning(&GenMarkSweep::is_alive, true, true, G1StringDedup::is_enabled());
198 }
199
200 if (VerifyDuringGC) {
201 HandleMark hm; // handle scope
202 #if defined(COMPILER2) || INCLUDE_JVMCI
203 DerivedPointerTableDeactivate dpt_deact;
204 #endif
205 g1h->prepare_for_verify();
206 // Note: we can verify only the heap here. When an object is
207 // marked, the previous value of the mark word (including
208 // identity hash values, ages, etc) is preserved, and the mark
209 // word is set to markOop::marked_value - effectively removing
210 // any hash values from the mark word. These hash values are
211 // used when verifying the dictionaries and so removing them
212 // from the mark word can make verification of the dictionaries
213 // fail. At the end of the GC, the original mark word values
214 // (including hash values) are restored to the appropriate
215 // objects.
216 GCTraceTime(Info, gc, verify)("During GC (full)");
217 g1h->verify(VerifyOption_G1UseMarkWord);
218 }
219
220 gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
221 }
222
223
224 void G1MarkSweep::mark_sweep_phase2() {
225 // Now all live objects are marked, compute the new object addresses.
226
227 // It is not required that we traverse spaces in the same order in
228 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
229 // tracking expects us to do so. See comment under phase4.
230
231 GCTraceTime(Info, gc, phases) tm("Phase 2: Compute new object addresses", gc_timer());
232
233 prepare_compaction();
234 }
235
236 class G1AdjustPointersClosure: public HeapRegionClosure {
237 public:
238 bool doHeapRegion(HeapRegion* r) {
239 if (r->is_humongous()) {
240 if (r->is_starts_humongous()) {
241 // We must adjust the pointers on the single H object.
242 oop obj = oop(r->bottom());
243 // point all the oops to the new location
244 MarkSweep::adjust_pointers(obj);
245 }
246 } else if (!r->is_closed_archive()) {
247 // This really ought to be "as_CompactibleSpace"...
248 r->adjust_pointers();
249 }
250 return false;
251 }
252 };
253
254 void G1MarkSweep::mark_sweep_phase3() {
255 G1CollectedHeap* g1h = G1CollectedHeap::heap();
256
257 // Adjust the pointers to reflect the new locations
258 GCTraceTime(Info, gc, phases) tm("Phase 3: Adjust pointers", gc_timer());
259
260 // Need cleared claim bits for the roots processing
261 ClassLoaderDataGraph::clear_claimed_marks();
262
263 CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
264 {
265 G1RootProcessor root_processor(g1h, 1);
266 root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure,
267 &GenMarkSweep::adjust_cld_closure,
268 &adjust_code_closure);
269 }
270
271 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
272 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
273
274 // Now adjust pointers in remaining weak roots. (All of which should
275 // have been cleared if they pointed to non-surviving objects.)
276 JNIHandles::weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
277 HeapMonitoring::weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
278
279 if (G1StringDedup::is_enabled()) {
280 G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);
281 }
282
283 GenMarkSweep::adjust_marks();
284
285 G1AdjustPointersClosure blk;
286 g1h->heap_region_iterate(&blk);
287 }
288
289 class G1SpaceCompactClosure: public HeapRegionClosure {
290 public:
291 G1SpaceCompactClosure() {}
292
293 bool doHeapRegion(HeapRegion* hr) {
294 if (hr->is_humongous()) {
295 if (hr->is_starts_humongous()) {
296 oop obj = oop(hr->bottom());
297 if (obj->is_gc_marked()) {
298 obj->init_mark();
299 } else {
300 assert(hr->is_empty(), "Should have been cleared in phase 2.");
301 }
302 }
303 hr->reset_during_compaction();
304 } else if (!hr->is_pinned()) {
305 hr->compact();
306 }
307 return false;
308 }
309 };
310
311 void G1MarkSweep::mark_sweep_phase4() {
312 // All pointers are now adjusted, move objects accordingly
313
314 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
315 // in the same order in phase2, phase3 and phase4. We don't quite do that
316 // here (code and comment not fixed for perm removal), so we tell the validate code
317 // to use a higher index (saved from phase2) when verifying perm_gen.
318 G1CollectedHeap* g1h = G1CollectedHeap::heap();
319
320 GCTraceTime(Info, gc, phases) tm("Phase 4: Move objects", gc_timer());
321
322 G1SpaceCompactClosure blk;
323 g1h->heap_region_iterate(&blk);
324
325 }
326
327 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) {
328 G1CollectedHeap* g1h = G1CollectedHeap::heap();
329 g1h->heap_region_iterate(blk);
330 blk->update_sets();
331 }
332
333 void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) {
334 HeapWord* end = hr->end();
335 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
336
337 hr->set_containing_set(NULL);
338 _humongous_regions_removed++;
339
340 _g1h->free_humongous_region(hr, &dummy_free_list, false /* skip_remset */);
341 prepare_for_compaction(hr, end);
342 dummy_free_list.remove_all();
343 }
344
345 void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) {
346 // If this is the first live region that we came across which we can compact,
347 // initialize the CompactPoint.
348 if (!is_cp_initialized()) {
349 _cp.space = hr;
350 _cp.threshold = hr->initialize_threshold();
351 }
352 prepare_for_compaction_work(&_cp, hr, end);
353 }
354
355 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp,
356 HeapRegion* hr,
357 HeapWord* end) {
358 hr->prepare_for_compaction(cp);
359 // Also clear the part of the card table that will be unused after
360 // compaction.
361 _mrbs->clear(MemRegion(hr->compaction_top(), end));
362 }
363
364 void G1PrepareCompactClosure::update_sets() {
365 // We'll recalculate total used bytes and recreate the free list
366 // at the end of the GC, so no point in updating those values here.
367 _g1h->remove_from_old_sets(0, _humongous_regions_removed);
368 }
369
370 bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) {
371 if (hr->is_humongous()) {
372 oop obj = oop(hr->humongous_start_region()->bottom());
373 if (hr->is_starts_humongous() && obj->is_gc_marked()) {
374 obj->forward_to(obj);
375 }
376 if (!obj->is_gc_marked()) {
377 free_humongous_region(hr);
378 }
379 } else if (!hr->is_pinned()) {
380 prepare_for_compaction(hr, hr->end());
381 }
382 return false;
383 }