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
57 class HeapRegion;
58
59 void 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
125 STWGCTimer* G1MarkSweep::gc_timer() {
126 return G1FullGCScope::instance()->timer();
127 }
128
129 SerialOldTracer* G1MarkSweep::gc_tracer() {
130 return G1FullGCScope::instance()->tracer();
131 }
132
133 void G1MarkSweep::allocate_stacks() {
134 GenMarkSweep::_preserved_count_max = 0;
135 GenMarkSweep::_preserved_marks = NULL;
136 GenMarkSweep::_preserved_count = 0;
137 }
138
139 void 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
223 void 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
235 class 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
253 void 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
287 class G1SpaceCompactClosure: public HeapRegionClosure {
288 public:
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
309 void 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
325 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) {
326 G1CollectedHeap* g1h = G1CollectedHeap::heap();
327 g1h->heap_region_iterate(blk);
328 blk->update_sets();
329 }
330
331 void 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
343 void 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
353 void 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
362 void 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
368 bool 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 }