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/fprofiler.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 const ReferenceProcessorStats& stats =
174 rp->process_discovered_references(&GenMarkSweep::is_alive,
175 &GenMarkSweep::keep_alive,
176 &GenMarkSweep::follow_stack_closure,
177 NULL,
178 gc_timer());
179 gc_tracer()->report_gc_reference_stats(stats);
180 }
181
182 // This is the point where the entire marking should have completed.
183 assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
184
185 if (ClassUnloading) {
186 GCTraceTime(Debug, gc, phases) trace("Class Unloading", gc_timer());
187
188 // Unload classes and purge the SystemDictionary.
189 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive, gc_timer());
190
191 g1h->complete_cleaning(&GenMarkSweep::is_alive, purged_class);
192 } else {
193 GCTraceTime(Debug, gc, phases) trace("Cleanup", gc_timer());
194 g1h->partial_cleaning(&GenMarkSweep::is_alive, true, true, G1StringDedup::is_enabled());
195 }
196
197 if (VerifyDuringGC) {
198 HandleMark hm; // handle scope
199 #if defined(COMPILER2) || INCLUDE_JVMCI
200 DerivedPointerTableDeactivate dpt_deact;
201 #endif
202 g1h->prepare_for_verify();
203 // Note: we can verify only the heap here. When an object is
204 // marked, the previous value of the mark word (including
205 // identity hash values, ages, etc) is preserved, and the mark
206 // word is set to markOop::marked_value - effectively removing
207 // any hash values from the mark word. These hash values are
208 // used when verifying the dictionaries and so removing them
209 // from the mark word can make verification of the dictionaries
210 // fail. At the end of the GC, the original mark word values
211 // (including hash values) are restored to the appropriate
212 // objects.
213 GCTraceTime(Info, gc, verify)("During GC (full)");
214 g1h->verify(VerifyOption_G1UseMarkWord);
215 }
216
217 gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
218 }
219
220
221 void G1MarkSweep::mark_sweep_phase2() {
222 // Now all live objects are marked, compute the new object addresses.
223
224 // It is not required that we traverse spaces in the same order in
225 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
226 // tracking expects us to do so. See comment under phase4.
227
228 GCTraceTime(Info, gc, phases) tm("Phase 2: Compute new object addresses", gc_timer());
229
230 prepare_compaction();
231 }
232
233 class G1AdjustPointersClosure: public HeapRegionClosure {
234 public:
235 bool doHeapRegion(HeapRegion* r) {
236 if (r->is_humongous()) {
237 if (r->is_starts_humongous()) {
238 // We must adjust the pointers on the single H object.
239 oop obj = oop(r->bottom());
240 // point all the oops to the new location
241 MarkSweep::adjust_pointers(obj);
242 }
243 } else if (!r->is_pinned()) {
244 // This really ought to be "as_CompactibleSpace"...
245 r->adjust_pointers();
246 }
247 return false;
248 }
249 };
250
251 void G1MarkSweep::mark_sweep_phase3() {
252 G1CollectedHeap* g1h = G1CollectedHeap::heap();
253
254 // Adjust the pointers to reflect the new locations
255 GCTraceTime(Info, gc, phases) tm("Phase 3: Adjust pointers", gc_timer());
256
257 // Need cleared claim bits for the roots processing
258 ClassLoaderDataGraph::clear_claimed_marks();
259
260 CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
261 {
262 G1RootProcessor root_processor(g1h, 1);
263 root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure,
264 &GenMarkSweep::adjust_cld_closure,
265 &adjust_code_closure);
266 }
267
268 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
269 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
270
271 // Now adjust pointers in remaining weak roots. (All of which should
272 // have been cleared if they pointed to non-surviving objects.)
273 JNIHandles::weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
274
275 if (G1StringDedup::is_enabled()) {
276 G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);
277 }
278
279 GenMarkSweep::adjust_marks();
280
281 G1AdjustPointersClosure blk;
282 g1h->heap_region_iterate(&blk);
283 }
284
285 class G1SpaceCompactClosure: public HeapRegionClosure {
286 public:
287 G1SpaceCompactClosure() {}
288
289 bool doHeapRegion(HeapRegion* hr) {
290 if (hr->is_humongous()) {
291 if (hr->is_starts_humongous()) {
292 oop obj = oop(hr->bottom());
293 if (obj->is_gc_marked()) {
294 obj->init_mark();
295 } else {
296 assert(hr->is_empty(), "Should have been cleared in phase 2.");
297 }
298 }
299 hr->reset_during_compaction();
300 } else if (!hr->is_pinned()) {
301 hr->compact();
302 }
303 return false;
304 }
305 };
306
307 void G1MarkSweep::mark_sweep_phase4() {
308 // All pointers are now adjusted, move objects accordingly
309
310 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
311 // in the same order in phase2, phase3 and phase4. We don't quite do that
312 // here (code and comment not fixed for perm removal), so we tell the validate code
313 // to use a higher index (saved from phase2) when verifying perm_gen.
314 G1CollectedHeap* g1h = G1CollectedHeap::heap();
315
316 GCTraceTime(Info, gc, phases) tm("Phase 4: Move objects", gc_timer());
317
318 G1SpaceCompactClosure blk;
319 g1h->heap_region_iterate(&blk);
320
321 }
322
323 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) {
324 G1CollectedHeap* g1h = G1CollectedHeap::heap();
325 g1h->heap_region_iterate(blk);
326 blk->update_sets();
327 }
328
329 void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) {
330 HeapWord* end = hr->end();
331 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
332
333 hr->set_containing_set(NULL);
334 _humongous_regions_removed++;
335
336 _g1h->free_humongous_region(hr, &dummy_free_list, false /* skip_remset */);
337 prepare_for_compaction(hr, end);
338 dummy_free_list.remove_all();
339 }
340
341 void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) {
342 // If this is the first live region that we came across which we can compact,
343 // initialize the CompactPoint.
344 if (!is_cp_initialized()) {
345 _cp.space = hr;
346 _cp.threshold = hr->initialize_threshold();
347 }
348 prepare_for_compaction_work(&_cp, hr, end);
349 }
350
351 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp,
352 HeapRegion* hr,
353 HeapWord* end) {
354 hr->prepare_for_compaction(cp);
355 // Also clear the part of the card table that will be unused after
356 // compaction.
357 _mrbs->clear(MemRegion(hr->compaction_top(), end));
358 }
359
360 void G1PrepareCompactClosure::update_sets() {
361 // We'll recalculate total used bytes and recreate the free list
362 // at the end of the GC, so no point in updating those values here.
363 _g1h->remove_from_old_sets(0, _humongous_regions_removed);
364 }
365
366 bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) {
367 if (hr->is_humongous()) {
368 oop obj = oop(hr->humongous_start_region()->bottom());
369 if (hr->is_starts_humongous() && obj->is_gc_marked()) {
370 obj->forward_to(obj);
371 }
372 if (!obj->is_gc_marked()) {
373 free_humongous_region(hr);
374 }
375 } else if (!hr->is_pinned()) {
376 prepare_for_compaction(hr, hr->end());
377 }
378 return false;
379 }