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