1 /*
2 * Copyright (c) 2001, 2015, 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/g1Log.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.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.inline.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
64 #ifdef ASSERT
65 if (G1CollectedHeap::heap()->collector_policy()->should_clear_all_soft_refs()) {
66 assert(clear_all_softrefs, "Policy should have been checked earler");
67 }
68 #endif
69 // hook up weak ref data so it can be used during Mark-Sweep
70 assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
71 assert(rp != NULL, "should be non-NULL");
72 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition");
73
74 GenMarkSweep::_ref_processor = rp;
75 rp->setup_policy(clear_all_softrefs);
76
77 // When collecting the permanent generation Method*s may be moving,
78 // so we either have to flush all bcp data or convert it into bci.
79 CodeCache::gc_prologue();
80
81 bool marked_for_unloading = false;
82
83 allocate_stacks();
84
85 // We should save the marks of the currently locked biased monitors.
86 // The marking doesn't preserve the marks of biased objects.
87 BiasedLocking::preserve_marks();
88
89 mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
90
91 mark_sweep_phase2();
92
93 // Don't add any more derived pointers during phase3
94 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
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::_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 tm("phase 1", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
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 root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure,
132 &GenMarkSweep::follow_cld_closure,
133 &follow_code_closure);
134 }
135
136 // Process reference objects found during marking
137 ReferenceProcessor* rp = GenMarkSweep::ref_processor();
138 assert(rp == g1h->ref_processor_stw(), "Sanity");
139
140 rp->setup_policy(clear_all_softrefs);
141 const ReferenceProcessorStats& stats =
142 rp->process_discovered_references(&GenMarkSweep::is_alive,
143 &GenMarkSweep::keep_alive,
144 &GenMarkSweep::follow_stack_closure,
145 NULL,
146 gc_timer(),
147 gc_tracer()->gc_id());
148 gc_tracer()->report_gc_reference_stats(stats);
149
150
151 // This is the point where the entire marking should have completed.
152 assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
153
154 // Unload classes and purge the SystemDictionary.
155 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
156
157 // Unload nmethods.
158 CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);
159
160 // Prune dead klasses from subklass/sibling/implementor lists.
161 Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);
162
163 // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.
164 g1h->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);
165
166 if (VerifyDuringGC) {
167 HandleMark hm; // handle scope
168 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);
169 g1h->prepare_for_verify();
170 // Note: we can verify only the heap here. When an object is
171 // marked, the previous value of the mark word (including
172 // identity hash values, ages, etc) is preserved, and the mark
173 // word is set to markOop::marked_value - effectively removing
174 // any hash values from the mark word. These hash values are
175 // used when verifying the dictionaries and so removing them
176 // from the mark word can make verification of the dictionaries
177 // fail. At the end of the GC, the original mark word values
178 // (including hash values) are restored to the appropriate
179 // objects.
180 if (!VerifySilently) {
181 gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying ");
182 }
183 g1h->verify(VerifySilently, VerifyOption_G1UseMarkWord);
184 if (!VerifySilently) {
185 gclog_or_tty->print_cr("]");
186 }
187 }
188
189 gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
190 }
191
192
193 void G1MarkSweep::mark_sweep_phase2() {
194 // Now all live objects are marked, compute the new object addresses.
195
196 // It is not required that we traverse spaces in the same order in
197 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
198 // tracking expects us to do so. See comment under phase4.
199
200 GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
201
202 prepare_compaction();
203 }
204
205 class G1AdjustPointersClosure: public HeapRegionClosure {
206 public:
207 bool doHeapRegion(HeapRegion* r) {
208 if (r->is_humongous()) {
209 if (r->is_starts_humongous()) {
210 // We must adjust the pointers on the single H object.
211 oop obj = oop(r->bottom());
212 // point all the oops to the new location
213 MarkSweep::adjust_pointers(obj);
214 }
215 } else {
216 // This really ought to be "as_CompactibleSpace"...
217 r->adjust_pointers();
218 }
219 return false;
220 }
221 };
222
223 class G1AlwaysTrueClosure: public BoolObjectClosure {
224 public:
225 bool do_object_b(oop p) { return true; }
226 };
227 static G1AlwaysTrueClosure always_true;
228
229 void G1MarkSweep::mark_sweep_phase3() {
230 G1CollectedHeap* g1h = G1CollectedHeap::heap();
231
232 // Adjust the pointers to reflect the new locations
233 GCTraceTime tm("phase 3", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
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(&always_true, &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 hr->reset_during_compaction();
277 }
278 } else {
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 tm("phase 4", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
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 assert(hr->is_starts_humongous(),
312 "Only the start of a humongous region should be freed.");
313
314 hr->set_containing_set(NULL);
315 _humongous_regions_removed.increment(1u, hr->capacity());
316
317 _g1h->free_humongous_region(hr, &dummy_free_list, false /* par */);
318 prepare_for_compaction(hr, end);
319 dummy_free_list.remove_all();
320 }
321
322 void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) {
323 // If this is the first live region that we came across which we can compact,
324 // initialize the CompactPoint.
325 if (!is_cp_initialized()) {
326 _cp.space = hr;
327 _cp.threshold = hr->initialize_threshold();
328 }
329 prepare_for_compaction_work(&_cp, hr, end);
330 }
331
332 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp,
333 HeapRegion* hr,
334 HeapWord* end) {
335 hr->prepare_for_compaction(cp);
336 // Also clear the part of the card table that will be unused after
337 // compaction.
338 _mrbs->clear(MemRegion(hr->compaction_top(), end));
339 }
340
341 void G1PrepareCompactClosure::update_sets() {
342 // We'll recalculate total used bytes and recreate the free list
343 // at the end of the GC, so no point in updating those values here.
344 HeapRegionSetCount empty_set;
345 _g1h->remove_from_old_sets(empty_set, _humongous_regions_removed);
346 }
347
348 bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) {
349 if (hr->is_humongous()) {
350 if (hr->is_starts_humongous()) {
351 oop obj = oop(hr->bottom());
352 if (obj->is_gc_marked()) {
353 obj->forward_to(obj);
354 } else {
355 free_humongous_region(hr);
356 }
357 } else {
358 assert(hr->is_continues_humongous(), "Invalid humongous.");
359 }
360 } else {
361 prepare_for_compaction(hr, hr->end());
362 }
363 return false;
364 }