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 if (ClassUnloading) {
155 // Unload classes and purge the SystemDictionary.
156 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
157
158 // Unload nmethods.
159 CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);
160
161 // Prune dead klasses from subklass/sibling/implementor lists.
162 Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);
163 }
164
165 // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.
166 g1h->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);
167
168 if (VerifyDuringGC) {
169 HandleMark hm; // handle scope
170 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);
171 g1h->prepare_for_verify();
172 // Note: we can verify only the heap here. When an object is
173 // marked, the previous value of the mark word (including
174 // identity hash values, ages, etc) is preserved, and the mark
175 // word is set to markOop::marked_value - effectively removing
176 // any hash values from the mark word. These hash values are
177 // used when verifying the dictionaries and so removing them
178 // from the mark word can make verification of the dictionaries
179 // fail. At the end of the GC, the original mark word values
180 // (including hash values) are restored to the appropriate
181 // objects.
182 if (!VerifySilently) {
183 gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying ");
184 }
185 g1h->verify(VerifySilently, VerifyOption_G1UseMarkWord);
186 if (!VerifySilently) {
187 gclog_or_tty->print_cr("]");
188 }
189 }
190
191 gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
192 }
193
194
195 void G1MarkSweep::mark_sweep_phase2() {
196 // Now all live objects are marked, compute the new object addresses.
197
198 // It is not required that we traverse spaces in the same order in
199 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
200 // tracking expects us to do so. See comment under phase4.
201
202 GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
203
204 prepare_compaction();
205 }
206
207 class G1AdjustPointersClosure: public HeapRegionClosure {
208 public:
209 bool doHeapRegion(HeapRegion* r) {
210 if (r->is_humongous()) {
211 if (r->is_starts_humongous()) {
212 // We must adjust the pointers on the single H object.
213 oop obj = oop(r->bottom());
214 // point all the oops to the new location
215 MarkSweep::adjust_pointers(obj);
216 }
217 } else {
218 // This really ought to be "as_CompactibleSpace"...
219 r->adjust_pointers();
220 }
221 return false;
222 }
223 };
224
225 class G1AlwaysTrueClosure: public BoolObjectClosure {
226 public:
227 bool do_object_b(oop p) { return true; }
228 };
229 static G1AlwaysTrueClosure always_true;
230
231 void G1MarkSweep::mark_sweep_phase3() {
232 G1CollectedHeap* g1h = G1CollectedHeap::heap();
233
234 // Adjust the pointers to reflect the new locations
235 GCTraceTime tm("phase 3", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
236
237 // Need cleared claim bits for the roots processing
238 ClassLoaderDataGraph::clear_claimed_marks();
239
240 CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
241 {
242 G1RootProcessor root_processor(g1h, 1);
243 root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure,
244 &GenMarkSweep::adjust_cld_closure,
245 &adjust_code_closure);
246 }
247
248 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
249 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
250
251 // Now adjust pointers in remaining weak roots. (All of which should
252 // have been cleared if they pointed to non-surviving objects.)
253 JNIHandles::weak_oops_do(&always_true, &GenMarkSweep::adjust_pointer_closure);
254
255 if (G1StringDedup::is_enabled()) {
256 G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);
257 }
258
259 GenMarkSweep::adjust_marks();
260
261 G1AdjustPointersClosure blk;
262 g1h->heap_region_iterate(&blk);
263 }
264
265 class G1SpaceCompactClosure: public HeapRegionClosure {
266 public:
267 G1SpaceCompactClosure() {}
268
269 bool doHeapRegion(HeapRegion* hr) {
270 if (hr->is_humongous()) {
271 if (hr->is_starts_humongous()) {
272 oop obj = oop(hr->bottom());
273 if (obj->is_gc_marked()) {
274 obj->init_mark();
275 } else {
276 assert(hr->is_empty(), "Should have been cleared in phase 2.");
277 }
278 hr->reset_during_compaction();
279 }
280 } else {
281 hr->compact();
282 }
283 return false;
284 }
285 };
286
287 void G1MarkSweep::mark_sweep_phase4() {
288 // All pointers are now adjusted, move objects accordingly
289
290 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
291 // in the same order in phase2, phase3 and phase4. We don't quite do that
292 // here (code and comment not fixed for perm removal), so we tell the validate code
293 // to use a higher index (saved from phase2) when verifying perm_gen.
294 G1CollectedHeap* g1h = G1CollectedHeap::heap();
295
296 GCTraceTime tm("phase 4", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
297
298 G1SpaceCompactClosure blk;
299 g1h->heap_region_iterate(&blk);
300
301 }
302
303 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) {
304 G1CollectedHeap* g1h = G1CollectedHeap::heap();
305 g1h->heap_region_iterate(blk);
306 blk->update_sets();
307 }
308
309 void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) {
310 HeapWord* end = hr->end();
311 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
312
313 assert(hr->is_starts_humongous(),
314 "Only the start of a humongous region should be freed.");
315
316 hr->set_containing_set(NULL);
317 _humongous_regions_removed.increment(1u, hr->capacity());
318
319 _g1h->free_humongous_region(hr, &dummy_free_list, false /* par */);
320 prepare_for_compaction(hr, end);
321 dummy_free_list.remove_all();
322 }
323
324 void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) {
325 // If this is the first live region that we came across which we can compact,
326 // initialize the CompactPoint.
327 if (!is_cp_initialized()) {
328 _cp.space = hr;
329 _cp.threshold = hr->initialize_threshold();
330 }
331 prepare_for_compaction_work(&_cp, hr, end);
332 }
333
334 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp,
335 HeapRegion* hr,
336 HeapWord* end) {
337 hr->prepare_for_compaction(cp);
338 // Also clear the part of the card table that will be unused after
339 // compaction.
340 _mrbs->clear(MemRegion(hr->compaction_top(), end));
341 }
342
343 void G1PrepareCompactClosure::update_sets() {
344 // We'll recalculate total used bytes and recreate the free list
345 // at the end of the GC, so no point in updating those values here.
346 HeapRegionSetCount empty_set;
347 _g1h->remove_from_old_sets(empty_set, _humongous_regions_removed);
348 }
349
350 bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) {
351 if (hr->is_humongous()) {
352 if (hr->is_starts_humongous()) {
353 oop obj = oop(hr->bottom());
354 if (obj->is_gc_marked()) {
355 obj->forward_to(obj);
356 } else {
357 free_humongous_region(hr);
358 }
359 } else {
360 assert(hr->is_continues_humongous(), "Invalid humongous.");
361 }
362 } else {
363 prepare_for_compaction(hr, hr->end());
364 }
365 return false;
366 }