1 /*
2 * Copyright (c) 2001, 2013, 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_implementation/g1/g1Log.hpp"
33 #include "gc_implementation/g1/g1MarkSweep.hpp"
34 #include "gc_implementation/shared/gcHeapSummary.hpp"
35 #include "gc_implementation/shared/gcTimer.hpp"
36 #include "gc_implementation/shared/gcTrace.hpp"
37 #include "gc_implementation/shared/gcTraceTime.hpp"
38 #include "memory/gcLocker.hpp"
39 #include "memory/genCollectedHeap.hpp"
40 #include "memory/modRefBarrierSet.hpp"
41 #include "memory/referencePolicy.hpp"
42 #include "memory/space.hpp"
43 #include "oops/instanceRefKlass.hpp"
44 #include "oops/oop.inline.hpp"
45 #include "prims/jvmtiExport.hpp"
46 #include "runtime/biasedLocking.hpp"
47 #include "runtime/fprofiler.hpp"
48 #include "runtime/synchronizer.hpp"
49 #include "runtime/thread.hpp"
50 #include "runtime/vmThread.hpp"
51 #include "utilities/copy.hpp"
52 #include "utilities/events.hpp"
53
54 class HeapRegion;
55
56 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
57 bool clear_all_softrefs) {
58 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
59
60 SharedHeap* sh = SharedHeap::heap();
61 #ifdef ASSERT
62 if (sh->collector_policy()->should_clear_all_soft_refs()) {
63 assert(clear_all_softrefs, "Policy should have been checked earler");
64 }
65 #endif
66 // hook up weak ref data so it can be used during Mark-Sweep
67 assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
68 assert(rp != NULL, "should be non-NULL");
69 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition");
70
71 GenMarkSweep::_ref_processor = rp;
72 rp->setup_policy(clear_all_softrefs);
73
74 // When collecting the permanent generation Method*s may be moving,
75 // so we either have to flush all bcp data or convert it into bci.
76 CodeCache::gc_prologue();
77 Threads::gc_prologue();
78
79 bool marked_for_unloading = false;
80
81 allocate_stacks();
82
83 // We should save the marks of the currently locked biased monitors.
84 // The marking doesn't preserve the marks of biased objects.
85 BiasedLocking::preserve_marks();
86
87 mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
88
89 mark_sweep_phase2();
90
91 // Don't add any more derived pointers during phase3
92 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
93
94 mark_sweep_phase3();
95
96 mark_sweep_phase4();
97
98 GenMarkSweep::restore_marks();
99 BiasedLocking::restore_marks();
100 GenMarkSweep::deallocate_stacks();
101
102 // "free at last gc" is calculated from these.
103 // CHF: cheating for now!!!
104 // Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity());
105 // Universe::set_heap_used_at_last_gc(Universe::heap()->used());
106
107 Threads::gc_epilogue();
108 CodeCache::gc_epilogue();
109 JvmtiExport::gc_epilogue();
110
111 // refs processing: clean slate
112 GenMarkSweep::_ref_processor = NULL;
113 }
114
115
116 void G1MarkSweep::allocate_stacks() {
117 GenMarkSweep::_preserved_count_max = 0;
118 GenMarkSweep::_preserved_marks = NULL;
119 GenMarkSweep::_preserved_count = 0;
120 }
121
122 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
123 bool clear_all_softrefs) {
124 // Recursively traverse all live objects and mark them
125 GCTraceTime tm("phase 1", G1Log::fine() && Verbose, true, gc_timer());
126 GenMarkSweep::trace(" 1");
127
128 SharedHeap* sh = SharedHeap::heap();
129
130 // Need cleared claim bits for the strong roots processing
131 ClassLoaderDataGraph::clear_claimed_marks();
132
133 sh->process_strong_roots(true, // activate StrongRootsScope
134 SharedHeap::SO_SystemClasses,
135 &GenMarkSweep::follow_root_closure,
136 &GenMarkSweep::follow_klass_closure);
137
138 // Process reference objects found during marking
139 ReferenceProcessor* rp = GenMarkSweep::ref_processor();
140 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Sanity");
141
142 rp->setup_policy(clear_all_softrefs);
143 const ReferenceProcessorStats& stats =
144 rp->process_discovered_references(&GenMarkSweep::is_alive,
145 &GenMarkSweep::keep_alive,
146 &GenMarkSweep::follow_stack_closure,
147 NULL,
148 gc_timer());
149 gc_tracer()->report_gc_reference_stats(stats);
150
151
152 // This is the point where the entire marking should have completed.
153 assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
154
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 // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.
165 G1CollectedHeap::heap()->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);
166
167 if (VerifyDuringGC) {
168 HandleMark hm; // handle scope
169 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);
170 Universe::heap()->prepare_for_verify();
171 // Note: we can verify only the heap here. When an object is
172 // marked, the previous value of the mark word (including
173 // identity hash values, ages, etc) is preserved, and the mark
174 // word is set to markOop::marked_value - effectively removing
175 // any hash values from the mark word. These hash values are
176 // used when verifying the dictionaries and so removing them
177 // from the mark word can make verification of the dictionaries
178 // fail. At the end of the GC, the original mark word values
179 // (including hash values) are restored to the appropriate
180 // objects.
181 if (!VerifySilently) {
182 gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying ");
183 }
184 Universe::heap()->verify(VerifySilently, VerifyOption_G1UseMarkWord);
185 if (!VerifySilently) {
186 gclog_or_tty->print_cr("]");
187 }
188 }
189
190 gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
191 }
192
193 class G1PrepareCompactClosure: public HeapRegionClosure {
194 G1CollectedHeap* _g1h;
195 ModRefBarrierSet* _mrbs;
196 CompactPoint _cp;
197 HeapRegionSetCount _humongous_regions_removed;
198
199 void free_humongous_region(HeapRegion* hr) {
200 HeapWord* end = hr->end();
201 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
202
203 assert(hr->startsHumongous(),
204 "Only the start of a humongous region should be freed.");
205
206 hr->set_containing_set(NULL);
207 _humongous_regions_removed.increment(1u, hr->capacity());
208
209 _g1h->free_humongous_region(hr, &dummy_free_list, false /* par */);
210 hr->prepare_for_compaction(&_cp);
211 // Also clear the part of the card table that will be unused after
212 // compaction.
213 _mrbs->clear(MemRegion(hr->compaction_top(), end));
214 dummy_free_list.remove_all();
215 }
216
217 public:
218 G1PrepareCompactClosure(CompactibleSpace* cs)
219 : _g1h(G1CollectedHeap::heap()),
220 _mrbs(_g1h->g1_barrier_set()),
221 _cp(NULL, cs, cs->initialize_threshold()),
222 _humongous_regions_removed() { }
223
224 void update_sets() {
225 // We'll recalculate total used bytes and recreate the free list
226 // at the end of the GC, so no point in updating those values here.
227 HeapRegionSetCount empty_set;
228 _g1h->remove_from_old_sets(empty_set, _humongous_regions_removed);
229 }
230
231 bool doHeapRegion(HeapRegion* hr) {
232 if (hr->isHumongous()) {
233 if (hr->startsHumongous()) {
234 oop obj = oop(hr->bottom());
235 if (obj->is_gc_marked()) {
236 obj->forward_to(obj);
237 } else {
238 free_humongous_region(hr);
239 }
240 } else {
241 assert(hr->continuesHumongous(), "Invalid humongous.");
242 }
243 } else {
244 hr->prepare_for_compaction(&_cp);
245 // Also clear the part of the card table that will be unused after
246 // compaction.
247 _mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
248 }
249 return false;
250 }
251 };
252
253 void G1MarkSweep::mark_sweep_phase2() {
254 // Now all live objects are marked, compute the new object addresses.
255
256 // It is not required that we traverse spaces in the same order in
257 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
258 // tracking expects us to do so. See comment under phase4.
259
260 G1CollectedHeap* g1h = G1CollectedHeap::heap();
261
262 GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer());
263 GenMarkSweep::trace("2");
264
265 // find the first region
266 HeapRegion* r = g1h->region_at(0);
267 CompactibleSpace* sp = r;
268 if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) {
269 sp = r->next_compaction_space();
270 }
271
272 G1PrepareCompactClosure blk(sp);
273 g1h->heap_region_iterate(&blk);
274 blk.update_sets();
275 }
276
277 class G1AdjustPointersClosure: public HeapRegionClosure {
278 public:
279 bool doHeapRegion(HeapRegion* r) {
280 if (r->isHumongous()) {
281 if (r->startsHumongous()) {
282 // We must adjust the pointers on the single H object.
283 oop obj = oop(r->bottom());
284 // point all the oops to the new location
285 obj->adjust_pointers();
286 }
287 } else {
288 // This really ought to be "as_CompactibleSpace"...
289 r->adjust_pointers();
290 }
291 return false;
292 }
293 };
294
295 void G1MarkSweep::mark_sweep_phase3() {
296 G1CollectedHeap* g1h = G1CollectedHeap::heap();
297
298 // Adjust the pointers to reflect the new locations
299 GCTraceTime tm("phase 3", G1Log::fine() && Verbose, true, gc_timer());
300 GenMarkSweep::trace("3");
301
302 SharedHeap* sh = SharedHeap::heap();
303
304 // Need cleared claim bits for the strong roots processing
305 ClassLoaderDataGraph::clear_claimed_marks();
306
307 sh->process_strong_roots(true, // activate StrongRootsScope
308 SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_AllCodeCache,
309 &GenMarkSweep::adjust_pointer_closure,
310 &GenMarkSweep::adjust_klass_closure);
311
312 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
313 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
314
315 // Now adjust pointers in remaining weak roots. (All of which should
316 // have been cleared if they pointed to non-surviving objects.)
317 sh->process_weak_roots(&GenMarkSweep::adjust_pointer_closure);
318
319 GenMarkSweep::adjust_marks();
320
321 G1AdjustPointersClosure blk;
322 g1h->heap_region_iterate(&blk);
323 }
324
325 class G1SpaceCompactClosure: public HeapRegionClosure {
326 public:
327 G1SpaceCompactClosure() {}
328
329 bool doHeapRegion(HeapRegion* hr) {
330 if (hr->isHumongous()) {
331 if (hr->startsHumongous()) {
332 oop obj = oop(hr->bottom());
333 if (obj->is_gc_marked()) {
334 obj->init_mark();
335 } else {
336 assert(hr->is_empty(), "Should have been cleared in phase 2.");
337 }
338 hr->reset_during_compaction();
339 }
340 } else {
341 hr->compact();
342 }
343 return false;
344 }
345 };
346
347 void G1MarkSweep::mark_sweep_phase4() {
348 // All pointers are now adjusted, move objects accordingly
349
350 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
351 // in the same order in phase2, phase3 and phase4. We don't quite do that
352 // here (code and comment not fixed for perm removal), so we tell the validate code
353 // to use a higher index (saved from phase2) when verifying perm_gen.
354 G1CollectedHeap* g1h = G1CollectedHeap::heap();
355
356 GCTraceTime tm("phase 4", G1Log::fine() && Verbose, true, gc_timer());
357 GenMarkSweep::trace("4");
358
359 G1SpaceCompactClosure blk;
360 g1h->heap_region_iterate(&blk);
361
362 }