1 /*
2 * Copyright (c) 2001, 2014, 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/g1/g1StringDedup.hpp"
35 #include "gc_implementation/shared/gcHeapSummary.hpp"
36 #include "gc_implementation/shared/gcTimer.hpp"
37 #include "gc_implementation/shared/gcTrace.hpp"
38 #include "gc_implementation/shared/gcTraceTime.hpp"
39 #include "memory/gcLocker.hpp"
40 #include "memory/genCollectedHeap.hpp"
41 #include "memory/modRefBarrierSet.hpp"
42 #include "memory/referencePolicy.hpp"
43 #include "memory/space.hpp"
44 #include "oops/instanceRefKlass.hpp"
45 #include "oops/oop.inline.hpp"
46 #include "prims/jvmtiExport.hpp"
47 #include "runtime/biasedLocking.hpp"
48 #include "runtime/fprofiler.hpp"
49 #include "runtime/synchronizer.hpp"
50 #include "runtime/thread.hpp"
51 #include "runtime/vmThread.hpp"
52 #include "utilities/copy.hpp"
53 #include "utilities/events.hpp"
54
55 class HeapRegion;
56
57 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
58 bool clear_all_softrefs) {
59 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
60
61 SharedHeap* sh = SharedHeap::heap();
62 #ifdef ASSERT
63 if (sh->collector_policy()->should_clear_all_soft_refs()) {
64 assert(clear_all_softrefs, "Policy should have been checked earler");
65 }
66 #endif
67 // hook up weak ref data so it can be used during Mark-Sweep
68 assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
69 assert(rp != NULL, "should be non-NULL");
70 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition");
71
72 GenMarkSweep::_ref_processor = rp;
73 rp->setup_policy(clear_all_softrefs);
74
75 // When collecting the permanent generation Method*s may be moving,
76 // so we either have to flush all bcp data or convert it into bci.
77 CodeCache::gc_prologue();
78 Threads::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 // Don't add any more derived pointers during phase3
93 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
94
95 mark_sweep_phase3();
96
97 mark_sweep_phase4();
98
99 GenMarkSweep::restore_marks();
100 BiasedLocking::restore_marks();
101 GenMarkSweep::deallocate_stacks();
102
103 // "free at last gc" is calculated from these.
104 // CHF: cheating for now!!!
105 // Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity());
106 // Universe::set_heap_used_at_last_gc(Universe::heap()->used());
107
108 Threads::gc_epilogue();
109 CodeCache::gc_epilogue();
110 JvmtiExport::gc_epilogue();
111
112 // refs processing: clean slate
113 GenMarkSweep::_ref_processor = NULL;
114 }
115
116
117 void G1MarkSweep::allocate_stacks() {
118 GenMarkSweep::_preserved_count_max = 0;
119 GenMarkSweep::_preserved_marks = NULL;
120 GenMarkSweep::_preserved_count = 0;
121 }
122
123 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
124 bool clear_all_softrefs) {
125 // Recursively traverse all live objects and mark them
126 GCTraceTime tm("phase 1", G1Log::fine() && Verbose, true, gc_timer());
127 GenMarkSweep::trace(" 1");
128
129 SharedHeap* sh = SharedHeap::heap();
130
131 // Need cleared claim bits for the strong roots processing
132 ClassLoaderDataGraph::clear_claimed_marks();
133
134 sh->process_strong_roots(true, // activate StrongRootsScope
135 SharedHeap::SO_SystemClasses,
136 &GenMarkSweep::follow_root_closure,
137 &GenMarkSweep::follow_klass_closure);
138
139 // Process reference objects found during marking
140 ReferenceProcessor* rp = GenMarkSweep::ref_processor();
141 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Sanity");
142
143 rp->setup_policy(clear_all_softrefs);
144 const ReferenceProcessorStats& stats =
145 rp->process_discovered_references(&GenMarkSweep::is_alive,
146 &GenMarkSweep::keep_alive,
147 &GenMarkSweep::follow_stack_closure,
148 NULL,
149 gc_timer());
150 gc_tracer()->report_gc_reference_stats(stats);
151
152
153 // This is the point where the entire marking should have completed.
154 assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
155
156 // Unload classes and purge the SystemDictionary.
157 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
158
159 // Unload nmethods.
160 CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);
161
162 // Prune dead klasses from subklass/sibling/implementor lists.
163 Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);
164
165 // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.
166 G1CollectedHeap::heap()->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);
167
168 if (VerifyDuringGC) {
169 HandleMark hm; // handle scope
170 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);
171 Universe::heap()->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 Universe::heap()->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 class G1PrepareCompactClosure: public HeapRegionClosure {
195 G1CollectedHeap* _g1h;
196 ModRefBarrierSet* _mrbs;
197 CompactPoint _cp;
198 HeapRegionSetCount _humongous_regions_removed;
199
200 void free_humongous_region(HeapRegion* hr) {
201 HeapWord* end = hr->end();
202 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
203
204 assert(hr->startsHumongous(),
205 "Only the start of a humongous region should be freed.");
206
207 hr->set_containing_set(NULL);
208 _humongous_regions_removed.increment(1u, hr->capacity());
209
210 _g1h->free_humongous_region(hr, &dummy_free_list, false /* par */);
211 hr->prepare_for_compaction(&_cp);
212 // Also clear the part of the card table that will be unused after
213 // compaction.
214 _mrbs->clear(MemRegion(hr->compaction_top(), end));
215 dummy_free_list.remove_all();
216 }
217
218 public:
219 G1PrepareCompactClosure(CompactibleSpace* cs)
220 : _g1h(G1CollectedHeap::heap()),
221 _mrbs(_g1h->g1_barrier_set()),
222 _cp(NULL, cs, cs->initialize_threshold()),
223 _humongous_regions_removed() { }
224
225 void update_sets() {
226 // We'll recalculate total used bytes and recreate the free list
227 // at the end of the GC, so no point in updating those values here.
228 HeapRegionSetCount empty_set;
229 _g1h->remove_from_old_sets(empty_set, _humongous_regions_removed);
230 }
231
232 bool doHeapRegion(HeapRegion* hr) {
233 if (hr->isHumongous()) {
234 if (hr->startsHumongous()) {
235 oop obj = oop(hr->bottom());
236 if (obj->is_gc_marked()) {
237 obj->forward_to(obj);
238 } else {
239 free_humongous_region(hr);
240 }
241 } else {
242 assert(hr->continuesHumongous(), "Invalid humongous.");
243 }
244 } else {
245 hr->prepare_for_compaction(&_cp);
246 // Also clear the part of the card table that will be unused after
247 // compaction.
248 _mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
249 }
250 return false;
251 }
252 };
253
254 void G1MarkSweep::mark_sweep_phase2() {
255 // Now all live objects are marked, compute the new object addresses.
256
257 // It is not required that we traverse spaces in the same order in
258 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
259 // tracking expects us to do so. See comment under phase4.
260
261 G1CollectedHeap* g1h = G1CollectedHeap::heap();
262
263 GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer());
264 GenMarkSweep::trace("2");
265
266 // find the first region
267 HeapRegion* r = g1h->region_at(0);
268 CompactibleSpace* sp = r;
269 if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) {
270 sp = r->next_compaction_space();
271 }
272
273 G1PrepareCompactClosure blk(sp);
274 g1h->heap_region_iterate(&blk);
275 blk.update_sets();
276 }
277
278 class G1AdjustPointersClosure: public HeapRegionClosure {
279 public:
280 bool doHeapRegion(HeapRegion* r) {
281 if (r->isHumongous()) {
282 if (r->startsHumongous()) {
283 // We must adjust the pointers on the single H object.
284 oop obj = oop(r->bottom());
285 // point all the oops to the new location
286 obj->adjust_pointers();
287 }
288 } else {
289 // This really ought to be "as_CompactibleSpace"...
290 r->adjust_pointers();
291 }
292 return false;
293 }
294 };
295
296 void G1MarkSweep::mark_sweep_phase3() {
297 G1CollectedHeap* g1h = G1CollectedHeap::heap();
298
299 // Adjust the pointers to reflect the new locations
300 GCTraceTime tm("phase 3", G1Log::fine() && Verbose, true, gc_timer());
301 GenMarkSweep::trace("3");
302
303 SharedHeap* sh = SharedHeap::heap();
304
305 // Need cleared claim bits for the strong roots processing
306 ClassLoaderDataGraph::clear_claimed_marks();
307
308 sh->process_strong_roots(true, // activate StrongRootsScope
309 SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_AllCodeCache,
310 &GenMarkSweep::adjust_pointer_closure,
311 &GenMarkSweep::adjust_klass_closure);
312
313 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
314 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
315
316 // Now adjust pointers in remaining weak roots. (All of which should
317 // have been cleared if they pointed to non-surviving objects.)
318 sh->process_weak_roots(&GenMarkSweep::adjust_pointer_closure);
319
320 if (G1StringDedup::is_enabled()) {
321 G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);
322 }
323
324 GenMarkSweep::adjust_marks();
325
326 G1AdjustPointersClosure blk;
327 g1h->heap_region_iterate(&blk);
328 }
329
330 class G1SpaceCompactClosure: public HeapRegionClosure {
331 public:
332 G1SpaceCompactClosure() {}
333
334 bool doHeapRegion(HeapRegion* hr) {
335 if (hr->isHumongous()) {
336 if (hr->startsHumongous()) {
337 oop obj = oop(hr->bottom());
338 if (obj->is_gc_marked()) {
339 obj->init_mark();
340 } else {
341 assert(hr->is_empty(), "Should have been cleared in phase 2.");
342 }
343 hr->reset_during_compaction();
344 }
345 } else {
346 hr->compact();
347 }
348 return false;
349 }
350 };
351
352 void G1MarkSweep::mark_sweep_phase4() {
353 // All pointers are now adjusted, move objects accordingly
354
355 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
356 // in the same order in phase2, phase3 and phase4. We don't quite do that
357 // here (code and comment not fixed for perm removal), so we tell the validate code
358 // to use a higher index (saved from phase2) when verifying perm_gen.
359 G1CollectedHeap* g1h = G1CollectedHeap::heap();
360
361 GCTraceTime tm("phase 4", G1Log::fine() && Verbose, true, gc_timer());
362 GenMarkSweep::trace("4");
363
364 G1SpaceCompactClosure blk;
365 g1h->heap_region_iterate(&blk);
366
367 }