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/atomic.inline.hpp"
48 #include "runtime/biasedLocking.hpp"
49 #include "runtime/fprofiler.hpp"
50 #include "runtime/synchronizer.hpp"
51 #include "runtime/thread.hpp"
52 #include "runtime/vmThread.hpp"
53 #include "utilities/copy.hpp"
54 #include "utilities/events.hpp"
55
56 class HeapRegion;
57
58 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
59 bool clear_all_softrefs) {
60 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
61
62 SharedHeap* sh = SharedHeap::heap();
63 #ifdef ASSERT
64 if (sh->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::_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 Threads::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 // "free at last gc" is calculated from these.
105 // CHF: cheating for now!!!
106 // Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity());
107 // Universe::set_heap_used_at_last_gc(Universe::heap()->used());
108
109 Threads::gc_epilogue();
110 CodeCache::gc_epilogue();
111 JvmtiExport::gc_epilogue();
112
113 // refs processing: clean slate
114 GenMarkSweep::_ref_processor = NULL;
115 }
116
117
118 void G1MarkSweep::allocate_stacks() {
119 GenMarkSweep::_preserved_count_max = 0;
120 GenMarkSweep::_preserved_marks = NULL;
121 GenMarkSweep::_preserved_count = 0;
122 }
123
124 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
125 bool clear_all_softrefs) {
126 // Recursively traverse all live objects and mark them
127 GCTraceTime tm("phase 1", G1Log::fine() && Verbose, true, gc_timer());
128 GenMarkSweep::trace(" 1");
129
130 SharedHeap* sh = SharedHeap::heap();
131
132 // Need cleared claim bits for the strong roots processing
133 ClassLoaderDataGraph::clear_claimed_marks();
134
135 sh->process_strong_roots(true, // activate StrongRootsScope
136 SharedHeap::SO_SystemClasses,
137 &GenMarkSweep::follow_root_closure,
138 &GenMarkSweep::follow_klass_closure);
139
140 // Process reference objects found during marking
141 ReferenceProcessor* rp = GenMarkSweep::ref_processor();
142 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Sanity");
143
144 rp->setup_policy(clear_all_softrefs);
145 const ReferenceProcessorStats& stats =
146 rp->process_discovered_references(&GenMarkSweep::is_alive,
147 &GenMarkSweep::keep_alive,
148 &GenMarkSweep::follow_stack_closure,
149 NULL,
150 gc_timer());
151 gc_tracer()->report_gc_reference_stats(stats);
152
153
154 // This is the point where the entire marking should have completed.
155 assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
156
157 // Unload classes and purge the SystemDictionary.
158 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
159
160 // Unload nmethods.
161 CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);
162
163 // Prune dead klasses from subklass/sibling/implementor lists.
164 Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);
165
166 // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.
167 G1CollectedHeap::heap()->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);
168
169 if (VerifyDuringGC) {
170 HandleMark hm; // handle scope
171 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);
172 Universe::heap()->prepare_for_verify();
173 // Note: we can verify only the heap here. When an object is
174 // marked, the previous value of the mark word (including
175 // identity hash values, ages, etc) is preserved, and the mark
176 // word is set to markOop::marked_value - effectively removing
177 // any hash values from the mark word. These hash values are
178 // used when verifying the dictionaries and so removing them
179 // from the mark word can make verification of the dictionaries
180 // fail. At the end of the GC, the original mark word values
181 // (including hash values) are restored to the appropriate
182 // objects.
183 if (!VerifySilently) {
184 gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying ");
185 }
186 Universe::heap()->verify(VerifySilently, VerifyOption_G1UseMarkWord);
187 if (!VerifySilently) {
188 gclog_or_tty->print_cr("]");
189 }
190 }
191
192 gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
193 }
194
195 class G1PrepareCompactClosure: public HeapRegionClosure {
196 G1CollectedHeap* _g1h;
197 ModRefBarrierSet* _mrbs;
198 CompactPoint _cp;
199 HeapRegionSetCount _humongous_regions_removed;
200
201 void free_humongous_region(HeapRegion* hr) {
202 HeapWord* end = hr->end();
203 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
204
205 assert(hr->startsHumongous(),
206 "Only the start of a humongous region should be freed.");
207
208 hr->set_containing_set(NULL);
209 _humongous_regions_removed.increment(1u, hr->capacity());
210
211 _g1h->free_humongous_region(hr, &dummy_free_list, false /* par */);
212 hr->prepare_for_compaction(&_cp);
213 // Also clear the part of the card table that will be unused after
214 // compaction.
215 _mrbs->clear(MemRegion(hr->compaction_top(), end));
216 dummy_free_list.remove_all();
217 }
218
219 public:
220 G1PrepareCompactClosure(CompactibleSpace* cs)
221 : _g1h(G1CollectedHeap::heap()),
222 _mrbs(_g1h->g1_barrier_set()),
223 _cp(NULL, cs, cs->initialize_threshold()),
224 _humongous_regions_removed() { }
225
226 void update_sets() {
227 // We'll recalculate total used bytes and recreate the free list
228 // at the end of the GC, so no point in updating those values here.
229 HeapRegionSetCount empty_set;
230 _g1h->remove_from_old_sets(empty_set, _humongous_regions_removed);
231 }
232
233 bool doHeapRegion(HeapRegion* hr) {
234 if (hr->isHumongous()) {
235 if (hr->startsHumongous()) {
236 oop obj = oop(hr->bottom());
237 if (obj->is_gc_marked()) {
238 obj->forward_to(obj);
239 } else {
240 free_humongous_region(hr);
241 }
242 } else {
243 assert(hr->continuesHumongous(), "Invalid humongous.");
244 }
245 } else {
246 hr->prepare_for_compaction(&_cp);
247 // Also clear the part of the card table that will be unused after
248 // compaction.
249 _mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
250 }
251 return false;
252 }
253 };
254
255 void G1MarkSweep::mark_sweep_phase2() {
256 // Now all live objects are marked, compute the new object addresses.
257
258 // It is not required that we traverse spaces in the same order in
259 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
260 // tracking expects us to do so. See comment under phase4.
261
262 G1CollectedHeap* g1h = G1CollectedHeap::heap();
263
264 GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer());
265 GenMarkSweep::trace("2");
266
267 // find the first region
268 HeapRegion* r = g1h->region_at(0);
269 CompactibleSpace* sp = r;
270 if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) {
271 sp = r->next_compaction_space();
272 }
273
274 G1PrepareCompactClosure blk(sp);
275 g1h->heap_region_iterate(&blk);
276 blk.update_sets();
277 }
278
279 class G1AdjustPointersClosure: public HeapRegionClosure {
280 public:
281 bool doHeapRegion(HeapRegion* r) {
282 if (r->isHumongous()) {
283 if (r->startsHumongous()) {
284 // We must adjust the pointers on the single H object.
285 oop obj = oop(r->bottom());
286 // point all the oops to the new location
287 obj->adjust_pointers();
288 }
289 } else {
290 // This really ought to be "as_CompactibleSpace"...
291 r->adjust_pointers();
292 }
293 return false;
294 }
295 };
296
297 void G1MarkSweep::mark_sweep_phase3() {
298 G1CollectedHeap* g1h = G1CollectedHeap::heap();
299
300 // Adjust the pointers to reflect the new locations
301 GCTraceTime tm("phase 3", G1Log::fine() && Verbose, true, gc_timer());
302 GenMarkSweep::trace("3");
303
304 SharedHeap* sh = SharedHeap::heap();
305
306 // Need cleared claim bits for the strong roots processing
307 ClassLoaderDataGraph::clear_claimed_marks();
308
309 sh->process_strong_roots(true, // activate StrongRootsScope
310 SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_AllCodeCache,
311 &GenMarkSweep::adjust_pointer_closure,
312 &GenMarkSweep::adjust_klass_closure);
313
314 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
315 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
316
317 // Now adjust pointers in remaining weak roots. (All of which should
318 // have been cleared if they pointed to non-surviving objects.)
319 sh->process_weak_roots(&GenMarkSweep::adjust_pointer_closure);
320
321 if (G1StringDedup::is_enabled()) {
322 G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);
323 }
324
325 GenMarkSweep::adjust_marks();
326
327 G1AdjustPointersClosure blk;
328 g1h->heap_region_iterate(&blk);
329 }
330
331 class G1SpaceCompactClosure: public HeapRegionClosure {
332 public:
333 G1SpaceCompactClosure() {}
334
335 bool doHeapRegion(HeapRegion* hr) {
336 if (hr->isHumongous()) {
337 if (hr->startsHumongous()) {
338 oop obj = oop(hr->bottom());
339 if (obj->is_gc_marked()) {
340 obj->init_mark();
341 } else {
342 assert(hr->is_empty(), "Should have been cleared in phase 2.");
343 }
344 hr->reset_during_compaction();
345 }
346 } else {
347 hr->compact();
348 }
349 return false;
350 }
351 };
352
353 void G1MarkSweep::mark_sweep_phase4() {
354 // All pointers are now adjusted, move objects accordingly
355
356 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
357 // in the same order in phase2, phase3 and phase4. We don't quite do that
358 // here (code and comment not fixed for perm removal), so we tell the validate code
359 // to use a higher index (saved from phase2) when verifying perm_gen.
360 G1CollectedHeap* g1h = G1CollectedHeap::heap();
361
362 GCTraceTime tm("phase 4", G1Log::fine() && Verbose, true, gc_timer());
363 GenMarkSweep::trace("4");
364
365 G1SpaceCompactClosure blk;
366 g1h->heap_region_iterate(&blk);
367
368 }