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(), gc_tracer()->gc_id());
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()->gc_id());
152 gc_tracer()->report_gc_reference_stats(stats);
153
154
155 // This is the point where the entire marking should have completed.
156 assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
157
158 // Unload classes and purge the SystemDictionary.
159 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
160
161 // Unload nmethods.
162 CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);
163
164 // Prune dead klasses from subklass/sibling/implementor lists.
165 Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);
166
167 // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.
168 G1CollectedHeap::heap()->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);
169
170 if (VerifyDuringGC) {
171 HandleMark hm; // handle scope
172 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);
173 Universe::heap()->prepare_for_verify();
174 // Note: we can verify only the heap here. When an object is
175 // marked, the previous value of the mark word (including
176 // identity hash values, ages, etc) is preserved, and the mark
177 // word is set to markOop::marked_value - effectively removing
178 // any hash values from the mark word. These hash values are
179 // used when verifying the dictionaries and so removing them
180 // from the mark word can make verification of the dictionaries
181 // fail. At the end of the GC, the original mark word values
182 // (including hash values) are restored to the appropriate
183 // objects.
184 if (!VerifySilently) {
185 gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying ");
186 }
187 Universe::heap()->verify(VerifySilently, VerifyOption_G1UseMarkWord);
188 if (!VerifySilently) {
189 gclog_or_tty->print_cr("]");
190 }
191 }
192
193 gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
194 }
195
196 class G1PrepareCompactClosure: public HeapRegionClosure {
197 G1CollectedHeap* _g1h;
198 ModRefBarrierSet* _mrbs;
199 CompactPoint _cp;
200 HeapRegionSetCount _humongous_regions_removed;
201
202 void free_humongous_region(HeapRegion* hr) {
203 HeapWord* end = hr->end();
204 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
205
206 assert(hr->startsHumongous(),
207 "Only the start of a humongous region should be freed.");
208
209 hr->set_containing_set(NULL);
210 _humongous_regions_removed.increment(1u, hr->capacity());
211
212 _g1h->free_humongous_region(hr, &dummy_free_list, false /* par */);
213 hr->prepare_for_compaction(&_cp);
214 // Also clear the part of the card table that will be unused after
215 // compaction.
216 _mrbs->clear(MemRegion(hr->compaction_top(), end));
217 dummy_free_list.remove_all();
218 }
219
220 public:
221 G1PrepareCompactClosure(CompactibleSpace* cs)
222 : _g1h(G1CollectedHeap::heap()),
223 _mrbs(_g1h->g1_barrier_set()),
224 _cp(NULL, cs, cs->initialize_threshold()),
225 _humongous_regions_removed() { }
226
227 void update_sets() {
228 // We'll recalculate total used bytes and recreate the free list
229 // at the end of the GC, so no point in updating those values here.
230 HeapRegionSetCount empty_set;
231 _g1h->remove_from_old_sets(empty_set, _humongous_regions_removed);
232 }
233
234 bool doHeapRegion(HeapRegion* hr) {
235 if (hr->isHumongous()) {
236 if (hr->startsHumongous()) {
237 oop obj = oop(hr->bottom());
238 if (obj->is_gc_marked()) {
239 obj->forward_to(obj);
240 } else {
241 free_humongous_region(hr);
242 }
243 } else {
244 assert(hr->continuesHumongous(), "Invalid humongous.");
245 }
246 } else {
247 hr->prepare_for_compaction(&_cp);
248 // Also clear the part of the card table that will be unused after
249 // compaction.
250 _mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
251 }
252 return false;
253 }
254 };
255
256 void G1MarkSweep::mark_sweep_phase2() {
257 // Now all live objects are marked, compute the new object addresses.
258
259 // It is not required that we traverse spaces in the same order in
260 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
261 // tracking expects us to do so. See comment under phase4.
262
263 G1CollectedHeap* g1h = G1CollectedHeap::heap();
264
265 GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
266 GenMarkSweep::trace("2");
267
268 // find the first region
269 HeapRegion* r = g1h->region_at(0);
270 CompactibleSpace* sp = r;
271 if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) {
272 sp = r->next_compaction_space();
273 }
274
275 G1PrepareCompactClosure blk(sp);
276 g1h->heap_region_iterate(&blk);
277 blk.update_sets();
278 }
279
280 class G1AdjustPointersClosure: public HeapRegionClosure {
281 public:
282 bool doHeapRegion(HeapRegion* r) {
283 if (r->isHumongous()) {
284 if (r->startsHumongous()) {
285 // We must adjust the pointers on the single H object.
286 oop obj = oop(r->bottom());
287 // point all the oops to the new location
288 obj->adjust_pointers();
289 }
290 } else {
291 // This really ought to be "as_CompactibleSpace"...
292 r->adjust_pointers();
293 }
294 return false;
295 }
296 };
297
298 void G1MarkSweep::mark_sweep_phase3() {
299 G1CollectedHeap* g1h = G1CollectedHeap::heap();
300
301 // Adjust the pointers to reflect the new locations
302 GCTraceTime tm("phase 3", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
303 GenMarkSweep::trace("3");
304
305 SharedHeap* sh = SharedHeap::heap();
306
307 // Need cleared claim bits for the strong roots processing
308 ClassLoaderDataGraph::clear_claimed_marks();
309
310 sh->process_strong_roots(true, // activate StrongRootsScope
311 SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_AllCodeCache,
312 &GenMarkSweep::adjust_pointer_closure,
313 &GenMarkSweep::adjust_klass_closure);
314
315 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
316 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
317
318 // Now adjust pointers in remaining weak roots. (All of which should
319 // have been cleared if they pointed to non-surviving objects.)
320 sh->process_weak_roots(&GenMarkSweep::adjust_pointer_closure);
321
322 if (G1StringDedup::is_enabled()) {
323 G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);
324 }
325
326 GenMarkSweep::adjust_marks();
327
328 G1AdjustPointersClosure blk;
329 g1h->heap_region_iterate(&blk);
330 }
331
332 class G1SpaceCompactClosure: public HeapRegionClosure {
333 public:
334 G1SpaceCompactClosure() {}
335
336 bool doHeapRegion(HeapRegion* hr) {
337 if (hr->isHumongous()) {
338 if (hr->startsHumongous()) {
339 oop obj = oop(hr->bottom());
340 if (obj->is_gc_marked()) {
341 obj->init_mark();
342 } else {
343 assert(hr->is_empty(), "Should have been cleared in phase 2.");
344 }
345 hr->reset_during_compaction();
346 }
347 } else {
348 hr->compact();
349 }
350 return false;
351 }
352 };
353
354 void G1MarkSweep::mark_sweep_phase4() {
355 // All pointers are now adjusted, move objects accordingly
356
357 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
358 // in the same order in phase2, phase3 and phase4. We don't quite do that
359 // here (code and comment not fixed for perm removal), so we tell the validate code
360 // to use a higher index (saved from phase2) when verifying perm_gen.
361 G1CollectedHeap* g1h = G1CollectedHeap::heap();
362
363 GCTraceTime tm("phase 4", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
364 GenMarkSweep::trace("4");
365
366 G1SpaceCompactClosure blk;
367 g1h->heap_region_iterate(&blk);
368
369 }