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/aprofiler.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 false, // not scavenging.
136 SharedHeap::SO_SystemClasses,
137 &GenMarkSweep::follow_root_closure,
138 &GenMarkSweep::follow_code_root_closure,
139 &GenMarkSweep::follow_klass_closure);
140
141 // Process reference objects found during marking
142 ReferenceProcessor* rp = GenMarkSweep::ref_processor();
143 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Sanity");
144
145 rp->setup_policy(clear_all_softrefs);
146 const ReferenceProcessorStats& stats =
147 rp->process_discovered_references(&GenMarkSweep::is_alive,
148 &GenMarkSweep::keep_alive,
149 &GenMarkSweep::follow_stack_closure,
150 NULL,
151 gc_timer());
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 strings.
168 StringTable::unlink(&GenMarkSweep::is_alive);
169
170 // Clean up unreferenced symbols in symbol table.
171 SymbolTable::unlink();
172
173 if (VerifyDuringGC) {
174 HandleMark hm; // handle scope
175 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);
176 Universe::heap()->prepare_for_verify();
177 // Note: we can verify only the heap here. When an object is
178 // marked, the previous value of the mark word (including
179 // identity hash values, ages, etc) is preserved, and the mark
180 // word is set to markOop::marked_value - effectively removing
181 // any hash values from the mark word. These hash values are
182 // used when verifying the dictionaries and so removing them
183 // from the mark word can make verification of the dictionaries
184 // fail. At the end of the GC, the orginal mark word values
185 // (including hash values) are restored to the appropriate
186 // objects.
187 if (!VerifySilently) {
188 gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying ");
189 }
190 Universe::heap()->verify(VerifySilently, VerifyOption_G1UseMarkWord);
191 if (!VerifySilently) {
192 gclog_or_tty->print_cr("]");
193 }
194 }
195
196 gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
197 }
198
199 class G1PrepareCompactClosure: public HeapRegionClosure {
200 G1CollectedHeap* _g1h;
201 ModRefBarrierSet* _mrbs;
202 CompactPoint _cp;
203 HumongousRegionSet _humongous_proxy_set;
204
205 void free_humongous_region(HeapRegion* hr) {
206 HeapWord* end = hr->end();
207 size_t dummy_pre_used;
208 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
209
210 assert(hr->startsHumongous(),
211 "Only the start of a humongous region should be freed.");
212 _g1h->free_humongous_region(hr, &dummy_pre_used, &dummy_free_list,
213 &_humongous_proxy_set, false /* par */);
214 hr->prepare_for_compaction(&_cp);
215 // Also clear the part of the card table that will be unused after
216 // compaction.
217 _mrbs->clear(MemRegion(hr->compaction_top(), end));
218 dummy_free_list.remove_all();
219 }
220
221 public:
222 G1PrepareCompactClosure(CompactibleSpace* cs)
223 : _g1h(G1CollectedHeap::heap()),
224 _mrbs(G1CollectedHeap::heap()->mr_bs()),
225 _cp(NULL, cs, cs->initialize_threshold()),
226 _humongous_proxy_set("G1MarkSweep Humongous Proxy Set") { }
227
228 void update_sets() {
229 // We'll recalculate total used bytes and recreate the free list
230 // at the end of the GC, so no point in updating those values here.
231 _g1h->update_sets_after_freeing_regions(0, /* pre_used */
232 NULL, /* free_list */
233 NULL, /* old_proxy_set */
234 &_humongous_proxy_set,
235 false /* par */);
236 }
237
238 bool doHeapRegion(HeapRegion* hr) {
239 if (hr->isHumongous()) {
240 if (hr->startsHumongous()) {
241 oop obj = oop(hr->bottom());
242 if (obj->is_gc_marked()) {
243 obj->forward_to(obj);
244 } else {
245 free_humongous_region(hr);
246 }
247 } else {
248 assert(hr->continuesHumongous(), "Invalid humongous.");
249 }
250 } else {
251 hr->prepare_for_compaction(&_cp);
252 // Also clear the part of the card table that will be unused after
253 // compaction.
254 _mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
255 }
256 return false;
257 }
258 };
259
260 void G1MarkSweep::mark_sweep_phase2() {
261 // Now all live objects are marked, compute the new object addresses.
262
263 // It is not required that we traverse spaces in the same order in
264 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
265 // tracking expects us to do so. See comment under phase4.
266
267 G1CollectedHeap* g1h = G1CollectedHeap::heap();
268
269 GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer());
270 GenMarkSweep::trace("2");
271
272 // find the first region
273 HeapRegion* r = g1h->region_at(0);
274 CompactibleSpace* sp = r;
275 if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) {
276 sp = r->next_compaction_space();
277 }
278
279 G1PrepareCompactClosure blk(sp);
280 g1h->heap_region_iterate(&blk);
281 blk.update_sets();
282 }
283
284 class G1AdjustPointersClosure: public HeapRegionClosure {
285 public:
286 bool doHeapRegion(HeapRegion* r) {
287 if (r->isHumongous()) {
288 if (r->startsHumongous()) {
289 // We must adjust the pointers on the single H object.
290 oop obj = oop(r->bottom());
291 // point all the oops to the new location
292 obj->adjust_pointers();
293 }
294 } else {
295 // This really ought to be "as_CompactibleSpace"...
296 r->adjust_pointers();
297 }
298 return false;
299 }
300 };
301
302 void G1MarkSweep::mark_sweep_phase3() {
303 G1CollectedHeap* g1h = G1CollectedHeap::heap();
304
305 // Adjust the pointers to reflect the new locations
306 GCTraceTime tm("phase 3", G1Log::fine() && Verbose, true, gc_timer());
307 GenMarkSweep::trace("3");
308
309 SharedHeap* sh = SharedHeap::heap();
310
311 // Need cleared claim bits for the strong roots processing
312 ClassLoaderDataGraph::clear_claimed_marks();
313
314 sh->process_strong_roots(true, // activate StrongRootsScope
315 false, // not scavenging.
316 SharedHeap::SO_AllClasses,
317 &GenMarkSweep::adjust_pointer_closure,
318 NULL, // do not touch code cache here
319 &GenMarkSweep::adjust_klass_closure);
320
321 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
322 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
323
324 // Now adjust pointers in remaining weak roots. (All of which should
325 // have been cleared if they pointed to non-surviving objects.)
326 g1h->g1_process_weak_roots(&GenMarkSweep::adjust_pointer_closure);
327
328 GenMarkSweep::adjust_marks();
329
330 G1AdjustPointersClosure blk;
331 g1h->heap_region_iterate(&blk);
332 }
333
334 class G1SpaceCompactClosure: public HeapRegionClosure {
335 public:
336 G1SpaceCompactClosure() {}
337
338 bool doHeapRegion(HeapRegion* hr) {
339 if (hr->isHumongous()) {
340 if (hr->startsHumongous()) {
341 oop obj = oop(hr->bottom());
342 if (obj->is_gc_marked()) {
343 obj->init_mark();
344 } else {
345 assert(hr->is_empty(), "Should have been cleared in phase 2.");
346 }
347 hr->reset_during_compaction();
348 }
349 } else {
350 hr->compact();
351 }
352 return false;
353 }
354 };
355
356 void G1MarkSweep::mark_sweep_phase4() {
357 // All pointers are now adjusted, move objects accordingly
358
359 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
360 // in the same order in phase2, phase3 and phase4. We don't quite do that
361 // here (code and comment not fixed for perm removal), so we tell the validate code
362 // to use a higher index (saved from phase2) when verifying perm_gen.
363 G1CollectedHeap* g1h = G1CollectedHeap::heap();
364
365 GCTraceTime tm("phase 4", G1Log::fine() && Verbose, true, gc_timer());
366 GenMarkSweep::trace("4");
367
368 G1SpaceCompactClosure blk;
369 g1h->heap_region_iterate(&blk);
370
371 }