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 false, // not scavenging.
135 SharedHeap::SO_SystemClasses,
136 &GenMarkSweep::follow_root_closure,
137 &GenMarkSweep::follow_code_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 strings.
167 StringTable::unlink(&GenMarkSweep::is_alive);
168
169 // Clean up unreferenced symbols in symbol table.
170 SymbolTable::unlink();
171
172 if (VerifyDuringGC) {
173 HandleMark hm; // handle scope
174 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);
175 Universe::heap()->prepare_for_verify();
176 // Note: we can verify only the heap here. When an object is
177 // marked, the previous value of the mark word (including
178 // identity hash values, ages, etc) is preserved, and the mark
179 // word is set to markOop::marked_value - effectively removing
180 // any hash values from the mark word. These hash values are
181 // used when verifying the dictionaries and so removing them
182 // from the mark word can make verification of the dictionaries
183 // fail. At the end of the GC, the original mark word values
184 // (including hash values) are restored to the appropriate
185 // objects.
186 if (!VerifySilently) {
187 gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying ");
188 }
189 Universe::heap()->verify(VerifySilently, VerifyOption_G1UseMarkWord);
190 if (!VerifySilently) {
191 gclog_or_tty->print_cr("]");
192 }
193 }
194
195 gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
196 }
197
198 class G1PrepareCompactClosure: public HeapRegionClosure {
199 G1CollectedHeap* _g1h;
200 ModRefBarrierSet* _mrbs;
201 CompactPoint _cp;
202 HumongousRegionSet _humongous_proxy_set;
203
204 void free_humongous_region(HeapRegion* hr) {
205 HeapWord* end = hr->end();
206 size_t dummy_pre_used;
207 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
208
209 assert(hr->startsHumongous(),
210 "Only the start of a humongous region should be freed.");
211 _g1h->free_humongous_region(hr, &dummy_pre_used, &dummy_free_list,
212 &_humongous_proxy_set, 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_proxy_set("G1MarkSweep Humongous Proxy Set") { }
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 _g1h->update_sets_after_freeing_regions(0, /* pre_used */
231 NULL, /* free_list */
232 NULL, /* old_proxy_set */
233 &_humongous_proxy_set,
234 false /* par */);
235 }
236
237 bool doHeapRegion(HeapRegion* hr) {
238 if (hr->isHumongous()) {
239 if (hr->startsHumongous()) {
240 oop obj = oop(hr->bottom());
241 if (obj->is_gc_marked()) {
242 obj->forward_to(obj);
243 } else {
244 free_humongous_region(hr);
245 }
246 } else {
247 assert(hr->continuesHumongous(), "Invalid humongous.");
248 }
249 } else {
250 hr->prepare_for_compaction(&_cp);
251 // Also clear the part of the card table that will be unused after
252 // compaction.
253 _mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
254 }
255 return false;
256 }
257 };
258
259 void G1MarkSweep::mark_sweep_phase2() {
260 // Now all live objects are marked, compute the new object addresses.
261
262 // It is not required that we traverse spaces in the same order in
263 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
264 // tracking expects us to do so. See comment under phase4.
265
266 G1CollectedHeap* g1h = G1CollectedHeap::heap();
267
268 GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer());
269 GenMarkSweep::trace("2");
270
271 // find the first region
272 HeapRegion* r = g1h->region_at(0);
273 CompactibleSpace* sp = r;
274 if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) {
275 sp = r->next_compaction_space();
276 }
277
278 G1PrepareCompactClosure blk(sp);
279 g1h->heap_region_iterate(&blk);
280 blk.update_sets();
281 }
282
283 class G1AdjustPointersClosure: public HeapRegionClosure {
284 public:
285 bool doHeapRegion(HeapRegion* r) {
286 if (r->isHumongous()) {
287 if (r->startsHumongous()) {
288 // We must adjust the pointers on the single H object.
289 oop obj = oop(r->bottom());
290 // point all the oops to the new location
291 obj->adjust_pointers();
292 }
293 } else {
294 // This really ought to be "as_CompactibleSpace"...
295 r->adjust_pointers();
296 }
297 return false;
298 }
299 };
300
301 void G1MarkSweep::mark_sweep_phase3() {
302 G1CollectedHeap* g1h = G1CollectedHeap::heap();
303
304 // Adjust the pointers to reflect the new locations
305 GCTraceTime tm("phase 3", G1Log::fine() && Verbose, true, gc_timer());
306 GenMarkSweep::trace("3");
307
308 SharedHeap* sh = SharedHeap::heap();
309
310 // Need cleared claim bits for the strong roots processing
311 ClassLoaderDataGraph::clear_claimed_marks();
312
313 sh->process_strong_roots(true, // activate StrongRootsScope
314 false, // not scavenging.
315 SharedHeap::SO_AllClasses,
316 &GenMarkSweep::adjust_pointer_closure,
317 NULL, // do not touch code cache here
318 &GenMarkSweep::adjust_klass_closure);
319
320 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
321 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
322
323 // Now adjust pointers in remaining weak roots. (All of which should
324 // have been cleared if they pointed to non-surviving objects.)
325 g1h->g1_process_weak_roots(&GenMarkSweep::adjust_pointer_closure);
326
327 GenMarkSweep::adjust_marks();
328
329 G1AdjustPointersClosure blk;
330 g1h->heap_region_iterate(&blk);
331 }
332
333 class G1SpaceCompactClosure: public HeapRegionClosure {
334 public:
335 G1SpaceCompactClosure() {}
336
337 bool doHeapRegion(HeapRegion* hr) {
338 if (hr->isHumongous()) {
339 if (hr->startsHumongous()) {
340 oop obj = oop(hr->bottom());
341 if (obj->is_gc_marked()) {
342 obj->init_mark();
343 } else {
344 assert(hr->is_empty(), "Should have been cleared in phase 2.");
345 }
346 hr->reset_during_compaction();
347 }
348 } else {
349 hr->compact();
350 }
351 return false;
352 }
353 };
354
355 void G1MarkSweep::mark_sweep_phase4() {
356 // All pointers are now adjusted, move objects accordingly
357
358 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
359 // in the same order in phase2, phase3 and phase4. We don't quite do that
360 // here (code and comment not fixed for perm removal), so we tell the validate code
361 // to use a higher index (saved from phase2) when verifying perm_gen.
362 G1CollectedHeap* g1h = G1CollectedHeap::heap();
363
364 GCTraceTime tm("phase 4", G1Log::fine() && Verbose, true, gc_timer());
365 GenMarkSweep::trace("4");
366
367 G1SpaceCompactClosure blk;
368 g1h->heap_region_iterate(&blk);
369
370 }