1 /*
2 * Copyright (c) 2001, 2010, 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/g1MarkSweep.hpp"
33 #include "memory/gcLocker.hpp"
34 #include "memory/genCollectedHeap.hpp"
35 #include "memory/modRefBarrierSet.hpp"
36 #include "memory/referencePolicy.hpp"
37 #include "memory/space.hpp"
38 #include "oops/instanceRefKlass.hpp"
39 #include "oops/oop.inline.hpp"
40 #include "prims/jvmtiExport.hpp"
41 #include "runtime/aprofiler.hpp"
42 #include "runtime/biasedLocking.hpp"
43 #include "runtime/fprofiler.hpp"
44 #include "runtime/synchronizer.hpp"
45 #include "runtime/thread.hpp"
46 #include "runtime/vmThread.hpp"
47 #include "utilities/copy.hpp"
48 #include "utilities/events.hpp"
49
50 class HeapRegion;
51
52 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
53 bool clear_all_softrefs) {
54 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
55
56 SharedHeap* sh = SharedHeap::heap();
57 #ifdef ASSERT
58 if (sh->collector_policy()->should_clear_all_soft_refs()) {
59 assert(clear_all_softrefs, "Policy should have been checked earler");
60 }
61 #endif
62 // hook up weak ref data so it can be used during Mark-Sweep
63 assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
64 assert(rp != NULL, "should be non-NULL");
65 GenMarkSweep::_ref_processor = rp;
66 rp->setup_policy(clear_all_softrefs);
67
68 // When collecting the permanent generation methodOops may be moving,
69 // so we either have to flush all bcp data or convert it into bci.
70 CodeCache::gc_prologue();
71 Threads::gc_prologue();
72
73 // Increment the invocation count for the permanent generation, since it is
74 // implicitly collected whenever we do a full mark sweep collection.
75 sh->perm_gen()->stat_record()->invocations++;
76
77 bool marked_for_unloading = false;
78
79 allocate_stacks();
80
81 // We should save the marks of the currently locked biased monitors.
82 // The marking doesn't preserve the marks of biased objects.
83 BiasedLocking::preserve_marks();
84
85 mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
86
87 if (VerifyDuringGC) {
88 G1CollectedHeap* g1h = G1CollectedHeap::heap();
89 g1h->checkConcurrentMark();
90 }
91
92 mark_sweep_phase2();
93
94 // Don't add any more derived pointers during phase3
95 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
96
97 mark_sweep_phase3();
98
99 mark_sweep_phase4();
100
101 GenMarkSweep::restore_marks();
102 BiasedLocking::restore_marks();
103 GenMarkSweep::deallocate_stacks();
104
105 // We must invalidate the perm-gen rs, so that it gets rebuilt.
106 GenRemSet* rs = sh->rem_set();
107 rs->invalidate(sh->perm_gen()->used_region(), true /*whole_heap*/);
108
109 // "free at last gc" is calculated from these.
110 // CHF: cheating for now!!!
111 // Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity());
112 // Universe::set_heap_used_at_last_gc(Universe::heap()->used());
113
114 Threads::gc_epilogue();
115 CodeCache::gc_epilogue();
116
117 // refs processing: clean slate
118 GenMarkSweep::_ref_processor = NULL;
119 }
120
121
122 void G1MarkSweep::allocate_stacks() {
123 GenMarkSweep::_preserved_count_max = 0;
124 GenMarkSweep::_preserved_marks = NULL;
125 GenMarkSweep::_preserved_count = 0;
126 }
127
128 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
129 bool clear_all_softrefs) {
130 // Recursively traverse all live objects and mark them
131 EventMark m("1 mark object");
132 TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
133 GenMarkSweep::trace(" 1");
134
135 SharedHeap* sh = SharedHeap::heap();
136
137 sh->process_strong_roots(true, // activeate StrongRootsScope
138 true, // Collecting permanent generation.
139 SharedHeap::SO_SystemClasses,
140 &GenMarkSweep::follow_root_closure,
141 &GenMarkSweep::follow_code_root_closure,
142 &GenMarkSweep::follow_root_closure);
143
144 // Process reference objects found during marking
145 ReferenceProcessor* rp = GenMarkSweep::ref_processor();
146 rp->setup_policy(clear_all_softrefs);
147 rp->process_discovered_references(&GenMarkSweep::is_alive,
148 &GenMarkSweep::keep_alive,
149 &GenMarkSweep::follow_stack_closure,
150 NULL);
151
152 // Follow system dictionary roots and unload classes
153 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
154 assert(GenMarkSweep::_marking_stack.is_empty(),
155 "stack should be empty by now");
156
157 // Follow code cache roots (has to be done after system dictionary,
158 // assumes all live klasses are marked)
159 CodeCache::do_unloading(&GenMarkSweep::is_alive,
160 &GenMarkSweep::keep_alive,
161 purged_class);
162 GenMarkSweep::follow_stack();
163
164 // Update subklass/sibling/implementor links of live klasses
165 GenMarkSweep::follow_weak_klass_links();
166 assert(GenMarkSweep::_marking_stack.is_empty(),
167 "stack should be empty by now");
168
169 // Visit memoized MDO's and clear any unmarked weak refs
170 GenMarkSweep::follow_mdo_weak_refs();
171 assert(GenMarkSweep::_marking_stack.is_empty(), "just drained");
172
173
174 // Visit symbol and interned string tables and delete unmarked oops
175 SymbolTable::unlink(&GenMarkSweep::is_alive);
176 StringTable::unlink(&GenMarkSweep::is_alive);
177
178 assert(GenMarkSweep::_marking_stack.is_empty(),
179 "stack should be empty by now");
180 }
181
182 class G1PrepareCompactClosure: public HeapRegionClosure {
183 ModRefBarrierSet* _mrbs;
184 CompactPoint _cp;
185
186 void free_humongous_region(HeapRegion* hr) {
187 HeapWord* bot = hr->bottom();
188 HeapWord* end = hr->end();
189 assert(hr->startsHumongous(),
190 "Only the start of a humongous region should be freed.");
191 G1CollectedHeap::heap()->free_region(hr);
192 hr->prepare_for_compaction(&_cp);
193 // Also clear the part of the card table that will be unused after
194 // compaction.
195 _mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
196 }
197
198 public:
199 G1PrepareCompactClosure(CompactibleSpace* cs) :
200 _cp(NULL, cs, cs->initialize_threshold()),
201 _mrbs(G1CollectedHeap::heap()->mr_bs())
202 {}
203 bool doHeapRegion(HeapRegion* hr) {
204 if (hr->isHumongous()) {
205 if (hr->startsHumongous()) {
206 oop obj = oop(hr->bottom());
207 if (obj->is_gc_marked()) {
208 obj->forward_to(obj);
209 } else {
210 free_humongous_region(hr);
211 }
212 } else {
213 assert(hr->continuesHumongous(), "Invalid humongous.");
214 }
215 } else {
216 hr->prepare_for_compaction(&_cp);
217 // Also clear the part of the card table that will be unused after
218 // compaction.
219 _mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
220 }
221 return false;
222 }
223 };
224
225 // Finds the first HeapRegion.
226 class FindFirstRegionClosure: public HeapRegionClosure {
227 HeapRegion* _a_region;
228 public:
229 FindFirstRegionClosure() : _a_region(NULL) {}
230 bool doHeapRegion(HeapRegion* r) {
231 _a_region = r;
232 return true;
233 }
234 HeapRegion* result() { return _a_region; }
235 };
236
237 void G1MarkSweep::mark_sweep_phase2() {
238 // Now all live objects are marked, compute the new object addresses.
239
240 // It is imperative that we traverse perm_gen LAST. If dead space is
241 // allowed a range of dead object may get overwritten by a dead int
242 // array. If perm_gen is not traversed last a klassOop may get
243 // overwritten. This is fine since it is dead, but if the class has dead
244 // instances we have to skip them, and in order to find their size we
245 // need the klassOop!
246 //
247 // It is not required that we traverse spaces in the same order in
248 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
249 // tracking expects us to do so. See comment under phase4.
250
251 G1CollectedHeap* g1h = G1CollectedHeap::heap();
252 Generation* pg = g1h->perm_gen();
253
254 EventMark m("2 compute new addresses");
255 TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);
256 GenMarkSweep::trace("2");
257
258 FindFirstRegionClosure cl;
259 g1h->heap_region_iterate(&cl);
260 HeapRegion *r = cl.result();
261 CompactibleSpace* sp = r;
262 if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) {
263 sp = r->next_compaction_space();
264 }
265
266 G1PrepareCompactClosure blk(sp);
267 g1h->heap_region_iterate(&blk);
268
269 CompactPoint perm_cp(pg, NULL, NULL);
270 pg->prepare_for_compaction(&perm_cp);
271 }
272
273 class G1AdjustPointersClosure: public HeapRegionClosure {
274 public:
275 bool doHeapRegion(HeapRegion* r) {
276 if (r->isHumongous()) {
277 if (r->startsHumongous()) {
278 // We must adjust the pointers on the single H object.
279 oop obj = oop(r->bottom());
280 debug_only(GenMarkSweep::track_interior_pointers(obj));
281 // point all the oops to the new location
282 obj->adjust_pointers();
283 debug_only(GenMarkSweep::check_interior_pointers());
284 }
285 } else {
286 // This really ought to be "as_CompactibleSpace"...
287 r->adjust_pointers();
288 }
289 return false;
290 }
291 };
292
293 void G1MarkSweep::mark_sweep_phase3() {
294 G1CollectedHeap* g1h = G1CollectedHeap::heap();
295 Generation* pg = g1h->perm_gen();
296
297 // Adjust the pointers to reflect the new locations
298 EventMark m("3 adjust pointers");
299 TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);
300 GenMarkSweep::trace("3");
301
302 SharedHeap* sh = SharedHeap::heap();
303
304 sh->process_strong_roots(true, // activate StrongRootsScope
305 true, // Collecting permanent generation.
306 SharedHeap::SO_AllClasses,
307 &GenMarkSweep::adjust_root_pointer_closure,
308 NULL, // do not touch code cache here
309 &GenMarkSweep::adjust_pointer_closure);
310
311 g1h->ref_processor()->weak_oops_do(&GenMarkSweep::adjust_root_pointer_closure);
312
313 // Now adjust pointers in remaining weak roots. (All of which should
314 // have been cleared if they pointed to non-surviving objects.)
315 g1h->g1_process_weak_roots(&GenMarkSweep::adjust_root_pointer_closure,
316 &GenMarkSweep::adjust_pointer_closure);
317
318 GenMarkSweep::adjust_marks();
319
320 G1AdjustPointersClosure blk;
321 g1h->heap_region_iterate(&blk);
322 pg->adjust_pointers();
323 }
324
325 class G1SpaceCompactClosure: public HeapRegionClosure {
326 public:
327 G1SpaceCompactClosure() {}
328
329 bool doHeapRegion(HeapRegion* hr) {
330 if (hr->isHumongous()) {
331 if (hr->startsHumongous()) {
332 oop obj = oop(hr->bottom());
333 if (obj->is_gc_marked()) {
334 obj->init_mark();
335 } else {
336 assert(hr->is_empty(), "Should have been cleared in phase 2.");
337 }
338 hr->reset_during_compaction();
339 }
340 } else {
341 hr->compact();
342 }
343 return false;
344 }
345 };
346
347 void G1MarkSweep::mark_sweep_phase4() {
348 // All pointers are now adjusted, move objects accordingly
349
350 // It is imperative that we traverse perm_gen first in phase4. All
351 // classes must be allocated earlier than their instances, and traversing
352 // perm_gen first makes sure that all klassOops have moved to their new
353 // location before any instance does a dispatch through it's klass!
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 (perm_gen first rather than last), 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 Generation* pg = g1h->perm_gen();
361
362 EventMark m("4 compact heap");
363 TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty);
364 GenMarkSweep::trace("4");
365
366 pg->compact();
367
368 G1SpaceCompactClosure blk;
369 g1h->heap_region_iterate(&blk);
370
371 }
372
373 // Local Variables: ***
374 // c-indentation-style: gnu ***
375 // End: ***