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 GenMarkSweep::_preserved_mark_stack = NULL;
127 GenMarkSweep::_preserved_oop_stack = NULL;
128
129 GenMarkSweep::_marking_stack =
130 new (ResourceObj::C_HEAP) GrowableArray<oop>(4000, true);
131 GenMarkSweep::_objarray_stack =
132 new (ResourceObj::C_HEAP) GrowableArray<ObjArrayTask>(50, true);
133
134 int size = SystemDictionary::number_of_classes() * 2;
135 GenMarkSweep::_revisit_klass_stack =
136 new (ResourceObj::C_HEAP) GrowableArray<Klass*>(size, true);
137 // (#klass/k)^2 for k ~ 10 appears a better fit, but this will have to do
138 // for now until we have a chance to work out a more optimal setting.
139 GenMarkSweep::_revisit_mdo_stack =
140 new (ResourceObj::C_HEAP) GrowableArray<DataLayout*>(size*2, true);
141
142 }
143
144 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
145 bool clear_all_softrefs) {
146 // Recursively traverse all live objects and mark them
147 EventMark m("1 mark object");
148 TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
149 GenMarkSweep::trace(" 1");
150
151 SharedHeap* sh = SharedHeap::heap();
152
153 sh->process_strong_roots(true, // activeate StrongRootsScope
154 true, // Collecting permanent generation.
155 SharedHeap::SO_SystemClasses,
156 &GenMarkSweep::follow_root_closure,
157 &GenMarkSweep::follow_code_root_closure,
158 &GenMarkSweep::follow_root_closure);
159
160 // Process reference objects found during marking
161 ReferenceProcessor* rp = GenMarkSweep::ref_processor();
162 rp->setup_policy(clear_all_softrefs);
163 rp->process_discovered_references(&GenMarkSweep::is_alive,
164 &GenMarkSweep::keep_alive,
165 &GenMarkSweep::follow_stack_closure,
166 NULL);
167
168 // Follow system dictionary roots and unload classes
169 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
170 assert(GenMarkSweep::_marking_stack->is_empty(),
171 "stack should be empty by now");
172
173 // Follow code cache roots (has to be done after system dictionary,
174 // assumes all live klasses are marked)
175 CodeCache::do_unloading(&GenMarkSweep::is_alive,
176 &GenMarkSweep::keep_alive,
177 purged_class);
178 GenMarkSweep::follow_stack();
179
180 // Update subklass/sibling/implementor links of live klasses
181 GenMarkSweep::follow_weak_klass_links();
182 assert(GenMarkSweep::_marking_stack->is_empty(),
183 "stack should be empty by now");
184
185 // Visit memoized MDO's and clear any unmarked weak refs
186 GenMarkSweep::follow_mdo_weak_refs();
187 assert(GenMarkSweep::_marking_stack->is_empty(), "just drained");
188
189
190 // Visit symbol and interned string tables and delete unmarked oops
191 SymbolTable::unlink(&GenMarkSweep::is_alive);
192 StringTable::unlink(&GenMarkSweep::is_alive);
193
194 assert(GenMarkSweep::_marking_stack->is_empty(),
195 "stack should be empty by now");
196 }
197
198 class G1PrepareCompactClosure: public HeapRegionClosure {
199 ModRefBarrierSet* _mrbs;
200 CompactPoint _cp;
201
202 void free_humongous_region(HeapRegion* hr) {
203 HeapWord* bot = hr->bottom();
204 HeapWord* end = hr->end();
205 assert(hr->startsHumongous(),
206 "Only the start of a humongous region should be freed.");
207 G1CollectedHeap::heap()->free_region(hr);
208 hr->prepare_for_compaction(&_cp);
209 // Also clear the part of the card table that will be unused after
210 // compaction.
211 _mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
212 }
213
214 public:
215 G1PrepareCompactClosure(CompactibleSpace* cs) :
216 _cp(NULL, cs, cs->initialize_threshold()),
217 _mrbs(G1CollectedHeap::heap()->mr_bs())
218 {}
219 bool doHeapRegion(HeapRegion* hr) {
220 if (hr->isHumongous()) {
221 if (hr->startsHumongous()) {
222 oop obj = oop(hr->bottom());
223 if (obj->is_gc_marked()) {
224 obj->forward_to(obj);
225 } else {
226 free_humongous_region(hr);
227 }
228 } else {
229 assert(hr->continuesHumongous(), "Invalid humongous.");
230 }
231 } else {
232 hr->prepare_for_compaction(&_cp);
233 // Also clear the part of the card table that will be unused after
234 // compaction.
235 _mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
236 }
237 return false;
238 }
239 };
240
241 // Finds the first HeapRegion.
242 class FindFirstRegionClosure: public HeapRegionClosure {
243 HeapRegion* _a_region;
244 public:
245 FindFirstRegionClosure() : _a_region(NULL) {}
246 bool doHeapRegion(HeapRegion* r) {
247 _a_region = r;
248 return true;
249 }
250 HeapRegion* result() { return _a_region; }
251 };
252
253 void G1MarkSweep::mark_sweep_phase2() {
254 // Now all live objects are marked, compute the new object addresses.
255
256 // It is imperative that we traverse perm_gen LAST. If dead space is
257 // allowed a range of dead object may get overwritten by a dead int
258 // array. If perm_gen is not traversed last a klassOop may get
259 // overwritten. This is fine since it is dead, but if the class has dead
260 // instances we have to skip them, and in order to find their size we
261 // need the klassOop!
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 Generation* pg = g1h->perm_gen();
269
270 EventMark m("2 compute new addresses");
271 TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);
272 GenMarkSweep::trace("2");
273
274 FindFirstRegionClosure cl;
275 g1h->heap_region_iterate(&cl);
276 HeapRegion *r = cl.result();
277 CompactibleSpace* sp = r;
278 if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) {
279 sp = r->next_compaction_space();
280 }
281
282 G1PrepareCompactClosure blk(sp);
283 g1h->heap_region_iterate(&blk);
284
285 CompactPoint perm_cp(pg, NULL, NULL);
286 pg->prepare_for_compaction(&perm_cp);
287 }
288
289 class G1AdjustPointersClosure: public HeapRegionClosure {
290 public:
291 bool doHeapRegion(HeapRegion* r) {
292 if (r->isHumongous()) {
293 if (r->startsHumongous()) {
294 // We must adjust the pointers on the single H object.
295 oop obj = oop(r->bottom());
296 debug_only(GenMarkSweep::track_interior_pointers(obj));
297 // point all the oops to the new location
298 obj->adjust_pointers();
299 debug_only(GenMarkSweep::check_interior_pointers());
300 }
301 } else {
302 // This really ought to be "as_CompactibleSpace"...
303 r->adjust_pointers();
304 }
305 return false;
306 }
307 };
308
309 void G1MarkSweep::mark_sweep_phase3() {
310 G1CollectedHeap* g1h = G1CollectedHeap::heap();
311 Generation* pg = g1h->perm_gen();
312
313 // Adjust the pointers to reflect the new locations
314 EventMark m("3 adjust pointers");
315 TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);
316 GenMarkSweep::trace("3");
317
318 SharedHeap* sh = SharedHeap::heap();
319
320 sh->process_strong_roots(true, // activate StrongRootsScope
321 true, // Collecting permanent generation.
322 SharedHeap::SO_AllClasses,
323 &GenMarkSweep::adjust_root_pointer_closure,
324 NULL, // do not touch code cache here
325 &GenMarkSweep::adjust_pointer_closure);
326
327 g1h->ref_processor()->weak_oops_do(&GenMarkSweep::adjust_root_pointer_closure);
328
329 // Now adjust pointers in remaining weak roots. (All of which should
330 // have been cleared if they pointed to non-surviving objects.)
331 g1h->g1_process_weak_roots(&GenMarkSweep::adjust_root_pointer_closure,
332 &GenMarkSweep::adjust_pointer_closure);
333
334 GenMarkSweep::adjust_marks();
335
336 G1AdjustPointersClosure blk;
337 g1h->heap_region_iterate(&blk);
338 pg->adjust_pointers();
339 }
340
341 class G1SpaceCompactClosure: public HeapRegionClosure {
342 public:
343 G1SpaceCompactClosure() {}
344
345 bool doHeapRegion(HeapRegion* hr) {
346 if (hr->isHumongous()) {
347 if (hr->startsHumongous()) {
348 oop obj = oop(hr->bottom());
349 if (obj->is_gc_marked()) {
350 obj->init_mark();
351 } else {
352 assert(hr->is_empty(), "Should have been cleared in phase 2.");
353 }
354 hr->reset_during_compaction();
355 }
356 } else {
357 hr->compact();
358 }
359 return false;
360 }
361 };
362
363 void G1MarkSweep::mark_sweep_phase4() {
364 // All pointers are now adjusted, move objects accordingly
365
366 // It is imperative that we traverse perm_gen first in phase4. All
367 // classes must be allocated earlier than their instances, and traversing
368 // perm_gen first makes sure that all klassOops have moved to their new
369 // location before any instance does a dispatch through it's klass!
370
371 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
372 // in the same order in phase2, phase3 and phase4. We don't quite do that
373 // here (perm_gen first rather than last), so we tell the validate code
374 // to use a higher index (saved from phase2) when verifying perm_gen.
375 G1CollectedHeap* g1h = G1CollectedHeap::heap();
376 Generation* pg = g1h->perm_gen();
377
378 EventMark m("4 compact heap");
379 TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty);
380 GenMarkSweep::trace("4");
381
382 pg->compact();
383
384 G1SpaceCompactClosure blk;
385 g1h->heap_region_iterate(&blk);
386
387 }
388
389 // Local Variables: ***
390 // c-indentation-style: gnu ***
391 // End: ***