1 /*
2 * Copyright 2001-2007 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
24
25 #include "incls/_precompiled.incl"
26 #include "incls/_g1MarkSweep.cpp.incl"
27
28 class HeapRegion;
29
30 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
31 bool clear_all_softrefs) {
32 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
33
34 // hook up weak ref data so it can be used during Mark-Sweep
35 assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
36 GenMarkSweep::_ref_processor = rp;
37 assert(rp != NULL, "should be non-NULL");
38
39 // When collecting the permanent generation methodOops may be moving,
40 // so we either have to flush all bcp data or convert it into bci.
41 CodeCache::gc_prologue();
42 Threads::gc_prologue();
43
44 // Increment the invocation count for the permanent generation, since it is
45 // implicitly collected whenever we do a full mark sweep collection.
46 SharedHeap* sh = SharedHeap::heap();
47 sh->perm_gen()->stat_record()->invocations++;
48
49 bool marked_for_unloading = false;
50
51 allocate_stacks();
52
53 // We should save the marks of the currently locked biased monitors.
54 // The marking doesn't preserve the marks of biased objects.
55 BiasedLocking::preserve_marks();
56
57 mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
58
59 if (G1VerifyConcMark) {
60 G1CollectedHeap* g1h = G1CollectedHeap::heap();
61 g1h->checkConcurrentMark();
62 }
63
64 mark_sweep_phase2();
65
66 // Don't add any more derived pointers during phase3
67 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
68
69 mark_sweep_phase3();
70
71 mark_sweep_phase4();
72
73 GenMarkSweep::restore_marks();
74 BiasedLocking::restore_marks();
75 GenMarkSweep::deallocate_stacks();
76
77 // We must invalidate the perm-gen rs, so that it gets rebuilt.
78 GenRemSet* rs = sh->rem_set();
79 rs->invalidate(sh->perm_gen()->used_region(), true /*whole_heap*/);
80
81 // "free at last gc" is calculated from these.
82 // CHF: cheating for now!!!
83 // Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity());
84 // Universe::set_heap_used_at_last_gc(Universe::heap()->used());
85
86 Threads::gc_epilogue();
87 CodeCache::gc_epilogue();
88
89 // refs processing: clean slate
90 GenMarkSweep::_ref_processor = NULL;
91 }
92
93
94 void G1MarkSweep::allocate_stacks() {
95 GenMarkSweep::_preserved_count_max = 0;
96 GenMarkSweep::_preserved_marks = NULL;
97 GenMarkSweep::_preserved_count = 0;
98 GenMarkSweep::_preserved_mark_stack = NULL;
99 GenMarkSweep::_preserved_oop_stack = NULL;
100
101 GenMarkSweep::_marking_stack =
102 new (ResourceObj::C_HEAP) GrowableArray<oop>(4000, true);
103
104 size_t size = SystemDictionary::number_of_classes() * 2;
105 GenMarkSweep::_revisit_klass_stack =
106 new (ResourceObj::C_HEAP) GrowableArray<Klass*>((int)size, true);
107 }
108
109 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
110 bool clear_all_softrefs) {
111 // Recursively traverse all live objects and mark them
112 EventMark m("1 mark object");
113 TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
114 GenMarkSweep::trace(" 1");
115
116 SharedHeap* sh = SharedHeap::heap();
117
118 sh->process_strong_roots(true, // Collecting permanent generation.
119 SharedHeap::SO_SystemClasses,
120 &GenMarkSweep::follow_root_closure,
121 &GenMarkSweep::follow_root_closure);
122
123 // Process reference objects found during marking
124 ReferencePolicy *soft_ref_policy;
125 if (clear_all_softrefs) {
126 soft_ref_policy = new AlwaysClearPolicy();
127 } else {
128 #ifdef COMPILER2
129 soft_ref_policy = new LRUMaxHeapPolicy();
130 #else
131 soft_ref_policy = new LRUCurrentHeapPolicy();
132 #endif
133 }
134 assert(soft_ref_policy != NULL,"No soft reference policy");
135 GenMarkSweep::ref_processor()->process_discovered_references(
136 soft_ref_policy,
137 &GenMarkSweep::is_alive,
138 &GenMarkSweep::keep_alive,
139 &GenMarkSweep::follow_stack_closure,
140 NULL);
141
142 // Follow system dictionary roots and unload classes
143 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
144 assert(GenMarkSweep::_marking_stack->is_empty(),
145 "stack should be empty by now");
146
147 // Follow code cache roots (has to be done after system dictionary,
148 // assumes all live klasses are marked)
149 CodeCache::do_unloading(&GenMarkSweep::is_alive,
150 &GenMarkSweep::keep_alive,
151 purged_class);
152 GenMarkSweep::follow_stack();
153
154 // Update subklass/sibling/implementor links of live klasses
155 GenMarkSweep::follow_weak_klass_links();
156 assert(GenMarkSweep::_marking_stack->is_empty(),
157 "stack should be empty by now");
158
159 // Visit symbol and interned string tables and delete unmarked oops
160 SymbolTable::unlink(&GenMarkSweep::is_alive);
161 StringTable::unlink(&GenMarkSweep::is_alive);
162
163 assert(GenMarkSweep::_marking_stack->is_empty(),
164 "stack should be empty by now");
165 }
166
167 class G1PrepareCompactClosure: public HeapRegionClosure {
168 ModRefBarrierSet* _mrbs;
169 CompactPoint _cp;
170 bool _popular_only;
171
172 void free_humongous_region(HeapRegion* hr) {
173 HeapWord* bot = hr->bottom();
174 HeapWord* end = hr->end();
175 assert(hr->startsHumongous(),
176 "Only the start of a humongous region should be freed.");
177 G1CollectedHeap::heap()->free_region(hr);
178 hr->prepare_for_compaction(&_cp);
179 // Also clear the part of the card table that will be unused after
180 // compaction.
181 _mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
182 }
183
184 public:
185 G1PrepareCompactClosure(CompactibleSpace* cs, bool popular_only) :
186 _cp(NULL, cs, cs->initialize_threshold()),
187 _mrbs(G1CollectedHeap::heap()->mr_bs()),
188 _popular_only(popular_only)
189 {}
190 bool doHeapRegion(HeapRegion* hr) {
191 if (_popular_only && !hr->popular())
192 return true; // terminate early
193 else if (!_popular_only && hr->popular())
194 return false; // skip this one.
195
196 if (hr->isHumongous()) {
197 if (hr->startsHumongous()) {
198 oop obj = oop(hr->bottom());
199 if (obj->is_gc_marked()) {
200 obj->forward_to(obj);
201 } else {
202 free_humongous_region(hr);
203 }
204 } else {
205 assert(hr->continuesHumongous(), "Invalid humongous.");
206 }
207 } else {
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 return false;
214 }
215 };
216 // Stolen verbatim from g1CollectedHeap.cpp
217 class FindFirstRegionClosure: public HeapRegionClosure {
218 HeapRegion* _a_region;
219 bool _find_popular;
220 public:
221 FindFirstRegionClosure(bool find_popular) :
222 _a_region(NULL), _find_popular(find_popular) {}
223 bool doHeapRegion(HeapRegion* r) {
224 if (r->popular() == _find_popular) {
225 _a_region = r;
226 return true;
227 } else {
228 return false;
229 }
230 }
231 HeapRegion* result() { return _a_region; }
232 };
233
234 void G1MarkSweep::mark_sweep_phase2() {
235 // Now all live objects are marked, compute the new object addresses.
236
237 // It is imperative that we traverse perm_gen LAST. If dead space is
238 // allowed a range of dead object may get overwritten by a dead int
239 // array. If perm_gen is not traversed last a klassOop may get
240 // overwritten. This is fine since it is dead, but if the class has dead
241 // instances we have to skip them, and in order to find their size we
242 // need the klassOop!
243 //
244 // It is not required that we traverse spaces in the same order in
245 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
246 // tracking expects us to do so. See comment under phase4.
247
248 G1CollectedHeap* g1h = G1CollectedHeap::heap();
249 Generation* pg = g1h->perm_gen();
250
251 EventMark m("2 compute new addresses");
252 TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);
253 GenMarkSweep::trace("2");
254
255 // First we compact the popular regions.
256 if (G1NumPopularRegions > 0) {
257 CompactibleSpace* sp = g1h->first_compactible_space();
258 FindFirstRegionClosure cl(true /*find_popular*/);
259 g1h->heap_region_iterate(&cl);
260 HeapRegion *r = cl.result();
261 assert(r->popular(), "should have found a popular region.");
262 assert(r == sp, "first popular heap region should "
263 "== first compactible space");
264 G1PrepareCompactClosure blk(sp, true/*popular_only*/);
265 g1h->heap_region_iterate(&blk);
266 }
267
268 // Now we do the regular regions.
269 FindFirstRegionClosure cl(false /*find_popular*/);
270 g1h->heap_region_iterate(&cl);
271 HeapRegion *r = cl.result();
272 assert(!r->popular(), "should have founda non-popular region.");
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, false/*popular_only*/);
279 g1h->heap_region_iterate(&blk);
280
281 CompactPoint perm_cp(pg, NULL, NULL);
282 pg->prepare_for_compaction(&perm_cp);
283 }
284
285 class G1AdjustPointersClosure: public HeapRegionClosure {
286 public:
287 bool doHeapRegion(HeapRegion* r) {
288 if (r->isHumongous()) {
289 if (r->startsHumongous()) {
290 // We must adjust the pointers on the single H object.
291 oop obj = oop(r->bottom());
292 debug_only(GenMarkSweep::track_interior_pointers(obj));
293 // point all the oops to the new location
294 obj->adjust_pointers();
295 debug_only(GenMarkSweep::check_interior_pointers());
296 }
297 } else {
298 // This really ought to be "as_CompactibleSpace"...
299 r->adjust_pointers();
300 }
301 return false;
302 }
303 };
304
305 void G1MarkSweep::mark_sweep_phase3() {
306 G1CollectedHeap* g1h = G1CollectedHeap::heap();
307 Generation* pg = g1h->perm_gen();
308
309 // Adjust the pointers to reflect the new locations
310 EventMark m("3 adjust pointers");
311 TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);
312 GenMarkSweep::trace("3");
313
314 SharedHeap* sh = SharedHeap::heap();
315
316 sh->process_strong_roots(true, // Collecting permanent generation.
317 SharedHeap::SO_AllClasses,
318 &GenMarkSweep::adjust_root_pointer_closure,
319 &GenMarkSweep::adjust_pointer_closure);
320
321 g1h->ref_processor()->weak_oops_do(&GenMarkSweep::adjust_root_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_root_pointer_closure,
326 &GenMarkSweep::adjust_pointer_closure);
327
328 GenMarkSweep::adjust_marks();
329
330 G1AdjustPointersClosure blk;
331 g1h->heap_region_iterate(&blk);
332 pg->adjust_pointers();
333 }
334
335 class G1SpaceCompactClosure: public HeapRegionClosure {
336 public:
337 G1SpaceCompactClosure() {}
338
339 bool doHeapRegion(HeapRegion* hr) {
340 if (hr->isHumongous()) {
341 if (hr->startsHumongous()) {
342 oop obj = oop(hr->bottom());
343 if (obj->is_gc_marked()) {
344 obj->init_mark();
345 } else {
346 assert(hr->is_empty(), "Should have been cleared in phase 2.");
347 }
348 hr->reset_during_compaction();
349 }
350 } else {
351 hr->compact();
352 }
353 return false;
354 }
355 };
356
357 void G1MarkSweep::mark_sweep_phase4() {
358 // All pointers are now adjusted, move objects accordingly
359
360 // It is imperative that we traverse perm_gen first in phase4. All
361 // classes must be allocated earlier than their instances, and traversing
362 // perm_gen first makes sure that all klassOops have moved to their new
363 // location before any instance does a dispatch through it's klass!
364
365 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
366 // in the same order in phase2, phase3 and phase4. We don't quite do that
367 // here (perm_gen first rather than last), so we tell the validate code
368 // to use a higher index (saved from phase2) when verifying perm_gen.
369 G1CollectedHeap* g1h = G1CollectedHeap::heap();
370 Generation* pg = g1h->perm_gen();
371
372 EventMark m("4 compact heap");
373 TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty);
374 GenMarkSweep::trace("4");
375
376 pg->compact();
377
378 G1SpaceCompactClosure blk;
379 g1h->heap_region_iterate(&blk);
380
381 }
382
383 // Local Variables: ***
384 // c-indentation-style: gnu ***
385 // End: ***