Mon, 16 Apr 2012 08:57:18 +0200
4988100: oop_verify_old_oop appears to be dead
Summary: removed oop_verify_old_oop and allow_dirty. Also reviewed by: alexlamsl@gmail.com
Reviewed-by: jmasa, jwilhelm
1 /*
2 * Copyright (c) 2001, 2012, 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 */
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 "memory/gcLocker.hpp"
35 #include "memory/genCollectedHeap.hpp"
36 #include "memory/modRefBarrierSet.hpp"
37 #include "memory/referencePolicy.hpp"
38 #include "memory/space.hpp"
39 #include "oops/instanceRefKlass.hpp"
40 #include "oops/oop.inline.hpp"
41 #include "prims/jvmtiExport.hpp"
42 #include "runtime/aprofiler.hpp"
43 #include "runtime/biasedLocking.hpp"
44 #include "runtime/fprofiler.hpp"
45 #include "runtime/synchronizer.hpp"
46 #include "runtime/thread.hpp"
47 #include "runtime/vmThread.hpp"
48 #include "utilities/copy.hpp"
49 #include "utilities/events.hpp"
51 class HeapRegion;
53 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
54 bool clear_all_softrefs) {
55 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
57 SharedHeap* sh = SharedHeap::heap();
58 #ifdef ASSERT
59 if (sh->collector_policy()->should_clear_all_soft_refs()) {
60 assert(clear_all_softrefs, "Policy should have been checked earler");
61 }
62 #endif
63 // hook up weak ref data so it can be used during Mark-Sweep
64 assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
65 assert(rp != NULL, "should be non-NULL");
66 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition");
68 GenMarkSweep::_ref_processor = rp;
69 rp->setup_policy(clear_all_softrefs);
71 // When collecting the permanent generation methodOops may be moving,
72 // so we either have to flush all bcp data or convert it into bci.
73 CodeCache::gc_prologue();
74 Threads::gc_prologue();
76 // Increment the invocation count for the permanent generation, since it is
77 // implicitly collected whenever we do a full mark sweep collection.
78 sh->perm_gen()->stat_record()->invocations++;
80 bool marked_for_unloading = false;
82 allocate_stacks();
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();
88 mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
90 mark_sweep_phase2();
92 // Don't add any more derived pointers during phase3
93 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
95 mark_sweep_phase3();
97 mark_sweep_phase4();
99 GenMarkSweep::restore_marks();
100 BiasedLocking::restore_marks();
101 GenMarkSweep::deallocate_stacks();
103 // We must invalidate the perm-gen rs, so that it gets rebuilt.
104 GenRemSet* rs = sh->rem_set();
105 rs->invalidate(sh->perm_gen()->used_region(), true /*whole_heap*/);
107 // "free at last gc" is calculated from these.
108 // CHF: cheating for now!!!
109 // Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity());
110 // Universe::set_heap_used_at_last_gc(Universe::heap()->used());
112 Threads::gc_epilogue();
113 CodeCache::gc_epilogue();
114 JvmtiExport::gc_epilogue();
116 // refs processing: clean slate
117 GenMarkSweep::_ref_processor = NULL;
118 }
121 void G1MarkSweep::allocate_stacks() {
122 GenMarkSweep::_preserved_count_max = 0;
123 GenMarkSweep::_preserved_marks = NULL;
124 GenMarkSweep::_preserved_count = 0;
125 }
127 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
128 bool clear_all_softrefs) {
129 // Recursively traverse all live objects and mark them
130 TraceTime tm("phase 1", G1Log::fine() && Verbose, true, gclog_or_tty);
131 GenMarkSweep::trace(" 1");
133 SharedHeap* sh = SharedHeap::heap();
135 sh->process_strong_roots(true, // activeate StrongRootsScope
136 true, // Collecting permanent generation.
137 SharedHeap::SO_SystemClasses,
138 &GenMarkSweep::follow_root_closure,
139 &GenMarkSweep::follow_code_root_closure,
140 &GenMarkSweep::follow_root_closure);
142 // Process reference objects found during marking
143 ReferenceProcessor* rp = GenMarkSweep::ref_processor();
144 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Sanity");
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);
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");
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();
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");
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");
173 // Visit interned string tables and delete unmarked oops
174 StringTable::unlink(&GenMarkSweep::is_alive);
175 // Clean up unreferenced symbols in symbol table.
176 SymbolTable::unlink();
178 assert(GenMarkSweep::_marking_stack.is_empty(),
179 "stack should be empty by now");
181 if (VerifyDuringGC) {
182 HandleMark hm; // handle scope
183 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);
184 gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying ");
185 Universe::heap()->prepare_for_verify();
186 // Note: we can verify only the heap here. When an object is
187 // marked, the previous value of the mark word (including
188 // identity hash values, ages, etc) is preserved, and the mark
189 // word is set to markOop::marked_value - effectively removing
190 // any hash values from the mark word. These hash values are
191 // used when verifying the dictionaries and so removing them
192 // from the mark word can make verification of the dictionaries
193 // fail. At the end of the GC, the orginal mark word values
194 // (including hash values) are restored to the appropriate
195 // objects.
196 Universe::heap()->verify(/* silent */ false,
197 /* option */ VerifyOption_G1UseMarkWord);
199 G1CollectedHeap* g1h = G1CollectedHeap::heap();
200 gclog_or_tty->print_cr("]");
201 }
202 }
204 class G1PrepareCompactClosure: public HeapRegionClosure {
205 G1CollectedHeap* _g1h;
206 ModRefBarrierSet* _mrbs;
207 CompactPoint _cp;
208 HumongousRegionSet _humongous_proxy_set;
210 void free_humongous_region(HeapRegion* hr) {
211 HeapWord* end = hr->end();
212 size_t dummy_pre_used;
213 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
215 assert(hr->startsHumongous(),
216 "Only the start of a humongous region should be freed.");
217 _g1h->free_humongous_region(hr, &dummy_pre_used, &dummy_free_list,
218 &_humongous_proxy_set, false /* par */);
219 hr->prepare_for_compaction(&_cp);
220 // Also clear the part of the card table that will be unused after
221 // compaction.
222 _mrbs->clear(MemRegion(hr->compaction_top(), end));
223 dummy_free_list.remove_all();
224 }
226 public:
227 G1PrepareCompactClosure(CompactibleSpace* cs)
228 : _g1h(G1CollectedHeap::heap()),
229 _mrbs(G1CollectedHeap::heap()->mr_bs()),
230 _cp(NULL, cs, cs->initialize_threshold()),
231 _humongous_proxy_set("G1MarkSweep Humongous Proxy Set") { }
233 void update_sets() {
234 // We'll recalculate total used bytes and recreate the free list
235 // at the end of the GC, so no point in updating those values here.
236 _g1h->update_sets_after_freeing_regions(0, /* pre_used */
237 NULL, /* free_list */
238 NULL, /* old_proxy_set */
239 &_humongous_proxy_set,
240 false /* par */);
241 }
243 bool doHeapRegion(HeapRegion* hr) {
244 if (hr->isHumongous()) {
245 if (hr->startsHumongous()) {
246 oop obj = oop(hr->bottom());
247 if (obj->is_gc_marked()) {
248 obj->forward_to(obj);
249 } else {
250 free_humongous_region(hr);
251 }
252 } else {
253 assert(hr->continuesHumongous(), "Invalid humongous.");
254 }
255 } else {
256 hr->prepare_for_compaction(&_cp);
257 // Also clear the part of the card table that will be unused after
258 // compaction.
259 _mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
260 }
261 return false;
262 }
263 };
265 // Finds the first HeapRegion.
266 class FindFirstRegionClosure: public HeapRegionClosure {
267 HeapRegion* _a_region;
268 public:
269 FindFirstRegionClosure() : _a_region(NULL) {}
270 bool doHeapRegion(HeapRegion* r) {
271 _a_region = r;
272 return true;
273 }
274 HeapRegion* result() { return _a_region; }
275 };
277 void G1MarkSweep::mark_sweep_phase2() {
278 // Now all live objects are marked, compute the new object addresses.
280 // It is imperative that we traverse perm_gen LAST. If dead space is
281 // allowed a range of dead object may get overwritten by a dead int
282 // array. If perm_gen is not traversed last a klassOop may get
283 // overwritten. This is fine since it is dead, but if the class has dead
284 // instances we have to skip them, and in order to find their size we
285 // need the klassOop!
286 //
287 // It is not required that we traverse spaces in the same order in
288 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
289 // tracking expects us to do so. See comment under phase4.
291 G1CollectedHeap* g1h = G1CollectedHeap::heap();
292 Generation* pg = g1h->perm_gen();
294 TraceTime tm("phase 2", G1Log::fine() && Verbose, true, gclog_or_tty);
295 GenMarkSweep::trace("2");
297 FindFirstRegionClosure cl;
298 g1h->heap_region_iterate(&cl);
299 HeapRegion *r = cl.result();
300 CompactibleSpace* sp = r;
301 if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) {
302 sp = r->next_compaction_space();
303 }
305 G1PrepareCompactClosure blk(sp);
306 g1h->heap_region_iterate(&blk);
307 blk.update_sets();
309 CompactPoint perm_cp(pg, NULL, NULL);
310 pg->prepare_for_compaction(&perm_cp);
311 }
313 class G1AdjustPointersClosure: public HeapRegionClosure {
314 public:
315 bool doHeapRegion(HeapRegion* r) {
316 if (r->isHumongous()) {
317 if (r->startsHumongous()) {
318 // We must adjust the pointers on the single H object.
319 oop obj = oop(r->bottom());
320 debug_only(GenMarkSweep::track_interior_pointers(obj));
321 // point all the oops to the new location
322 obj->adjust_pointers();
323 debug_only(GenMarkSweep::check_interior_pointers());
324 }
325 } else {
326 // This really ought to be "as_CompactibleSpace"...
327 r->adjust_pointers();
328 }
329 return false;
330 }
331 };
333 void G1MarkSweep::mark_sweep_phase3() {
334 G1CollectedHeap* g1h = G1CollectedHeap::heap();
335 Generation* pg = g1h->perm_gen();
337 // Adjust the pointers to reflect the new locations
338 TraceTime tm("phase 3", G1Log::fine() && Verbose, true, gclog_or_tty);
339 GenMarkSweep::trace("3");
341 SharedHeap* sh = SharedHeap::heap();
343 sh->process_strong_roots(true, // activate StrongRootsScope
344 true, // Collecting permanent generation.
345 SharedHeap::SO_AllClasses,
346 &GenMarkSweep::adjust_root_pointer_closure,
347 NULL, // do not touch code cache here
348 &GenMarkSweep::adjust_pointer_closure);
350 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
351 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_root_pointer_closure);
353 // Now adjust pointers in remaining weak roots. (All of which should
354 // have been cleared if they pointed to non-surviving objects.)
355 g1h->g1_process_weak_roots(&GenMarkSweep::adjust_root_pointer_closure,
356 &GenMarkSweep::adjust_pointer_closure);
358 GenMarkSweep::adjust_marks();
360 G1AdjustPointersClosure blk;
361 g1h->heap_region_iterate(&blk);
362 pg->adjust_pointers();
363 }
365 class G1SpaceCompactClosure: public HeapRegionClosure {
366 public:
367 G1SpaceCompactClosure() {}
369 bool doHeapRegion(HeapRegion* hr) {
370 if (hr->isHumongous()) {
371 if (hr->startsHumongous()) {
372 oop obj = oop(hr->bottom());
373 if (obj->is_gc_marked()) {
374 obj->init_mark();
375 } else {
376 assert(hr->is_empty(), "Should have been cleared in phase 2.");
377 }
378 hr->reset_during_compaction();
379 }
380 } else {
381 hr->compact();
382 }
383 return false;
384 }
385 };
387 void G1MarkSweep::mark_sweep_phase4() {
388 // All pointers are now adjusted, move objects accordingly
390 // It is imperative that we traverse perm_gen first in phase4. All
391 // classes must be allocated earlier than their instances, and traversing
392 // perm_gen first makes sure that all klassOops have moved to their new
393 // location before any instance does a dispatch through it's klass!
395 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
396 // in the same order in phase2, phase3 and phase4. We don't quite do that
397 // here (perm_gen first rather than last), so we tell the validate code
398 // to use a higher index (saved from phase2) when verifying perm_gen.
399 G1CollectedHeap* g1h = G1CollectedHeap::heap();
400 Generation* pg = g1h->perm_gen();
402 TraceTime tm("phase 4", G1Log::fine() && Verbose, true, gclog_or_tty);
403 GenMarkSweep::trace("4");
405 pg->compact();
407 G1SpaceCompactClosure blk;
408 g1h->heap_region_iterate(&blk);
410 }
412 // Local Variables: ***
413 // c-indentation-style: gnu ***
414 // End: ***