Mon, 23 Jun 2008 16:49:37 -0700
6718086: CMS assert: _concurrent_iteration_safe_limit update missed
Summary: Initialize the field correctly in ContiguousSpace's constructor and initialize() methods, using the latter for the survivor spaces upon initial construction or a subsequent resizing of the young generation. Add some missing Space sub-class constructors.
Reviewed-by: apetrusenko
1 /*
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23 */
25 #include "incls/_precompiled.incl"
26 #include "incls/_genMarkSweep.cpp.incl"
28 void GenMarkSweep::invoke_at_safepoint(int level, ReferenceProcessor* rp,
29 bool clear_all_softrefs) {
30 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
32 // hook up weak ref data so it can be used during Mark-Sweep
33 assert(ref_processor() == NULL, "no stomping");
34 _ref_processor = rp;
35 assert(rp != NULL, "should be non-NULL");
37 TraceTime t1("Full GC", PrintGC && !PrintGCDetails, true, gclog_or_tty);
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();
44 // Increment the invocation count for the permanent generation, since it is
45 // implicitly collected whenever we do a full mark sweep collection.
46 GenCollectedHeap* gch = GenCollectedHeap::heap();
47 gch->perm_gen()->stat_record()->invocations++;
49 // Capture heap size before collection for printing.
50 size_t gch_prev_used = gch->used();
52 // Some of the card table updates below assume that the perm gen is
53 // also being collected.
54 assert(level == gch->n_gens() - 1,
55 "All generations are being collected, ergo perm gen too.");
57 // Capture used regions for each generation that will be
58 // subject to collection, so that card table adjustments can
59 // be made intelligently (see clear / invalidate further below).
60 gch->save_used_regions(level, true /* perm */);
62 allocate_stacks();
64 mark_sweep_phase1(level, clear_all_softrefs);
66 mark_sweep_phase2();
68 // Don't add any more derived pointers during phase3
69 COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
70 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
72 mark_sweep_phase3(level);
74 VALIDATE_MARK_SWEEP_ONLY(
75 if (ValidateMarkSweep) {
76 guarantee(_root_refs_stack->length() == 0, "should be empty by now");
77 }
78 )
80 mark_sweep_phase4();
82 VALIDATE_MARK_SWEEP_ONLY(
83 if (ValidateMarkSweep) {
84 guarantee(_live_oops->length() == _live_oops_moved_to->length(),
85 "should be the same size");
86 }
87 )
89 restore_marks();
91 // Set saved marks for allocation profiler (and other things? -- dld)
92 // (Should this be in general part?)
93 gch->save_marks();
95 deallocate_stacks();
97 // If compaction completely evacuated all generations younger than this
98 // one, then we can clear the card table. Otherwise, we must invalidate
99 // it (consider all cards dirty). In the future, we might consider doing
100 // compaction within generations only, and doing card-table sliding.
101 bool all_empty = true;
102 for (int i = 0; all_empty && i < level; i++) {
103 Generation* g = gch->get_gen(i);
104 all_empty = all_empty && gch->get_gen(i)->used() == 0;
105 }
106 GenRemSet* rs = gch->rem_set();
107 // Clear/invalidate below make use of the "prev_used_regions" saved earlier.
108 if (all_empty) {
109 // We've evacuated all generations below us.
110 Generation* g = gch->get_gen(level);
111 rs->clear_into_younger(g, true /* perm */);
112 } else {
113 // Invalidate the cards corresponding to the currently used
114 // region and clear those corresponding to the evacuated region
115 // of all generations just collected (i.e. level and younger).
116 rs->invalidate_or_clear(gch->get_gen(level),
117 true /* younger */,
118 true /* perm */);
119 }
121 Threads::gc_epilogue();
122 CodeCache::gc_epilogue();
124 if (PrintGC && !PrintGCDetails) {
125 gch->print_heap_change(gch_prev_used);
126 }
128 // refs processing: clean slate
129 _ref_processor = NULL;
131 // Update heap occupancy information which is used as
132 // input to soft ref clearing policy at the next gc.
133 Universe::update_heap_info_at_gc();
135 // Update time of last gc for all generations we collected
136 // (which curently is all the generations in the heap).
137 gch->update_time_of_last_gc(os::javaTimeMillis());
138 }
140 void GenMarkSweep::allocate_stacks() {
141 GenCollectedHeap* gch = GenCollectedHeap::heap();
142 // Scratch request on behalf of oldest generation; will do no
143 // allocation.
144 ScratchBlock* scratch = gch->gather_scratch(gch->_gens[gch->_n_gens-1], 0);
146 // $$$ To cut a corner, we'll only use the first scratch block, and then
147 // revert to malloc.
148 if (scratch != NULL) {
149 _preserved_count_max =
150 scratch->num_words * HeapWordSize / sizeof(PreservedMark);
151 } else {
152 _preserved_count_max = 0;
153 }
155 _preserved_marks = (PreservedMark*)scratch;
156 _preserved_count = 0;
157 _preserved_mark_stack = NULL;
158 _preserved_oop_stack = NULL;
160 _marking_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(4000, true);
162 int size = SystemDictionary::number_of_classes() * 2;
163 _revisit_klass_stack = new (ResourceObj::C_HEAP) GrowableArray<Klass*>(size, true);
165 #ifdef VALIDATE_MARK_SWEEP
166 if (ValidateMarkSweep) {
167 _root_refs_stack = new (ResourceObj::C_HEAP) GrowableArray<void*>(100, true);
168 _other_refs_stack = new (ResourceObj::C_HEAP) GrowableArray<void*>(100, true);
169 _adjusted_pointers = new (ResourceObj::C_HEAP) GrowableArray<void*>(100, true);
170 _live_oops = new (ResourceObj::C_HEAP) GrowableArray<oop>(100, true);
171 _live_oops_moved_to = new (ResourceObj::C_HEAP) GrowableArray<oop>(100, true);
172 _live_oops_size = new (ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
173 }
174 if (RecordMarkSweepCompaction) {
175 if (_cur_gc_live_oops == NULL) {
176 _cur_gc_live_oops = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
177 _cur_gc_live_oops_moved_to = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
178 _cur_gc_live_oops_size = new(ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
179 _last_gc_live_oops = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
180 _last_gc_live_oops_moved_to = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
181 _last_gc_live_oops_size = new(ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
182 } else {
183 _cur_gc_live_oops->clear();
184 _cur_gc_live_oops_moved_to->clear();
185 _cur_gc_live_oops_size->clear();
186 }
187 }
188 #endif
189 }
192 void GenMarkSweep::deallocate_stacks() {
193 if (_preserved_oop_stack) {
194 delete _preserved_mark_stack;
195 _preserved_mark_stack = NULL;
196 delete _preserved_oop_stack;
197 _preserved_oop_stack = NULL;
198 }
200 delete _marking_stack;
201 delete _revisit_klass_stack;
203 #ifdef VALIDATE_MARK_SWEEP
204 if (ValidateMarkSweep) {
205 delete _root_refs_stack;
206 delete _other_refs_stack;
207 delete _adjusted_pointers;
208 delete _live_oops;
209 delete _live_oops_size;
210 delete _live_oops_moved_to;
211 _live_oops_index = 0;
212 _live_oops_index_at_perm = 0;
213 }
214 #endif
215 }
217 void GenMarkSweep::mark_sweep_phase1(int level,
218 bool clear_all_softrefs) {
219 // Recursively traverse all live objects and mark them
220 EventMark m("1 mark object");
221 TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
222 trace(" 1");
224 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
226 GenCollectedHeap* gch = GenCollectedHeap::heap();
228 // Because follow_root_closure is created statically, cannot
229 // use OopsInGenClosure constructor which takes a generation,
230 // as the Universe has not been created when the static constructors
231 // are run.
232 follow_root_closure.set_orig_generation(gch->get_gen(level));
234 gch->gen_process_strong_roots(level,
235 false, // Younger gens are not roots.
236 true, // Collecting permanent generation.
237 SharedHeap::SO_SystemClasses,
238 &follow_root_closure, &follow_root_closure);
240 // Process reference objects found during marking
241 {
242 ReferencePolicy *soft_ref_policy;
243 if (clear_all_softrefs) {
244 soft_ref_policy = new AlwaysClearPolicy();
245 } else {
246 #ifdef COMPILER2
247 soft_ref_policy = new LRUMaxHeapPolicy();
248 #else
249 soft_ref_policy = new LRUCurrentHeapPolicy();
250 #endif // COMPILER2
251 }
252 assert(soft_ref_policy != NULL,"No soft reference policy");
253 ref_processor()->process_discovered_references(
254 soft_ref_policy, &is_alive, &keep_alive,
255 &follow_stack_closure, NULL);
256 }
258 // Follow system dictionary roots and unload classes
259 bool purged_class = SystemDictionary::do_unloading(&is_alive);
261 // Follow code cache roots
262 CodeCache::do_unloading(&is_alive, &keep_alive, purged_class);
263 follow_stack(); // Flush marking stack
265 // Update subklass/sibling/implementor links of live klasses
266 follow_weak_klass_links();
267 assert(_marking_stack->is_empty(), "just drained");
269 // Visit symbol and interned string tables and delete unmarked oops
270 SymbolTable::unlink(&is_alive);
271 StringTable::unlink(&is_alive);
273 assert(_marking_stack->is_empty(), "stack should be empty by now");
274 }
277 void GenMarkSweep::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 GenCollectedHeap* gch = GenCollectedHeap::heap();
292 Generation* pg = gch->perm_gen();
294 EventMark m("2 compute new addresses");
295 TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);
296 trace("2");
298 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
300 gch->prepare_for_compaction();
302 VALIDATE_MARK_SWEEP_ONLY(_live_oops_index_at_perm = _live_oops_index);
303 CompactPoint perm_cp(pg, NULL, NULL);
304 pg->prepare_for_compaction(&perm_cp);
305 }
307 class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure {
308 public:
309 void do_generation(Generation* gen) {
310 gen->adjust_pointers();
311 }
312 };
314 void GenMarkSweep::mark_sweep_phase3(int level) {
315 GenCollectedHeap* gch = GenCollectedHeap::heap();
316 Generation* pg = gch->perm_gen();
318 // Adjust the pointers to reflect the new locations
319 EventMark m("3 adjust pointers");
320 TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);
321 trace("3");
323 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
325 // Needs to be done before the system dictionary is adjusted.
326 pg->pre_adjust_pointers();
328 // Because the two closures below are created statically, cannot
329 // use OopsInGenClosure constructor which takes a generation,
330 // as the Universe has not been created when the static constructors
331 // are run.
332 adjust_root_pointer_closure.set_orig_generation(gch->get_gen(level));
333 adjust_pointer_closure.set_orig_generation(gch->get_gen(level));
335 gch->gen_process_strong_roots(level,
336 false, // Younger gens are not roots.
337 true, // Collecting permanent generation.
338 SharedHeap::SO_AllClasses,
339 &adjust_root_pointer_closure,
340 &adjust_root_pointer_closure);
342 // Now adjust pointers in remaining weak roots. (All of which should
343 // have been cleared if they pointed to non-surviving objects.)
344 gch->gen_process_weak_roots(&adjust_root_pointer_closure,
345 &adjust_pointer_closure);
347 adjust_marks();
348 GenAdjustPointersClosure blk;
349 gch->generation_iterate(&blk, true);
350 pg->adjust_pointers();
351 }
353 class GenCompactClosure: public GenCollectedHeap::GenClosure {
354 public:
355 void do_generation(Generation* gen) {
356 gen->compact();
357 }
358 };
360 void GenMarkSweep::mark_sweep_phase4() {
361 // All pointers are now adjusted, move objects accordingly
363 // It is imperative that we traverse perm_gen first in phase4. All
364 // classes must be allocated earlier than their instances, and traversing
365 // perm_gen first makes sure that all klassOops have moved to their new
366 // location before any instance does a dispatch through it's klass!
368 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
369 // in the same order in phase2, phase3 and phase4. We don't quite do that
370 // here (perm_gen first rather than last), so we tell the validate code
371 // to use a higher index (saved from phase2) when verifying perm_gen.
372 GenCollectedHeap* gch = GenCollectedHeap::heap();
373 Generation* pg = gch->perm_gen();
375 EventMark m("4 compact heap");
376 TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty);
377 trace("4");
379 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(true));
381 pg->compact();
383 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
385 GenCompactClosure blk;
386 gch->generation_iterate(&blk, true);
388 VALIDATE_MARK_SWEEP_ONLY(compaction_complete());
390 pg->post_compact(); // Shared spaces verification.
391 }