Fri, 09 Oct 2009 15:18:52 -0700
Merge
1 /*
2 * Copyright 2001-2009 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 */
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 assert(rp != NULL, "should be non-NULL");
35 _ref_processor = rp;
36 rp->setup_policy(clear_all_softrefs);
38 TraceTime t1("Full GC", PrintGC && !PrintGCDetails, true, gclog_or_tty);
40 // When collecting the permanent generation methodOops may be moving,
41 // so we either have to flush all bcp data or convert it into bci.
42 CodeCache::gc_prologue();
43 Threads::gc_prologue();
45 // Increment the invocation count for the permanent generation, since it is
46 // implicitly collected whenever we do a full mark sweep collection.
47 GenCollectedHeap* gch = GenCollectedHeap::heap();
48 gch->perm_gen()->stat_record()->invocations++;
50 // Capture heap size before collection for printing.
51 size_t gch_prev_used = gch->used();
53 // Some of the card table updates below assume that the perm gen is
54 // also being collected.
55 assert(level == gch->n_gens() - 1,
56 "All generations are being collected, ergo perm gen too.");
58 // Capture used regions for each generation that will be
59 // subject to collection, so that card table adjustments can
60 // be made intelligently (see clear / invalidate further below).
61 gch->save_used_regions(level, true /* perm */);
63 allocate_stacks();
65 mark_sweep_phase1(level, clear_all_softrefs);
67 mark_sweep_phase2();
69 // Don't add any more derived pointers during phase3
70 COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
71 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
73 mark_sweep_phase3(level);
75 VALIDATE_MARK_SWEEP_ONLY(
76 if (ValidateMarkSweep) {
77 guarantee(_root_refs_stack->length() == 0, "should be empty by now");
78 }
79 )
81 mark_sweep_phase4();
83 VALIDATE_MARK_SWEEP_ONLY(
84 if (ValidateMarkSweep) {
85 guarantee(_live_oops->length() == _live_oops_moved_to->length(),
86 "should be the same size");
87 }
88 )
90 restore_marks();
92 // Set saved marks for allocation profiler (and other things? -- dld)
93 // (Should this be in general part?)
94 gch->save_marks();
96 deallocate_stacks();
98 // If compaction completely evacuated all generations younger than this
99 // one, then we can clear the card table. Otherwise, we must invalidate
100 // it (consider all cards dirty). In the future, we might consider doing
101 // compaction within generations only, and doing card-table sliding.
102 bool all_empty = true;
103 for (int i = 0; all_empty && i < level; i++) {
104 Generation* g = gch->get_gen(i);
105 all_empty = all_empty && gch->get_gen(i)->used() == 0;
106 }
107 GenRemSet* rs = gch->rem_set();
108 // Clear/invalidate below make use of the "prev_used_regions" saved earlier.
109 if (all_empty) {
110 // We've evacuated all generations below us.
111 Generation* g = gch->get_gen(level);
112 rs->clear_into_younger(g, true /* perm */);
113 } else {
114 // Invalidate the cards corresponding to the currently used
115 // region and clear those corresponding to the evacuated region
116 // of all generations just collected (i.e. level and younger).
117 rs->invalidate_or_clear(gch->get_gen(level),
118 true /* younger */,
119 true /* perm */);
120 }
122 Threads::gc_epilogue();
123 CodeCache::gc_epilogue();
125 if (PrintGC && !PrintGCDetails) {
126 gch->print_heap_change(gch_prev_used);
127 }
129 // refs processing: clean slate
130 _ref_processor = NULL;
132 // Update heap occupancy information which is used as
133 // input to soft ref clearing policy at the next gc.
134 Universe::update_heap_info_at_gc();
136 // Update time of last gc for all generations we collected
137 // (which curently is all the generations in the heap).
138 gch->update_time_of_last_gc(os::javaTimeMillis());
139 }
141 void GenMarkSweep::allocate_stacks() {
142 GenCollectedHeap* gch = GenCollectedHeap::heap();
143 // Scratch request on behalf of oldest generation; will do no
144 // allocation.
145 ScratchBlock* scratch = gch->gather_scratch(gch->_gens[gch->_n_gens-1], 0);
147 // $$$ To cut a corner, we'll only use the first scratch block, and then
148 // revert to malloc.
149 if (scratch != NULL) {
150 _preserved_count_max =
151 scratch->num_words * HeapWordSize / sizeof(PreservedMark);
152 } else {
153 _preserved_count_max = 0;
154 }
156 _preserved_marks = (PreservedMark*)scratch;
157 _preserved_count = 0;
158 _preserved_mark_stack = NULL;
159 _preserved_oop_stack = NULL;
161 _marking_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(4000, true);
163 int size = SystemDictionary::number_of_classes() * 2;
164 _revisit_klass_stack = new (ResourceObj::C_HEAP) GrowableArray<Klass*>(size, true);
165 // (#klass/k)^2 for k ~ 10 appears to be a better fit, but this will have to do for
166 // now until we have had a chance to investigate a more optimal setting.
167 _revisit_mdo_stack = new (ResourceObj::C_HEAP) GrowableArray<DataLayout*>(2*size, true);
169 #ifdef VALIDATE_MARK_SWEEP
170 if (ValidateMarkSweep) {
171 _root_refs_stack = new (ResourceObj::C_HEAP) GrowableArray<void*>(100, true);
172 _other_refs_stack = new (ResourceObj::C_HEAP) GrowableArray<void*>(100, true);
173 _adjusted_pointers = new (ResourceObj::C_HEAP) GrowableArray<void*>(100, true);
174 _live_oops = new (ResourceObj::C_HEAP) GrowableArray<oop>(100, true);
175 _live_oops_moved_to = new (ResourceObj::C_HEAP) GrowableArray<oop>(100, true);
176 _live_oops_size = new (ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
177 }
178 if (RecordMarkSweepCompaction) {
179 if (_cur_gc_live_oops == NULL) {
180 _cur_gc_live_oops = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
181 _cur_gc_live_oops_moved_to = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
182 _cur_gc_live_oops_size = new(ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
183 _last_gc_live_oops = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
184 _last_gc_live_oops_moved_to = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
185 _last_gc_live_oops_size = new(ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
186 } else {
187 _cur_gc_live_oops->clear();
188 _cur_gc_live_oops_moved_to->clear();
189 _cur_gc_live_oops_size->clear();
190 }
191 }
192 #endif
193 }
196 void GenMarkSweep::deallocate_stacks() {
198 if (!UseG1GC) {
199 GenCollectedHeap* gch = GenCollectedHeap::heap();
200 gch->release_scratch();
201 }
203 if (_preserved_oop_stack) {
204 delete _preserved_mark_stack;
205 _preserved_mark_stack = NULL;
206 delete _preserved_oop_stack;
207 _preserved_oop_stack = NULL;
208 }
210 delete _marking_stack;
211 delete _revisit_klass_stack;
212 delete _revisit_mdo_stack;
214 #ifdef VALIDATE_MARK_SWEEP
215 if (ValidateMarkSweep) {
216 delete _root_refs_stack;
217 delete _other_refs_stack;
218 delete _adjusted_pointers;
219 delete _live_oops;
220 delete _live_oops_size;
221 delete _live_oops_moved_to;
222 _live_oops_index = 0;
223 _live_oops_index_at_perm = 0;
224 }
225 #endif
226 }
228 void GenMarkSweep::mark_sweep_phase1(int level,
229 bool clear_all_softrefs) {
230 // Recursively traverse all live objects and mark them
231 EventMark m("1 mark object");
232 TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
233 trace(" 1");
235 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
237 GenCollectedHeap* gch = GenCollectedHeap::heap();
239 // Because follow_root_closure is created statically, cannot
240 // use OopsInGenClosure constructor which takes a generation,
241 // as the Universe has not been created when the static constructors
242 // are run.
243 follow_root_closure.set_orig_generation(gch->get_gen(level));
245 gch->gen_process_strong_roots(level,
246 false, // Younger gens are not roots.
247 true, // activate StrongRootsScope
248 true, // Collecting permanent generation.
249 SharedHeap::SO_SystemClasses,
250 &follow_root_closure,
251 true, // walk code active on stacks
252 &follow_root_closure);
254 // Process reference objects found during marking
255 {
256 ref_processor()->setup_policy(clear_all_softrefs);
257 ref_processor()->process_discovered_references(
258 &is_alive, &keep_alive, &follow_stack_closure, NULL);
259 }
261 // Follow system dictionary roots and unload classes
262 bool purged_class = SystemDictionary::do_unloading(&is_alive);
264 // Follow code cache roots
265 CodeCache::do_unloading(&is_alive, &keep_alive, purged_class);
266 follow_stack(); // Flush marking stack
268 // Update subklass/sibling/implementor links of live klasses
269 follow_weak_klass_links();
270 assert(_marking_stack->is_empty(), "just drained");
272 // Visit memoized MDO's and clear any unmarked weak refs
273 follow_mdo_weak_refs();
274 assert(_marking_stack->is_empty(), "just drained");
276 // Visit symbol and interned string tables and delete unmarked oops
277 SymbolTable::unlink(&is_alive);
278 StringTable::unlink(&is_alive);
280 assert(_marking_stack->is_empty(), "stack should be empty by now");
281 }
284 void GenMarkSweep::mark_sweep_phase2() {
285 // Now all live objects are marked, compute the new object addresses.
287 // It is imperative that we traverse perm_gen LAST. If dead space is
288 // allowed a range of dead object may get overwritten by a dead int
289 // array. If perm_gen is not traversed last a klassOop may get
290 // overwritten. This is fine since it is dead, but if the class has dead
291 // instances we have to skip them, and in order to find their size we
292 // need the klassOop!
293 //
294 // It is not required that we traverse spaces in the same order in
295 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
296 // tracking expects us to do so. See comment under phase4.
298 GenCollectedHeap* gch = GenCollectedHeap::heap();
299 Generation* pg = gch->perm_gen();
301 EventMark m("2 compute new addresses");
302 TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);
303 trace("2");
305 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
307 gch->prepare_for_compaction();
309 VALIDATE_MARK_SWEEP_ONLY(_live_oops_index_at_perm = _live_oops_index);
310 CompactPoint perm_cp(pg, NULL, NULL);
311 pg->prepare_for_compaction(&perm_cp);
312 }
314 class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure {
315 public:
316 void do_generation(Generation* gen) {
317 gen->adjust_pointers();
318 }
319 };
321 void GenMarkSweep::mark_sweep_phase3(int level) {
322 GenCollectedHeap* gch = GenCollectedHeap::heap();
323 Generation* pg = gch->perm_gen();
325 // Adjust the pointers to reflect the new locations
326 EventMark m("3 adjust pointers");
327 TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);
328 trace("3");
330 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
332 // Needs to be done before the system dictionary is adjusted.
333 pg->pre_adjust_pointers();
335 // Because the two closures below are created statically, cannot
336 // use OopsInGenClosure constructor which takes a generation,
337 // as the Universe has not been created when the static constructors
338 // are run.
339 adjust_root_pointer_closure.set_orig_generation(gch->get_gen(level));
340 adjust_pointer_closure.set_orig_generation(gch->get_gen(level));
342 gch->gen_process_strong_roots(level,
343 false, // Younger gens are not roots.
344 true, // activate StrongRootsScope
345 true, // Collecting permanent generation.
346 SharedHeap::SO_AllClasses,
347 &adjust_root_pointer_closure,
348 false, // do not walk code
349 &adjust_root_pointer_closure);
351 // Now adjust pointers in remaining weak roots. (All of which should
352 // have been cleared if they pointed to non-surviving objects.)
353 CodeBlobToOopClosure adjust_code_pointer_closure(&adjust_pointer_closure,
354 /*do_marking=*/ false);
355 gch->gen_process_weak_roots(&adjust_root_pointer_closure,
356 &adjust_code_pointer_closure,
357 &adjust_pointer_closure);
359 adjust_marks();
360 GenAdjustPointersClosure blk;
361 gch->generation_iterate(&blk, true);
362 pg->adjust_pointers();
363 }
365 class GenCompactClosure: public GenCollectedHeap::GenClosure {
366 public:
367 void do_generation(Generation* gen) {
368 gen->compact();
369 }
370 };
372 void GenMarkSweep::mark_sweep_phase4() {
373 // All pointers are now adjusted, move objects accordingly
375 // It is imperative that we traverse perm_gen first in phase4. All
376 // classes must be allocated earlier than their instances, and traversing
377 // perm_gen first makes sure that all klassOops have moved to their new
378 // location before any instance does a dispatch through it's klass!
380 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
381 // in the same order in phase2, phase3 and phase4. We don't quite do that
382 // here (perm_gen first rather than last), so we tell the validate code
383 // to use a higher index (saved from phase2) when verifying perm_gen.
384 GenCollectedHeap* gch = GenCollectedHeap::heap();
385 Generation* pg = gch->perm_gen();
387 EventMark m("4 compact heap");
388 TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty);
389 trace("4");
391 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(true));
393 pg->compact();
395 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
397 GenCompactClosure blk;
398 gch->generation_iterate(&blk, true);
400 VALIDATE_MARK_SWEEP_ONLY(compaction_complete());
402 pg->post_compact(); // Shared spaces verification.
403 }