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_interface/collectedHeap.inline.hpp"
33 #include "memory/genCollectedHeap.hpp"
34 #include "memory/genMarkSweep.hpp"
35 #include "memory/genOopClosures.inline.hpp"
36 #include "memory/generation.inline.hpp"
37 #include "memory/modRefBarrierSet.hpp"
38 #include "memory/referencePolicy.hpp"
39 #include "memory/space.hpp"
40 #include "oops/instanceRefKlass.hpp"
41 #include "oops/oop.inline.hpp"
42 #include "prims/jvmtiExport.hpp"
43 #include "runtime/fprofiler.hpp"
44 #include "runtime/handles.inline.hpp"
45 #include "runtime/synchronizer.hpp"
46 #include "runtime/vmThread.hpp"
47 #include "utilities/copy.hpp"
48 #include "utilities/events.hpp"
49 #ifdef TARGET_OS_FAMILY_linux
50 # include "thread_linux.inline.hpp"
51 #endif
52 #ifdef TARGET_OS_FAMILY_solaris
53 # include "thread_solaris.inline.hpp"
54 #endif
55 #ifdef TARGET_OS_FAMILY_windows
56 # include "thread_windows.inline.hpp"
57 #endif
58
59 void GenMarkSweep::invoke_at_safepoint(int level, ReferenceProcessor* rp,
60 bool clear_all_softrefs) {
61 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
62
63 GenCollectedHeap* gch = GenCollectedHeap::heap();
64 #ifdef ASSERT
65 if (gch->collector_policy()->should_clear_all_soft_refs()) {
66 assert(clear_all_softrefs, "Policy should have been checked earlier");
67 }
68 #endif
69
70 // hook up weak ref data so it can be used during Mark-Sweep
71 assert(ref_processor() == NULL, "no stomping");
72 assert(rp != NULL, "should be non-NULL");
73 _ref_processor = rp;
74 rp->setup_policy(clear_all_softrefs);
75
76 TraceTime t1("Full GC", PrintGC && !PrintGCDetails, true, gclog_or_tty);
77
78 // When collecting the permanent generation methodOops may be moving,
79 // so we either have to flush all bcp data or convert it into bci.
80 CodeCache::gc_prologue();
81 Threads::gc_prologue();
82
83 // Increment the invocation count for the permanent generation, since it is
84 // implicitly collected whenever we do a full mark sweep collection.
85 gch->perm_gen()->stat_record()->invocations++;
86
87 // Capture heap size before collection for printing.
88 size_t gch_prev_used = gch->used();
89
90 // Some of the card table updates below assume that the perm gen is
91 // also being collected.
92 assert(level == gch->n_gens() - 1,
93 "All generations are being collected, ergo perm gen too.");
94
95 // Capture used regions for each generation that will be
96 // subject to collection, so that card table adjustments can
97 // be made intelligently (see clear / invalidate further below).
98 gch->save_used_regions(level, true /* perm */);
99
100 allocate_stacks();
101
102 mark_sweep_phase1(level, clear_all_softrefs);
103
104 mark_sweep_phase2();
105
106 // Don't add any more derived pointers during phase3
107 COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
108 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
109
110 mark_sweep_phase3(level);
111
112 VALIDATE_MARK_SWEEP_ONLY(
113 if (ValidateMarkSweep) {
114 guarantee(_root_refs_stack->length() == 0, "should be empty by now");
115 }
116 )
117
118 mark_sweep_phase4();
119
120 VALIDATE_MARK_SWEEP_ONLY(
121 if (ValidateMarkSweep) {
122 guarantee(_live_oops->length() == _live_oops_moved_to->length(),
123 "should be the same size");
124 }
125 )
126
127 restore_marks();
128
129 // Set saved marks for allocation profiler (and other things? -- dld)
130 // (Should this be in general part?)
131 gch->save_marks();
132
133 deallocate_stacks();
134
135 // If compaction completely evacuated all generations younger than this
136 // one, then we can clear the card table. Otherwise, we must invalidate
137 // it (consider all cards dirty). In the future, we might consider doing
138 // compaction within generations only, and doing card-table sliding.
139 bool all_empty = true;
140 for (int i = 0; all_empty && i < level; i++) {
141 Generation* g = gch->get_gen(i);
142 all_empty = all_empty && gch->get_gen(i)->used() == 0;
143 }
144 GenRemSet* rs = gch->rem_set();
145 // Clear/invalidate below make use of the "prev_used_regions" saved earlier.
146 if (all_empty) {
147 // We've evacuated all generations below us.
148 Generation* g = gch->get_gen(level);
149 rs->clear_into_younger(g, true /* perm */);
150 } else {
151 // Invalidate the cards corresponding to the currently used
152 // region and clear those corresponding to the evacuated region
153 // of all generations just collected (i.e. level and younger).
154 rs->invalidate_or_clear(gch->get_gen(level),
155 true /* younger */,
156 true /* perm */);
157 }
158
159 Threads::gc_epilogue();
160 CodeCache::gc_epilogue();
161
162 if (PrintGC && !PrintGCDetails) {
163 gch->print_heap_change(gch_prev_used);
164 }
165
166 // refs processing: clean slate
167 _ref_processor = NULL;
168
169 // Update heap occupancy information which is used as
170 // input to soft ref clearing policy at the next gc.
171 Universe::update_heap_info_at_gc();
172
173 // Update time of last gc for all generations we collected
174 // (which curently is all the generations in the heap).
175 gch->update_time_of_last_gc(os::javaTimeMillis());
176 }
177
178 void GenMarkSweep::allocate_stacks() {
179 GenCollectedHeap* gch = GenCollectedHeap::heap();
180 // Scratch request on behalf of oldest generation; will do no
181 // allocation.
182 ScratchBlock* scratch = gch->gather_scratch(gch->_gens[gch->_n_gens-1], 0);
183
184 // $$$ To cut a corner, we'll only use the first scratch block, and then
185 // revert to malloc.
186 if (scratch != NULL) {
187 _preserved_count_max =
188 scratch->num_words * HeapWordSize / sizeof(PreservedMark);
189 } else {
190 _preserved_count_max = 0;
191 }
192
193 _preserved_marks = (PreservedMark*)scratch;
194 _preserved_count = 0;
195 _preserved_mark_stack = NULL;
196 _preserved_oop_stack = NULL;
197
198 _marking_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(4000, true);
199 _objarray_stack = new (ResourceObj::C_HEAP) GrowableArray<ObjArrayTask>(50, true);
200
201 int size = SystemDictionary::number_of_classes() * 2;
202 _revisit_klass_stack = new (ResourceObj::C_HEAP) GrowableArray<Klass*>(size, true);
203 // (#klass/k)^2 for k ~ 10 appears to be a better fit, but this will have to do for
204 // now until we have had a chance to investigate a more optimal setting.
205 _revisit_mdo_stack = new (ResourceObj::C_HEAP) GrowableArray<DataLayout*>(2*size, true);
206
207 #ifdef VALIDATE_MARK_SWEEP
208 if (ValidateMarkSweep) {
209 _root_refs_stack = new (ResourceObj::C_HEAP) GrowableArray<void*>(100, true);
210 _other_refs_stack = new (ResourceObj::C_HEAP) GrowableArray<void*>(100, true);
211 _adjusted_pointers = new (ResourceObj::C_HEAP) GrowableArray<void*>(100, true);
212 _live_oops = new (ResourceObj::C_HEAP) GrowableArray<oop>(100, true);
213 _live_oops_moved_to = new (ResourceObj::C_HEAP) GrowableArray<oop>(100, true);
214 _live_oops_size = new (ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
215 }
216 if (RecordMarkSweepCompaction) {
217 if (_cur_gc_live_oops == NULL) {
218 _cur_gc_live_oops = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
219 _cur_gc_live_oops_moved_to = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
220 _cur_gc_live_oops_size = new(ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
221 _last_gc_live_oops = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
222 _last_gc_live_oops_moved_to = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
223 _last_gc_live_oops_size = new(ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
224 } else {
225 _cur_gc_live_oops->clear();
226 _cur_gc_live_oops_moved_to->clear();
227 _cur_gc_live_oops_size->clear();
228 }
229 }
230 #endif
231 }
232
233
234 void GenMarkSweep::deallocate_stacks() {
235 if (!UseG1GC) {
236 GenCollectedHeap* gch = GenCollectedHeap::heap();
237 gch->release_scratch();
238 }
239
240 if (_preserved_oop_stack) {
241 delete _preserved_mark_stack;
242 _preserved_mark_stack = NULL;
243 delete _preserved_oop_stack;
244 _preserved_oop_stack = NULL;
245 }
246
247 delete _marking_stack;
248 delete _objarray_stack;
249 delete _revisit_klass_stack;
250 delete _revisit_mdo_stack;
251
252 #ifdef VALIDATE_MARK_SWEEP
253 if (ValidateMarkSweep) {
254 delete _root_refs_stack;
255 delete _other_refs_stack;
256 delete _adjusted_pointers;
257 delete _live_oops;
258 delete _live_oops_size;
259 delete _live_oops_moved_to;
260 _live_oops_index = 0;
261 _live_oops_index_at_perm = 0;
262 }
263 #endif
264 }
265
266 void GenMarkSweep::mark_sweep_phase1(int level,
267 bool clear_all_softrefs) {
268 // Recursively traverse all live objects and mark them
269 EventMark m("1 mark object");
270 TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
271 trace(" 1");
272
273 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
274
275 GenCollectedHeap* gch = GenCollectedHeap::heap();
276
277 // Because follow_root_closure is created statically, cannot
278 // use OopsInGenClosure constructor which takes a generation,
279 // as the Universe has not been created when the static constructors
280 // are run.
281 follow_root_closure.set_orig_generation(gch->get_gen(level));
282
283 gch->gen_process_strong_roots(level,
284 false, // Younger gens are not roots.
285 true, // activate StrongRootsScope
286 true, // Collecting permanent generation.
287 SharedHeap::SO_SystemClasses,
288 &follow_root_closure,
289 true, // walk code active on stacks
290 &follow_root_closure);
291
292 // Process reference objects found during marking
293 {
294 ref_processor()->setup_policy(clear_all_softrefs);
295 ref_processor()->process_discovered_references(
296 &is_alive, &keep_alive, &follow_stack_closure, NULL);
297 }
298
299 // Follow system dictionary roots and unload classes
300 bool purged_class = SystemDictionary::do_unloading(&is_alive);
301
302 // Follow code cache roots
303 CodeCache::do_unloading(&is_alive, &keep_alive, purged_class);
304 follow_stack(); // Flush marking stack
305
306 // Update subklass/sibling/implementor links of live klasses
307 follow_weak_klass_links();
308 assert(_marking_stack->is_empty(), "just drained");
309
310 // Visit memoized MDO's and clear any unmarked weak refs
311 follow_mdo_weak_refs();
312 assert(_marking_stack->is_empty(), "just drained");
313
314 // Visit symbol and interned string tables and delete unmarked oops
315 SymbolTable::unlink(&is_alive);
316 StringTable::unlink(&is_alive);
317
318 assert(_marking_stack->is_empty(), "stack should be empty by now");
319 }
320
321
322 void GenMarkSweep::mark_sweep_phase2() {
323 // Now all live objects are marked, compute the new object addresses.
324
325 // It is imperative that we traverse perm_gen LAST. If dead space is
326 // allowed a range of dead object may get overwritten by a dead int
327 // array. If perm_gen is not traversed last a klassOop may get
328 // overwritten. This is fine since it is dead, but if the class has dead
329 // instances we have to skip them, and in order to find their size we
330 // need the klassOop!
331 //
332 // It is not required that we traverse spaces in the same order in
333 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
334 // tracking expects us to do so. See comment under phase4.
335
336 GenCollectedHeap* gch = GenCollectedHeap::heap();
337 Generation* pg = gch->perm_gen();
338
339 EventMark m("2 compute new addresses");
340 TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);
341 trace("2");
342
343 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
344
345 gch->prepare_for_compaction();
346
347 VALIDATE_MARK_SWEEP_ONLY(_live_oops_index_at_perm = _live_oops_index);
348 CompactPoint perm_cp(pg, NULL, NULL);
349 pg->prepare_for_compaction(&perm_cp);
350 }
351
352 class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure {
353 public:
354 void do_generation(Generation* gen) {
355 gen->adjust_pointers();
356 }
357 };
358
359 void GenMarkSweep::mark_sweep_phase3(int level) {
360 GenCollectedHeap* gch = GenCollectedHeap::heap();
361 Generation* pg = gch->perm_gen();
362
363 // Adjust the pointers to reflect the new locations
364 EventMark m("3 adjust pointers");
365 TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);
366 trace("3");
367
368 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
369
370 // Needs to be done before the system dictionary is adjusted.
371 pg->pre_adjust_pointers();
372
373 // Because the two closures below are created statically, cannot
374 // use OopsInGenClosure constructor which takes a generation,
375 // as the Universe has not been created when the static constructors
376 // are run.
377 adjust_root_pointer_closure.set_orig_generation(gch->get_gen(level));
378 adjust_pointer_closure.set_orig_generation(gch->get_gen(level));
379
380 gch->gen_process_strong_roots(level,
381 false, // Younger gens are not roots.
382 true, // activate StrongRootsScope
383 true, // Collecting permanent generation.
384 SharedHeap::SO_AllClasses,
385 &adjust_root_pointer_closure,
386 false, // do not walk code
387 &adjust_root_pointer_closure);
388
389 // Now adjust pointers in remaining weak roots. (All of which should
390 // have been cleared if they pointed to non-surviving objects.)
391 CodeBlobToOopClosure adjust_code_pointer_closure(&adjust_pointer_closure,
392 /*do_marking=*/ false);
393 gch->gen_process_weak_roots(&adjust_root_pointer_closure,
394 &adjust_code_pointer_closure,
395 &adjust_pointer_closure);
396
397 adjust_marks();
398 GenAdjustPointersClosure blk;
399 gch->generation_iterate(&blk, true);
400 pg->adjust_pointers();
401 }
402
403 class GenCompactClosure: public GenCollectedHeap::GenClosure {
404 public:
405 void do_generation(Generation* gen) {
406 gen->compact();
407 }
408 };
409
410 void GenMarkSweep::mark_sweep_phase4() {
411 // All pointers are now adjusted, move objects accordingly
412
413 // It is imperative that we traverse perm_gen first in phase4. All
414 // classes must be allocated earlier than their instances, and traversing
415 // perm_gen first makes sure that all klassOops have moved to their new
416 // location before any instance does a dispatch through it's klass!
417
418 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
419 // in the same order in phase2, phase3 and phase4. We don't quite do that
420 // here (perm_gen first rather than last), so we tell the validate code
421 // to use a higher index (saved from phase2) when verifying perm_gen.
422 GenCollectedHeap* gch = GenCollectedHeap::heap();
423 Generation* pg = gch->perm_gen();
424
425 EventMark m("4 compact heap");
426 TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty);
427 trace("4");
428
429 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(true));
430
431 pg->compact();
432
433 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
434
435 GenCompactClosure blk;
436 gch->generation_iterate(&blk, true);
437
438 VALIDATE_MARK_SWEEP_ONLY(compaction_complete());
439
440 pg->post_compact(); // Shared spaces verification.
441 }