1 /*
2 * Copyright (c) 2001, 2011, 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 #ifdef TARGET_OS_FAMILY_bsd
59 # include "thread_bsd.inline.hpp"
60 #endif
61
62 void GenMarkSweep::invoke_at_safepoint(int level, ReferenceProcessor* rp,
63 bool clear_all_softrefs) {
64 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
65
66 GenCollectedHeap* gch = GenCollectedHeap::heap();
67 #ifdef ASSERT
68 if (gch->collector_policy()->should_clear_all_soft_refs()) {
69 assert(clear_all_softrefs, "Policy should have been checked earlier");
70 }
71 #endif
72
73 // hook up weak ref data so it can be used during Mark-Sweep
74 assert(ref_processor() == NULL, "no stomping");
75 assert(rp != NULL, "should be non-NULL");
76 _ref_processor = rp;
77 rp->setup_policy(clear_all_softrefs);
78
79 TraceTime t1("Full GC", PrintGC && !PrintGCDetails, true, gclog_or_tty);
80
81 // When collecting the permanent generation methodOops may be moving,
82 // so we either have to flush all bcp data or convert it into bci.
83 CodeCache::gc_prologue();
84 Threads::gc_prologue();
85
86 // Increment the invocation count for the permanent generation, since it is
87 // implicitly collected whenever we do a full mark sweep collection.
88 gch->perm_gen()->stat_record()->invocations++;
89
90 // Capture heap size before collection for printing.
91 size_t gch_prev_used = gch->used();
92
93 // Some of the card table updates below assume that the perm gen is
94 // also being collected.
95 assert(level == gch->n_gens() - 1,
96 "All generations are being collected, ergo perm gen too.");
97
98 // Capture used regions for each generation that will be
99 // subject to collection, so that card table adjustments can
100 // be made intelligently (see clear / invalidate further below).
101 gch->save_used_regions(level, true /* perm */);
102
103 allocate_stacks();
104
105 mark_sweep_phase1(level, clear_all_softrefs);
106
107 mark_sweep_phase2();
108
109 // Don't add any more derived pointers during phase3
110 COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
111 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
112
113 mark_sweep_phase3(level);
114
115 VALIDATE_MARK_SWEEP_ONLY(
116 if (ValidateMarkSweep) {
117 guarantee(_root_refs_stack->length() == 0, "should be empty by now");
118 }
119 )
120
121 mark_sweep_phase4();
122
123 VALIDATE_MARK_SWEEP_ONLY(
124 if (ValidateMarkSweep) {
125 guarantee(_live_oops->length() == _live_oops_moved_to->length(),
126 "should be the same size");
127 }
128 )
129
130 restore_marks();
131
132 // Set saved marks for allocation profiler (and other things? -- dld)
133 // (Should this be in general part?)
134 gch->save_marks();
135
136 deallocate_stacks();
137
138 // If compaction completely evacuated all generations younger than this
139 // one, then we can clear the card table. Otherwise, we must invalidate
140 // it (consider all cards dirty). In the future, we might consider doing
141 // compaction within generations only, and doing card-table sliding.
142 bool all_empty = true;
143 for (int i = 0; all_empty && i < level; i++) {
144 Generation* g = gch->get_gen(i);
145 all_empty = all_empty && gch->get_gen(i)->used() == 0;
146 }
147 GenRemSet* rs = gch->rem_set();
148 // Clear/invalidate below make use of the "prev_used_regions" saved earlier.
149 if (all_empty) {
150 // We've evacuated all generations below us.
151 Generation* g = gch->get_gen(level);
152 rs->clear_into_younger(g, true /* perm */);
153 } else {
154 // Invalidate the cards corresponding to the currently used
155 // region and clear those corresponding to the evacuated region
156 // of all generations just collected (i.e. level and younger).
157 rs->invalidate_or_clear(gch->get_gen(level),
158 true /* younger */,
159 true /* perm */);
160 }
161
162 Threads::gc_epilogue();
163 CodeCache::gc_epilogue();
164 JvmtiExport::gc_epilogue();
165
166 if (PrintGC && !PrintGCDetails) {
167 gch->print_heap_change(gch_prev_used);
168 }
169
170 // refs processing: clean slate
171 _ref_processor = NULL;
172
173 // Update heap occupancy information which is used as
174 // input to soft ref clearing policy at the next gc.
175 Universe::update_heap_info_at_gc();
176
177 // Update time of last gc for all generations we collected
178 // (which curently is all the generations in the heap).
179 gch->update_time_of_last_gc(os::javaTimeMillis());
180 }
181
182 void GenMarkSweep::allocate_stacks() {
183 GenCollectedHeap* gch = GenCollectedHeap::heap();
184 // Scratch request on behalf of oldest generation; will do no
185 // allocation.
186 ScratchBlock* scratch = gch->gather_scratch(gch->_gens[gch->_n_gens-1], 0);
187
188 // $$$ To cut a corner, we'll only use the first scratch block, and then
189 // revert to malloc.
190 if (scratch != NULL) {
191 _preserved_count_max =
192 scratch->num_words * HeapWordSize / sizeof(PreservedMark);
193 } else {
194 _preserved_count_max = 0;
195 }
196
197 _preserved_marks = (PreservedMark*)scratch;
198 _preserved_count = 0;
199
200 #ifdef VALIDATE_MARK_SWEEP
201 if (ValidateMarkSweep) {
202 _root_refs_stack = new (ResourceObj::C_HEAP) GrowableArray<void*>(100, true);
203 _other_refs_stack = new (ResourceObj::C_HEAP) GrowableArray<void*>(100, true);
204 _adjusted_pointers = new (ResourceObj::C_HEAP) GrowableArray<void*>(100, true);
205 _live_oops = new (ResourceObj::C_HEAP) GrowableArray<oop>(100, true);
206 _live_oops_moved_to = new (ResourceObj::C_HEAP) GrowableArray<oop>(100, true);
207 _live_oops_size = new (ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
208 }
209 if (RecordMarkSweepCompaction) {
210 if (_cur_gc_live_oops == NULL) {
211 _cur_gc_live_oops = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
212 _cur_gc_live_oops_moved_to = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
213 _cur_gc_live_oops_size = new(ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
214 _last_gc_live_oops = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
215 _last_gc_live_oops_moved_to = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
216 _last_gc_live_oops_size = new(ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
217 } else {
218 _cur_gc_live_oops->clear();
219 _cur_gc_live_oops_moved_to->clear();
220 _cur_gc_live_oops_size->clear();
221 }
222 }
223 #endif
224 }
225
226
227 void GenMarkSweep::deallocate_stacks() {
228 if (!UseG1GC) {
229 GenCollectedHeap* gch = GenCollectedHeap::heap();
230 gch->release_scratch();
231 }
232
233 _preserved_mark_stack.clear(true);
234 _preserved_oop_stack.clear(true);
235 _marking_stack.clear();
236 _objarray_stack.clear(true);
237 _revisit_klass_stack.clear(true);
238 _revisit_mdo_stack.clear(true);
239
240 #ifdef VALIDATE_MARK_SWEEP
241 if (ValidateMarkSweep) {
242 delete _root_refs_stack;
243 delete _other_refs_stack;
244 delete _adjusted_pointers;
245 delete _live_oops;
246 delete _live_oops_size;
247 delete _live_oops_moved_to;
248 _live_oops_index = 0;
249 _live_oops_index_at_perm = 0;
250 }
251 #endif
252 }
253
254 void GenMarkSweep::mark_sweep_phase1(int level,
255 bool clear_all_softrefs) {
256 // Recursively traverse all live objects and mark them
257 EventMark m("1 mark object");
258 TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
259 trace(" 1");
260
261 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
262
263 GenCollectedHeap* gch = GenCollectedHeap::heap();
264
265 // Because follow_root_closure is created statically, cannot
266 // use OopsInGenClosure constructor which takes a generation,
267 // as the Universe has not been created when the static constructors
268 // are run.
269 follow_root_closure.set_orig_generation(gch->get_gen(level));
270
271 gch->gen_process_strong_roots(level,
272 false, // Younger gens are not roots.
273 true, // activate StrongRootsScope
274 true, // Collecting permanent generation.
275 SharedHeap::SO_SystemClasses,
276 &follow_root_closure,
277 true, // walk code active on stacks
278 &follow_root_closure);
279
280 // Process reference objects found during marking
281 {
282 ref_processor()->setup_policy(clear_all_softrefs);
283 ref_processor()->process_discovered_references(
284 &is_alive, &keep_alive, &follow_stack_closure, NULL);
285 }
286
287 // Follow system dictionary roots and unload classes
288 bool purged_class = SystemDictionary::do_unloading(&is_alive);
289
290 // Follow code cache roots
291 CodeCache::do_unloading(&is_alive, &keep_alive, purged_class);
292 follow_stack(); // Flush marking stack
293
294 // Update subklass/sibling/implementor links of live klasses
295 follow_weak_klass_links();
296 assert(_marking_stack.is_empty(), "just drained");
297
298 // Visit memoized MDO's and clear any unmarked weak refs
299 follow_mdo_weak_refs();
300 assert(_marking_stack.is_empty(), "just drained");
301
302 // Visit interned string tables and delete unmarked oops
303 StringTable::unlink(&is_alive);
304 // Clean up unreferenced symbols in symbol table.
305 SymbolTable::unlink();
306
307 assert(_marking_stack.is_empty(), "stack should be empty by now");
308 }
309
310
311 void GenMarkSweep::mark_sweep_phase2() {
312 // Now all live objects are marked, compute the new object addresses.
313
314 // It is imperative that we traverse perm_gen LAST. If dead space is
315 // allowed a range of dead object may get overwritten by a dead int
316 // array. If perm_gen is not traversed last a klassOop may get
317 // overwritten. This is fine since it is dead, but if the class has dead
318 // instances we have to skip them, and in order to find their size we
319 // need the klassOop!
320 //
321 // It is not required that we traverse spaces in the same order in
322 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
323 // tracking expects us to do so. See comment under phase4.
324
325 GenCollectedHeap* gch = GenCollectedHeap::heap();
326 Generation* pg = gch->perm_gen();
327
328 EventMark m("2 compute new addresses");
329 TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);
330 trace("2");
331
332 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
333
334 gch->prepare_for_compaction();
335
336 VALIDATE_MARK_SWEEP_ONLY(_live_oops_index_at_perm = _live_oops_index);
337 CompactPoint perm_cp(pg, NULL, NULL);
338 pg->prepare_for_compaction(&perm_cp);
339 }
340
341 class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure {
342 public:
343 void do_generation(Generation* gen) {
344 gen->adjust_pointers();
345 }
346 };
347
348 void GenMarkSweep::mark_sweep_phase3(int level) {
349 GenCollectedHeap* gch = GenCollectedHeap::heap();
350 Generation* pg = gch->perm_gen();
351
352 // Adjust the pointers to reflect the new locations
353 EventMark m("3 adjust pointers");
354 TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);
355 trace("3");
356
357 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
358
359 // Needs to be done before the system dictionary is adjusted.
360 pg->pre_adjust_pointers();
361
362 // Because the two closures below are created statically, cannot
363 // use OopsInGenClosure constructor which takes a generation,
364 // as the Universe has not been created when the static constructors
365 // are run.
366 adjust_root_pointer_closure.set_orig_generation(gch->get_gen(level));
367 adjust_pointer_closure.set_orig_generation(gch->get_gen(level));
368
369 gch->gen_process_strong_roots(level,
370 false, // Younger gens are not roots.
371 true, // activate StrongRootsScope
372 true, // Collecting permanent generation.
373 SharedHeap::SO_AllClasses,
374 &adjust_root_pointer_closure,
375 false, // do not walk code
376 &adjust_root_pointer_closure);
377
378 // Now adjust pointers in remaining weak roots. (All of which should
379 // have been cleared if they pointed to non-surviving objects.)
380 CodeBlobToOopClosure adjust_code_pointer_closure(&adjust_pointer_closure,
381 /*do_marking=*/ false);
382 gch->gen_process_weak_roots(&adjust_root_pointer_closure,
383 &adjust_code_pointer_closure,
384 &adjust_pointer_closure);
385
386 adjust_marks();
387 GenAdjustPointersClosure blk;
388 gch->generation_iterate(&blk, true);
389 pg->adjust_pointers();
390 }
391
392 class GenCompactClosure: public GenCollectedHeap::GenClosure {
393 public:
394 void do_generation(Generation* gen) {
395 gen->compact();
396 }
397 };
398
399 void GenMarkSweep::mark_sweep_phase4() {
400 // All pointers are now adjusted, move objects accordingly
401
402 // It is imperative that we traverse perm_gen first in phase4. All
403 // classes must be allocated earlier than their instances, and traversing
404 // perm_gen first makes sure that all klassOops have moved to their new
405 // location before any instance does a dispatch through it's klass!
406
407 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
408 // in the same order in phase2, phase3 and phase4. We don't quite do that
409 // here (perm_gen first rather than last), so we tell the validate code
410 // to use a higher index (saved from phase2) when verifying perm_gen.
411 GenCollectedHeap* gch = GenCollectedHeap::heap();
412 Generation* pg = gch->perm_gen();
413
414 EventMark m("4 compact heap");
415 TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty);
416 trace("4");
417
418 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(true));
419
420 pg->compact();
421
422 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
423
424 GenCompactClosure blk;
425 gch->generation_iterate(&blk, true);
426
427 VALIDATE_MARK_SWEEP_ONLY(compaction_complete());
428
429 pg->post_compact(); // Shared spaces verification.
430 }