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