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_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 // We need to use a monotonically non-deccreasing time in ms
180 // or we will see time-warp warnings and os::javaTimeMillis()
181 // does not guarantee monotonicity.
182 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
183 gch->update_time_of_last_gc(now);
184 }
185
186 void GenMarkSweep::allocate_stacks() {
187 GenCollectedHeap* gch = GenCollectedHeap::heap();
188 // Scratch request on behalf of oldest generation; will do no
189 // allocation.
190 ScratchBlock* scratch = gch->gather_scratch(gch->_gens[gch->_n_gens-1], 0);
191
192 // $$$ To cut a corner, we'll only use the first scratch block, and then
193 // revert to malloc.
194 if (scratch != NULL) {
195 _preserved_count_max =
196 scratch->num_words * HeapWordSize / sizeof(PreservedMark);
197 } else {
198 _preserved_count_max = 0;
199 }
200
201 _preserved_marks = (PreservedMark*)scratch;
202 _preserved_count = 0;
203
204 #ifdef VALIDATE_MARK_SWEEP
205 if (ValidateMarkSweep) {
206 _root_refs_stack = new (ResourceObj::C_HEAP) GrowableArray<void*>(100, true);
207 _other_refs_stack = new (ResourceObj::C_HEAP) GrowableArray<void*>(100, true);
208 _adjusted_pointers = new (ResourceObj::C_HEAP) GrowableArray<void*>(100, true);
209 _live_oops = new (ResourceObj::C_HEAP) GrowableArray<oop>(100, true);
210 _live_oops_moved_to = new (ResourceObj::C_HEAP) GrowableArray<oop>(100, true);
211 _live_oops_size = new (ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
212 }
213 if (RecordMarkSweepCompaction) {
214 if (_cur_gc_live_oops == NULL) {
215 _cur_gc_live_oops = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
216 _cur_gc_live_oops_moved_to = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
217 _cur_gc_live_oops_size = new(ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
218 _last_gc_live_oops = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
219 _last_gc_live_oops_moved_to = new(ResourceObj::C_HEAP) GrowableArray<HeapWord*>(100, true);
220 _last_gc_live_oops_size = new(ResourceObj::C_HEAP) GrowableArray<size_t>(100, true);
221 } else {
222 _cur_gc_live_oops->clear();
223 _cur_gc_live_oops_moved_to->clear();
224 _cur_gc_live_oops_size->clear();
225 }
226 }
227 #endif
228 }
229
230
231 void GenMarkSweep::deallocate_stacks() {
232 if (!UseG1GC) {
233 GenCollectedHeap* gch = GenCollectedHeap::heap();
234 gch->release_scratch();
235 }
236
237 _preserved_mark_stack.clear(true);
238 _preserved_oop_stack.clear(true);
239 _marking_stack.clear();
240 _objarray_stack.clear(true);
241 _revisit_klass_stack.clear(true);
242 _revisit_mdo_stack.clear(true);
243
244 #ifdef VALIDATE_MARK_SWEEP
245 if (ValidateMarkSweep) {
246 delete _root_refs_stack;
247 delete _other_refs_stack;
248 delete _adjusted_pointers;
249 delete _live_oops;
250 delete _live_oops_size;
251 delete _live_oops_moved_to;
252 _live_oops_index = 0;
253 _live_oops_index_at_perm = 0;
254 }
255 #endif
256 }
257
258 void GenMarkSweep::mark_sweep_phase1(int level,
259 bool clear_all_softrefs) {
260 // Recursively traverse all live objects and mark them
261 TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
262 trace(" 1");
263
264 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
265
266 GenCollectedHeap* gch = GenCollectedHeap::heap();
267
268 // Because follow_root_closure is created statically, cannot
269 // use OopsInGenClosure constructor which takes a generation,
270 // as the Universe has not been created when the static constructors
271 // are run.
272 follow_root_closure.set_orig_generation(gch->get_gen(level));
273
274 gch->gen_process_strong_roots(level,
275 false, // Younger gens are not roots.
276 true, // activate StrongRootsScope
277 true, // Collecting permanent generation.
278 SharedHeap::SO_SystemClasses,
279 &follow_root_closure,
280 true, // walk code active on stacks
281 &follow_root_closure);
282
283 // Process reference objects found during marking
284 {
285 ref_processor()->setup_policy(clear_all_softrefs);
286 ref_processor()->process_discovered_references(
287 &is_alive, &keep_alive, &follow_stack_closure, NULL);
288 }
289
290 // Follow system dictionary roots and unload classes
291 bool purged_class = SystemDictionary::do_unloading(&is_alive);
292
293 // Follow code cache roots
294 CodeCache::do_unloading(&is_alive, &keep_alive, purged_class);
295 follow_stack(); // Flush marking stack
296
297 // Update subklass/sibling/implementor links of live klasses
298 follow_weak_klass_links();
299 assert(_marking_stack.is_empty(), "just drained");
300
301 // Visit memoized MDO's and clear any unmarked weak refs
302 follow_mdo_weak_refs();
303 assert(_marking_stack.is_empty(), "just drained");
304
305 // Visit interned string tables and delete unmarked oops
306 StringTable::unlink(&is_alive);
307 // Clean up unreferenced symbols in symbol table.
308 SymbolTable::unlink();
309
310 assert(_marking_stack.is_empty(), "stack should be empty by now");
311 }
312
313
314 void GenMarkSweep::mark_sweep_phase2() {
315 // Now all live objects are marked, compute the new object addresses.
316
317 // It is imperative that we traverse perm_gen LAST. If dead space is
318 // allowed a range of dead object may get overwritten by a dead int
319 // array. If perm_gen is not traversed last a klassOop may get
320 // overwritten. This is fine since it is dead, but if the class has dead
321 // instances we have to skip them, and in order to find their size we
322 // need the klassOop!
323 //
324 // It is not required that we traverse spaces in the same order in
325 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
326 // tracking expects us to do so. See comment under phase4.
327
328 GenCollectedHeap* gch = GenCollectedHeap::heap();
329 Generation* pg = gch->perm_gen();
330
331 TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);
332 trace("2");
333
334 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
335
336 gch->prepare_for_compaction();
337
338 VALIDATE_MARK_SWEEP_ONLY(_live_oops_index_at_perm = _live_oops_index);
339 CompactPoint perm_cp(pg, NULL, NULL);
340 pg->prepare_for_compaction(&perm_cp);
341 }
342
343 class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure {
344 public:
345 void do_generation(Generation* gen) {
346 gen->adjust_pointers();
347 }
348 };
349
350 void GenMarkSweep::mark_sweep_phase3(int level) {
351 GenCollectedHeap* gch = GenCollectedHeap::heap();
352 Generation* pg = gch->perm_gen();
353
354 // Adjust the pointers to reflect the new locations
355 TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);
356 trace("3");
357
358 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking(false));
359
360 // Needs to be done before the system dictionary is adjusted.
361 pg->pre_adjust_pointers();
362
363 // Because the two closures below are created statically, cannot
364 // use OopsInGenClosure constructor which takes a generation,
365 // as the Universe has not been created when the static constructors
366 // are run.
367 adjust_root_pointer_closure.set_orig_generation(gch->get_gen(level));
368 adjust_pointer_closure.set_orig_generation(gch->get_gen(level));
369
370 gch->gen_process_strong_roots(level,
371 false, // Younger gens are not roots.
372 true, // activate StrongRootsScope
373 true, // Collecting permanent generation.
374 SharedHeap::SO_AllClasses,
375 &adjust_root_pointer_closure,
376 false, // do not walk code
377 &adjust_root_pointer_closure);
378
379 // Now adjust pointers in remaining weak roots. (All of which should
380 // have been cleared if they pointed to non-surviving objects.)
381 CodeBlobToOopClosure adjust_code_pointer_closure(&adjust_pointer_closure,
382 /*do_marking=*/ false);
383 gch->gen_process_weak_roots(&adjust_root_pointer_closure,
384 &adjust_code_pointer_closure,
385 &adjust_pointer_closure);
386
387 adjust_marks();
388 GenAdjustPointersClosure blk;
389 gch->generation_iterate(&blk, true);
390 pg->adjust_pointers();
391 }
392
393 class GenCompactClosure: public GenCollectedHeap::GenClosure {
394 public:
395 void do_generation(Generation* gen) {
396 gen->compact();
397 }
398 };
399
400 void GenMarkSweep::mark_sweep_phase4() {
401 // All pointers are now adjusted, move objects accordingly
402
403 // It is imperative that we traverse perm_gen first in phase4. All
404 // classes must be allocated earlier than their instances, and traversing
405 // perm_gen first makes sure that all klassOops have moved to their new
406 // location before any instance does a dispatch through it's klass!
407
408 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
409 // in the same order in phase2, phase3 and phase4. We don't quite do that
410 // here (perm_gen first rather than last), so we tell the validate code
411 // to use a higher index (saved from phase2) when verifying perm_gen.
412 GenCollectedHeap* gch = GenCollectedHeap::heap();
413 Generation* pg = gch->perm_gen();
414
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 }