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(GCCauseString("Full GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, gclog_or_tty);
80
81 // When collecting the permanent generation Method*s 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
87 _total_invocations++;
88
89 // Capture heap size before collection for printing.
90 size_t gch_prev_used = gch->used();
91
92 // Some of the card table updates below assume that the perm gen is
93 // also being collected.
94 assert(level == gch->n_gens() - 1,
95 "All generations are being collected, ergo perm gen too.");
96
97 // Capture used regions for each generation that will be
98 // subject to collection, so that card table adjustments can
99 // be made intelligently (see clear / invalidate further below).
100 gch->save_used_regions(level);
101
102 allocate_stacks();
103
104 mark_sweep_phase1(level, clear_all_softrefs);
105
106 mark_sweep_phase2();
107
108 // Don't add any more derived pointers during phase3
109 COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
110 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
111
112 mark_sweep_phase3(level);
113
114 VALIDATE_MARK_SWEEP_ONLY(
115 if (ValidateMarkSweep) {
116 guarantee(_root_refs_stack->length() == 0, "should be empty by now");
117 }
118 )
119
120 mark_sweep_phase4();
121
122 VALIDATE_MARK_SWEEP_ONLY(
123 if (ValidateMarkSweep) {
124 guarantee(_live_oops->length() == _live_oops_moved_to->length(),
125 "should be the same size");
126 }
127 )
128
129 restore_marks();
130
131 // Set saved marks for allocation profiler (and other things? -- dld)
132 // (Should this be in general part?)
133 gch->save_marks();
134
135 deallocate_stacks();
136
137 // If compaction completely evacuated all generations younger than this
138 // one, then we can clear the card table. Otherwise, we must invalidate
139 // it (consider all cards dirty). In the future, we might consider doing
140 // compaction within generations only, and doing card-table sliding.
141 bool all_empty = true;
142 for (int i = 0; all_empty && i < level; i++) {
143 Generation* g = gch->get_gen(i);
144 all_empty = all_empty && gch->get_gen(i)->used() == 0;
145 }
146 GenRemSet* rs = gch->rem_set();
147 // Clear/invalidate below make use of the "prev_used_regions" saved earlier.
148 if (all_empty) {
149 // We've evacuated all generations below us.
150 Generation* g = gch->get_gen(level);
151 rs->clear_into_younger(g);
152 } else {
153 // Invalidate the cards corresponding to the currently used
154 // region and clear those corresponding to the evacuated region
155 // of all generations just collected (i.e. level and younger).
156 rs->invalidate_or_clear(gch->get_gen(level),
157 true /* younger */);
158 }
159
160 Threads::gc_epilogue();
161 CodeCache::gc_epilogue();
162 JvmtiExport::gc_epilogue();
163
164 if (PrintGC && !PrintGCDetails) {
165 gch->print_heap_change(gch_prev_used);
166 }
167
168 // refs processing: clean slate
169 _ref_processor = NULL;
170
171 // Update heap occupancy information which is used as
172 // input to soft ref clearing policy at the next gc.
173 Universe::update_heap_info_at_gc();
174
175 // Update time of last gc for all generations we collected
176 // (which curently is all the generations in the heap).
177 // We need to use a monotonically non-deccreasing time in ms
178 // or we will see time-warp warnings and os::javaTimeMillis()
179 // does not guarantee monotonicity.
180 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
181 gch->update_time_of_last_gc(now);
182 }
183
184 void GenMarkSweep::allocate_stacks() {
185 GenCollectedHeap* gch = GenCollectedHeap::heap();
186 // Scratch request on behalf of oldest generation; will do no
187 // allocation.
188 ScratchBlock* scratch = gch->gather_scratch(gch->_gens[gch->_n_gens-1], 0);
189
190 // $$$ To cut a corner, we'll only use the first scratch block, and then
191 // revert to malloc.
192 if (scratch != NULL) {
193 _preserved_count_max =
194 scratch->num_words * HeapWordSize / sizeof(PreservedMark);
195 } else {
196 _preserved_count_max = 0;
197 }
198
199 _preserved_marks = (PreservedMark*)scratch;
200 _preserved_count = 0;
201
202 #ifdef VALIDATE_MARK_SWEEP
203 if (ValidateMarkSweep) {
204 _root_refs_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<void*>(100, true);
205 _other_refs_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<void*>(100, true);
206 _adjusted_pointers = new (ResourceObj::C_HEAP, mtGC) GrowableArray<void*>(100, true);
207 _live_oops = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(100, true);
208 _live_oops_moved_to = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(100, true);
209 _live_oops_size = new (ResourceObj::C_HEAP, mtGC) GrowableArray<size_t>(100, true);
210 }
211 if (RecordMarkSweepCompaction) {
212 if (_cur_gc_live_oops == NULL) {
213 _cur_gc_live_oops = new(ResourceObj::C_HEAP, mtGC) GrowableArray<HeapWord*>(100, true);
214 _cur_gc_live_oops_moved_to = new(ResourceObj::C_HEAP, mtGC) GrowableArray<HeapWord*>(100, true);
215 _cur_gc_live_oops_size = new(ResourceObj::C_HEAP, mtGC) GrowableArray<size_t>(100, true);
216 _last_gc_live_oops = new(ResourceObj::C_HEAP, mtGC) GrowableArray<HeapWord*>(100, true);
217 _last_gc_live_oops_moved_to = new(ResourceObj::C_HEAP, mtGC) GrowableArray<HeapWord*>(100, true);
218 _last_gc_live_oops_size = new(ResourceObj::C_HEAP, mtGC) GrowableArray<size_t>(100, true);
219 } else {
220 _cur_gc_live_oops->clear();
221 _cur_gc_live_oops_moved_to->clear();
222 _cur_gc_live_oops_size->clear();
223 }
224 }
225 #endif
226 }
227
228
229 void GenMarkSweep::deallocate_stacks() {
230 if (!UseG1GC) {
231 GenCollectedHeap* gch = GenCollectedHeap::heap();
232 gch->release_scratch();
233 }
234
235 _preserved_mark_stack.clear(true);
236 _preserved_oop_stack.clear(true);
237 _marking_stack.clear();
238 _objarray_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 TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
258 trace(" 1");
259
260 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking());
261
262 GenCollectedHeap* gch = GenCollectedHeap::heap();
263
264 // Because follow_root_closure is created statically, cannot
265 // use OopsInGenClosure constructor which takes a generation,
266 // as the Universe has not been created when the static constructors
267 // are run.
268 follow_root_closure.set_orig_generation(gch->get_gen(level));
269
270 // Need new claim bits before marking starts.
271 ClassLoaderDataGraph::clear_claimed_marks();
272
273 gch->gen_process_strong_roots(level,
274 false, // Younger gens are not roots.
275 true, // activate StrongRootsScope
276 false, // not scavenging
277 SharedHeap::SO_SystemClasses,
278 &follow_root_closure,
279 true, // walk code active on stacks
280 &follow_root_closure,
281 &follow_klass_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, purged_class);
295 follow_stack(); // Flush marking stack
296
297 // Update subklass/sibling/implementor links of live klasses
298 Klass::clean_weak_klass_links(&is_alive);
299 assert(_marking_stack.is_empty(), "just drained");
300
301 // Visit interned string tables and delete unmarked oops
302 StringTable::unlink(&is_alive);
303 // Clean up unreferenced symbols in symbol table.
304 SymbolTable::unlink();
305
306 assert(_marking_stack.is_empty(), "stack should be empty by now");
307 }
308
309
310 void GenMarkSweep::mark_sweep_phase2() {
311 // Now all live objects are marked, compute the new object addresses.
312
313 // It is imperative that we traverse perm_gen LAST. If dead space is
314 // allowed a range of dead object may get overwritten by a dead int
315 // array. If perm_gen is not traversed last a Klass* may get
316 // overwritten. This is fine since it is dead, but if the class has dead
317 // instances we have to skip them, and in order to find their size we
318 // need the Klass*!
319 //
320 // It is not required that we traverse spaces in the same order in
321 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
322 // tracking expects us to do so. See comment under phase4.
323
324 GenCollectedHeap* gch = GenCollectedHeap::heap();
325
326 TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);
327 trace("2");
328
329 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking());
330
331 gch->prepare_for_compaction();
332 }
333
334 class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure {
335 public:
336 void do_generation(Generation* gen) {
337 gen->adjust_pointers();
338 }
339 };
340
341 void GenMarkSweep::mark_sweep_phase3(int level) {
342 GenCollectedHeap* gch = GenCollectedHeap::heap();
343
344 // Adjust the pointers to reflect the new locations
345 TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);
346 trace("3");
347
348 // Need new claim bits for the pointer adjustment tracing.
349 ClassLoaderDataGraph::clear_claimed_marks();
350
351 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking());
352
353 // Because the two closures below are created statically, cannot
354 // use OopsInGenClosure constructor which takes a generation,
355 // as the Universe has not been created when the static constructors
356 // are run.
357 adjust_root_pointer_closure.set_orig_generation(gch->get_gen(level));
358 adjust_pointer_closure.set_orig_generation(gch->get_gen(level));
359
360 gch->gen_process_strong_roots(level,
361 false, // Younger gens are not roots.
362 true, // activate StrongRootsScope
363 false, // not scavenging
364 SharedHeap::SO_AllClasses,
365 &adjust_root_pointer_closure,
366 false, // do not walk code
367 &adjust_root_pointer_closure,
368 &adjust_klass_closure);
369
370 // Now adjust pointers in remaining weak roots. (All of which should
371 // have been cleared if they pointed to non-surviving objects.)
372 CodeBlobToOopClosure adjust_code_pointer_closure(&adjust_pointer_closure,
373 /*do_marking=*/ false);
374 gch->gen_process_weak_roots(&adjust_root_pointer_closure,
375 &adjust_code_pointer_closure,
376 &adjust_pointer_closure);
377
378 adjust_marks();
379 GenAdjustPointersClosure blk;
380 gch->generation_iterate(&blk, true);
381 }
382
383 class GenCompactClosure: public GenCollectedHeap::GenClosure {
384 public:
385 void do_generation(Generation* gen) {
386 gen->compact();
387 }
388 };
389
390 void GenMarkSweep::mark_sweep_phase4() {
391 // All pointers are now adjusted, move objects accordingly
392
393 // It is imperative that we traverse perm_gen first in phase4. All
394 // classes must be allocated earlier than their instances, and traversing
395 // perm_gen first makes sure that all Klass*s have moved to their new
396 // location before any instance does a dispatch through it's klass!
397
398 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
399 // in the same order in phase2, phase3 and phase4. We don't quite do that
400 // here (perm_gen first rather than last), so we tell the validate code
401 // to use a higher index (saved from phase2) when verifying perm_gen.
402 GenCollectedHeap* gch = GenCollectedHeap::heap();
403
404 TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty);
405 trace("4");
406
407 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking());
408
409 GenCompactClosure blk;
410 gch->generation_iterate(&blk, true);
411
412 VALIDATE_MARK_SWEEP_ONLY(compaction_complete());
413 }