Thu, 29 Nov 2012 11:23:15 -0800
Merge
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 */
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/thread.inline.hpp"
47 #include "runtime/vmThread.hpp"
48 #include "utilities/copy.hpp"
49 #include "utilities/events.hpp"
51 void GenMarkSweep::invoke_at_safepoint(int level, ReferenceProcessor* rp,
52 bool clear_all_softrefs) {
53 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
55 GenCollectedHeap* gch = GenCollectedHeap::heap();
56 #ifdef ASSERT
57 if (gch->collector_policy()->should_clear_all_soft_refs()) {
58 assert(clear_all_softrefs, "Policy should have been checked earlier");
59 }
60 #endif
62 // hook up weak ref data so it can be used during Mark-Sweep
63 assert(ref_processor() == NULL, "no stomping");
64 assert(rp != NULL, "should be non-NULL");
65 _ref_processor = rp;
66 rp->setup_policy(clear_all_softrefs);
68 TraceTime t1(GCCauseString("Full GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, gclog_or_tty);
70 // When collecting the permanent generation Method*s may be moving,
71 // so we either have to flush all bcp data or convert it into bci.
72 CodeCache::gc_prologue();
73 Threads::gc_prologue();
75 // Increment the invocation count
76 _total_invocations++;
78 // Capture heap size before collection for printing.
79 size_t gch_prev_used = gch->used();
81 // Some of the card table updates below assume that the perm gen is
82 // also being collected.
83 assert(level == gch->n_gens() - 1,
84 "All generations are being collected, ergo perm gen too.");
86 // Capture used regions for each generation that will be
87 // subject to collection, so that card table adjustments can
88 // be made intelligently (see clear / invalidate further below).
89 gch->save_used_regions(level);
91 allocate_stacks();
93 mark_sweep_phase1(level, clear_all_softrefs);
95 mark_sweep_phase2();
97 // Don't add any more derived pointers during phase3
98 COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
99 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
101 mark_sweep_phase3(level);
103 VALIDATE_MARK_SWEEP_ONLY(
104 if (ValidateMarkSweep) {
105 guarantee(_root_refs_stack->length() == 0, "should be empty by now");
106 }
107 )
109 mark_sweep_phase4();
111 VALIDATE_MARK_SWEEP_ONLY(
112 if (ValidateMarkSweep) {
113 guarantee(_live_oops->length() == _live_oops_moved_to->length(),
114 "should be the same size");
115 }
116 )
118 restore_marks();
120 // Set saved marks for allocation profiler (and other things? -- dld)
121 // (Should this be in general part?)
122 gch->save_marks();
124 deallocate_stacks();
126 // If compaction completely evacuated all generations younger than this
127 // one, then we can clear the card table. Otherwise, we must invalidate
128 // it (consider all cards dirty). In the future, we might consider doing
129 // compaction within generations only, and doing card-table sliding.
130 bool all_empty = true;
131 for (int i = 0; all_empty && i < level; i++) {
132 Generation* g = gch->get_gen(i);
133 all_empty = all_empty && gch->get_gen(i)->used() == 0;
134 }
135 GenRemSet* rs = gch->rem_set();
136 // Clear/invalidate below make use of the "prev_used_regions" saved earlier.
137 if (all_empty) {
138 // We've evacuated all generations below us.
139 Generation* g = gch->get_gen(level);
140 rs->clear_into_younger(g);
141 } else {
142 // Invalidate the cards corresponding to the currently used
143 // region and clear those corresponding to the evacuated region
144 // of all generations just collected (i.e. level and younger).
145 rs->invalidate_or_clear(gch->get_gen(level),
146 true /* younger */);
147 }
149 Threads::gc_epilogue();
150 CodeCache::gc_epilogue();
151 JvmtiExport::gc_epilogue();
153 if (PrintGC && !PrintGCDetails) {
154 gch->print_heap_change(gch_prev_used);
155 }
157 // refs processing: clean slate
158 _ref_processor = NULL;
160 // Update heap occupancy information which is used as
161 // input to soft ref clearing policy at the next gc.
162 Universe::update_heap_info_at_gc();
164 // Update time of last gc for all generations we collected
165 // (which curently is all the generations in the heap).
166 // We need to use a monotonically non-deccreasing time in ms
167 // or we will see time-warp warnings and os::javaTimeMillis()
168 // does not guarantee monotonicity.
169 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
170 gch->update_time_of_last_gc(now);
171 }
173 void GenMarkSweep::allocate_stacks() {
174 GenCollectedHeap* gch = GenCollectedHeap::heap();
175 // Scratch request on behalf of oldest generation; will do no
176 // allocation.
177 ScratchBlock* scratch = gch->gather_scratch(gch->_gens[gch->_n_gens-1], 0);
179 // $$$ To cut a corner, we'll only use the first scratch block, and then
180 // revert to malloc.
181 if (scratch != NULL) {
182 _preserved_count_max =
183 scratch->num_words * HeapWordSize / sizeof(PreservedMark);
184 } else {
185 _preserved_count_max = 0;
186 }
188 _preserved_marks = (PreservedMark*)scratch;
189 _preserved_count = 0;
191 #ifdef VALIDATE_MARK_SWEEP
192 if (ValidateMarkSweep) {
193 _root_refs_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<void*>(100, true);
194 _other_refs_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<void*>(100, true);
195 _adjusted_pointers = new (ResourceObj::C_HEAP, mtGC) GrowableArray<void*>(100, true);
196 _live_oops = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(100, true);
197 _live_oops_moved_to = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(100, true);
198 _live_oops_size = new (ResourceObj::C_HEAP, mtGC) GrowableArray<size_t>(100, true);
199 }
200 if (RecordMarkSweepCompaction) {
201 if (_cur_gc_live_oops == NULL) {
202 _cur_gc_live_oops = new(ResourceObj::C_HEAP, mtGC) GrowableArray<HeapWord*>(100, true);
203 _cur_gc_live_oops_moved_to = new(ResourceObj::C_HEAP, mtGC) GrowableArray<HeapWord*>(100, true);
204 _cur_gc_live_oops_size = new(ResourceObj::C_HEAP, mtGC) GrowableArray<size_t>(100, true);
205 _last_gc_live_oops = new(ResourceObj::C_HEAP, mtGC) GrowableArray<HeapWord*>(100, true);
206 _last_gc_live_oops_moved_to = new(ResourceObj::C_HEAP, mtGC) GrowableArray<HeapWord*>(100, true);
207 _last_gc_live_oops_size = new(ResourceObj::C_HEAP, mtGC) GrowableArray<size_t>(100, true);
208 } else {
209 _cur_gc_live_oops->clear();
210 _cur_gc_live_oops_moved_to->clear();
211 _cur_gc_live_oops_size->clear();
212 }
213 }
214 #endif
215 }
218 void GenMarkSweep::deallocate_stacks() {
219 if (!UseG1GC) {
220 GenCollectedHeap* gch = GenCollectedHeap::heap();
221 gch->release_scratch();
222 }
224 _preserved_mark_stack.clear(true);
225 _preserved_oop_stack.clear(true);
226 _marking_stack.clear();
227 _objarray_stack.clear(true);
229 #ifdef VALIDATE_MARK_SWEEP
230 if (ValidateMarkSweep) {
231 delete _root_refs_stack;
232 delete _other_refs_stack;
233 delete _adjusted_pointers;
234 delete _live_oops;
235 delete _live_oops_size;
236 delete _live_oops_moved_to;
237 _live_oops_index = 0;
238 _live_oops_index_at_perm = 0;
239 }
240 #endif
241 }
243 void GenMarkSweep::mark_sweep_phase1(int level,
244 bool clear_all_softrefs) {
245 // Recursively traverse all live objects and mark them
246 TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
247 trace(" 1");
249 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking());
251 GenCollectedHeap* gch = GenCollectedHeap::heap();
253 // Because follow_root_closure is created statically, cannot
254 // use OopsInGenClosure constructor which takes a generation,
255 // as the Universe has not been created when the static constructors
256 // are run.
257 follow_root_closure.set_orig_generation(gch->get_gen(level));
259 // Need new claim bits before marking starts.
260 ClassLoaderDataGraph::clear_claimed_marks();
262 gch->gen_process_strong_roots(level,
263 false, // Younger gens are not roots.
264 true, // activate StrongRootsScope
265 false, // not scavenging
266 SharedHeap::SO_SystemClasses,
267 &follow_root_closure,
268 true, // walk code active on stacks
269 &follow_root_closure,
270 &follow_klass_closure);
272 // Process reference objects found during marking
273 {
274 ref_processor()->setup_policy(clear_all_softrefs);
275 ref_processor()->process_discovered_references(
276 &is_alive, &keep_alive, &follow_stack_closure, NULL);
277 }
279 // Follow system dictionary roots and unload classes
280 bool purged_class = SystemDictionary::do_unloading(&is_alive);
282 // Follow code cache roots
283 CodeCache::do_unloading(&is_alive, purged_class);
284 follow_stack(); // Flush marking stack
286 // Update subklass/sibling/implementor links of live klasses
287 Klass::clean_weak_klass_links(&is_alive);
288 assert(_marking_stack.is_empty(), "just drained");
290 // Visit interned string tables and delete unmarked oops
291 StringTable::unlink(&is_alive);
292 // Clean up unreferenced symbols in symbol table.
293 SymbolTable::unlink();
295 assert(_marking_stack.is_empty(), "stack should be empty by now");
296 }
299 void GenMarkSweep::mark_sweep_phase2() {
300 // Now all live objects are marked, compute the new object addresses.
302 // It is imperative that we traverse perm_gen LAST. If dead space is
303 // allowed a range of dead object may get overwritten by a dead int
304 // array. If perm_gen is not traversed last a Klass* may get
305 // overwritten. This is fine since it is dead, but if the class has dead
306 // instances we have to skip them, and in order to find their size we
307 // need the Klass*!
308 //
309 // It is not required that we traverse spaces in the same order in
310 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
311 // tracking expects us to do so. See comment under phase4.
313 GenCollectedHeap* gch = GenCollectedHeap::heap();
315 TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);
316 trace("2");
318 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking());
320 gch->prepare_for_compaction();
321 }
323 class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure {
324 public:
325 void do_generation(Generation* gen) {
326 gen->adjust_pointers();
327 }
328 };
330 void GenMarkSweep::mark_sweep_phase3(int level) {
331 GenCollectedHeap* gch = GenCollectedHeap::heap();
333 // Adjust the pointers to reflect the new locations
334 TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);
335 trace("3");
337 // Need new claim bits for the pointer adjustment tracing.
338 ClassLoaderDataGraph::clear_claimed_marks();
340 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking());
342 // Because the two closures below are created statically, cannot
343 // use OopsInGenClosure constructor which takes a generation,
344 // as the Universe has not been created when the static constructors
345 // are run.
346 adjust_root_pointer_closure.set_orig_generation(gch->get_gen(level));
347 adjust_pointer_closure.set_orig_generation(gch->get_gen(level));
349 gch->gen_process_strong_roots(level,
350 false, // Younger gens are not roots.
351 true, // activate StrongRootsScope
352 false, // not scavenging
353 SharedHeap::SO_AllClasses,
354 &adjust_root_pointer_closure,
355 false, // do not walk code
356 &adjust_root_pointer_closure,
357 &adjust_klass_closure);
359 // Now adjust pointers in remaining weak roots. (All of which should
360 // have been cleared if they pointed to non-surviving objects.)
361 CodeBlobToOopClosure adjust_code_pointer_closure(&adjust_pointer_closure,
362 /*do_marking=*/ false);
363 gch->gen_process_weak_roots(&adjust_root_pointer_closure,
364 &adjust_code_pointer_closure,
365 &adjust_pointer_closure);
367 adjust_marks();
368 GenAdjustPointersClosure blk;
369 gch->generation_iterate(&blk, true);
370 }
372 class GenCompactClosure: public GenCollectedHeap::GenClosure {
373 public:
374 void do_generation(Generation* gen) {
375 gen->compact();
376 }
377 };
379 void GenMarkSweep::mark_sweep_phase4() {
380 // All pointers are now adjusted, move objects accordingly
382 // It is imperative that we traverse perm_gen first in phase4. All
383 // classes must be allocated earlier than their instances, and traversing
384 // perm_gen first makes sure that all Klass*s have moved to their new
385 // location before any instance does a dispatch through it's klass!
387 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
388 // in the same order in phase2, phase3 and phase4. We don't quite do that
389 // here (perm_gen first rather than last), so we tell the validate code
390 // to use a higher index (saved from phase2) when verifying perm_gen.
391 GenCollectedHeap* gch = GenCollectedHeap::heap();
393 TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty);
394 trace("4");
396 VALIDATE_MARK_SWEEP_ONLY(reset_live_oop_tracking());
398 GenCompactClosure blk;
399 gch->generation_iterate(&blk, true);
401 VALIDATE_MARK_SWEEP_ONLY(compaction_complete());
402 }