1 /*
2 * Copyright (c) 2001, 2014, 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/g1/g1CollectedHeap.inline.hpp"
33 #include "gc_implementation/g1/g1Log.hpp"
34 #include "gc_implementation/g1/g1MarkSweep.hpp"
35 #include "gc_implementation/g1/g1StringDedup.hpp"
36 #include "gc_implementation/shared/gcHeapSummary.hpp"
37 #include "gc_implementation/shared/gcTimer.hpp"
38 #include "gc_implementation/shared/gcTrace.hpp"
39 #include "gc_implementation/shared/gcTraceTime.hpp"
40 #include "memory/gcLocker.hpp"
41 #include "memory/genCollectedHeap.hpp"
42 #include "memory/modRefBarrierSet.hpp"
43 #include "memory/referencePolicy.hpp"
44 #include "memory/space.hpp"
45 #include "oops/instanceRefKlass.hpp"
46 #include "oops/oop.inline.hpp"
47 #include "prims/jvmtiExport.hpp"
48 #include "runtime/atomic.inline.hpp"
49 #include "runtime/biasedLocking.hpp"
50 #include "runtime/fprofiler.hpp"
51 #include "runtime/synchronizer.hpp"
52 #include "runtime/thread.hpp"
53 #include "runtime/vmThread.hpp"
54 #include "utilities/copy.hpp"
55 #include "utilities/events.hpp"
56
57 class HeapRegion;
58
59 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
60 bool clear_all_softrefs) {
61 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
62
63 SharedHeap* sh = SharedHeap::heap();
64 #ifdef ASSERT
65 if (sh->collector_policy()->should_clear_all_soft_refs()) {
66 assert(clear_all_softrefs, "Policy should have been checked earler");
67 }
68 #endif
69 // hook up weak ref data so it can be used during Mark-Sweep
70 assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
71 assert(rp != NULL, "should be non-NULL");
72 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition");
73
74 GenMarkSweep::_ref_processor = rp;
75 rp->setup_policy(clear_all_softrefs);
76
77 // When collecting the permanent generation Method*s may be moving,
78 // so we either have to flush all bcp data or convert it into bci.
79 CodeCache::gc_prologue();
80
81 bool marked_for_unloading = false;
82
83 allocate_stacks();
84
85 // We should save the marks of the currently locked biased monitors.
86 // The marking doesn't preserve the marks of biased objects.
87 BiasedLocking::preserve_marks();
88
89 mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
90
91 mark_sweep_phase2();
92
93 // Don't add any more derived pointers during phase3
94 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
95
96 mark_sweep_phase3();
97
98 mark_sweep_phase4();
99
100 GenMarkSweep::restore_marks();
101 BiasedLocking::restore_marks();
102 GenMarkSweep::deallocate_stacks();
103
104 // "free at last gc" is calculated from these.
105 // CHF: cheating for now!!!
106 // Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity());
107 // Universe::set_heap_used_at_last_gc(Universe::heap()->used());
108
109 CodeCache::gc_epilogue();
110 JvmtiExport::gc_epilogue();
111
112 // refs processing: clean slate
113 GenMarkSweep::_ref_processor = NULL;
114 }
115
116
117 void G1MarkSweep::allocate_stacks() {
118 GenMarkSweep::_preserved_count_max = 0;
119 GenMarkSweep::_preserved_marks = NULL;
120 GenMarkSweep::_preserved_count = 0;
121 }
122
123 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
124 bool clear_all_softrefs) {
125 // Recursively traverse all live objects and mark them
126 GCTraceTime tm("phase 1", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
127 GenMarkSweep::trace(" 1");
128
129 SharedHeap* sh = SharedHeap::heap();
130
131 // Need cleared claim bits for the roots processing
132 ClassLoaderDataGraph::clear_claimed_marks();
133
134 MarkingCodeBlobClosure follow_code_closure(&GenMarkSweep::follow_root_closure, !CodeBlobToOopClosure::FixRelocations);
135 sh->process_strong_roots(true, // activate StrongRootsScope
136 SharedHeap::SO_None,
137 &GenMarkSweep::follow_root_closure,
138 &GenMarkSweep::follow_cld_closure,
139 &follow_code_closure);
140
141 // Process reference objects found during marking
142 ReferenceProcessor* rp = GenMarkSweep::ref_processor();
143 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Sanity");
144
145 rp->setup_policy(clear_all_softrefs);
146 const ReferenceProcessorStats& stats =
147 rp->process_discovered_references(&GenMarkSweep::is_alive,
148 &GenMarkSweep::keep_alive,
149 &GenMarkSweep::follow_stack_closure,
150 NULL,
151 gc_timer(),
152 gc_tracer()->gc_id());
153 gc_tracer()->report_gc_reference_stats(stats);
154
155
156 // This is the point where the entire marking should have completed.
157 assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
158
159 // Unload classes and purge the SystemDictionary.
160 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
161
162 // Unload nmethods.
163 CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);
164
165 // Prune dead klasses from subklass/sibling/implementor lists.
166 Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);
167
168 // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.
169 G1CollectedHeap::heap()->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);
170
171 if (VerifyDuringGC) {
172 HandleMark hm; // handle scope
173 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);
174 Universe::heap()->prepare_for_verify();
175 // Note: we can verify only the heap here. When an object is
176 // marked, the previous value of the mark word (including
177 // identity hash values, ages, etc) is preserved, and the mark
178 // word is set to markOop::marked_value - effectively removing
179 // any hash values from the mark word. These hash values are
180 // used when verifying the dictionaries and so removing them
181 // from the mark word can make verification of the dictionaries
182 // fail. At the end of the GC, the original mark word values
183 // (including hash values) are restored to the appropriate
184 // objects.
185 if (!VerifySilently) {
186 gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying ");
187 }
188 Universe::heap()->verify(VerifySilently, VerifyOption_G1UseMarkWord);
189 if (!VerifySilently) {
190 gclog_or_tty->print_cr("]");
191 }
192 }
193
194 gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
195 }
196
197
198 void G1MarkSweep::mark_sweep_phase2() {
199 // Now all live objects are marked, compute the new object addresses.
200
201 // It is not required that we traverse spaces in the same order in
202 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
203 // tracking expects us to do so. See comment under phase4.
204
205 GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
206 GenMarkSweep::trace("2");
207
208 prepare_compaction();
209 }
210
211 class G1AdjustPointersClosure: public HeapRegionClosure {
212 public:
213 bool doHeapRegion(HeapRegion* r) {
214 if (r->is_humongous()) {
215 if (r->is_starts_humongous()) {
216 // We must adjust the pointers on the single H object.
217 oop obj = oop(r->bottom());
218 // point all the oops to the new location
219 obj->adjust_pointers();
220 }
221 } else {
222 // This really ought to be "as_CompactibleSpace"...
223 r->adjust_pointers();
224 }
225 return false;
226 }
227 };
228
229 void G1MarkSweep::mark_sweep_phase3() {
230 G1CollectedHeap* g1h = G1CollectedHeap::heap();
231
232 // Adjust the pointers to reflect the new locations
233 GCTraceTime tm("phase 3", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
234 GenMarkSweep::trace("3");
235
236 SharedHeap* sh = SharedHeap::heap();
237
238 // Need cleared claim bits for the roots processing
239 ClassLoaderDataGraph::clear_claimed_marks();
240
241 CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
242 sh->process_all_roots(true, // activate StrongRootsScope
243 SharedHeap::SO_AllCodeCache,
244 &GenMarkSweep::adjust_pointer_closure,
245 &GenMarkSweep::adjust_cld_closure,
246 &adjust_code_closure);
247
248 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
249 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
250
251 // Now adjust pointers in remaining weak roots. (All of which should
252 // have been cleared if they pointed to non-surviving objects.)
253 sh->process_weak_roots(&GenMarkSweep::adjust_pointer_closure);
254
255 if (G1StringDedup::is_enabled()) {
256 G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);
257 }
258
259 GenMarkSweep::adjust_marks();
260
261 G1AdjustPointersClosure blk;
262 g1h->heap_region_iterate(&blk);
263 }
264
265 class G1SpaceCompactClosure: public HeapRegionClosure {
266 public:
267 G1SpaceCompactClosure() {}
268
269 bool doHeapRegion(HeapRegion* hr) {
270 if (hr->is_humongous()) {
271 if (hr->is_starts_humongous()) {
272 oop obj = oop(hr->bottom());
273 if (obj->is_gc_marked()) {
274 obj->init_mark();
275 } else {
276 assert(hr->is_empty(), "Should have been cleared in phase 2.");
277 }
278 hr->reset_during_compaction();
279 }
280 } else {
281 hr->compact();
282 }
283 return false;
284 }
285 };
286
287 void G1MarkSweep::mark_sweep_phase4() {
288 // All pointers are now adjusted, move objects accordingly
289
290 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
291 // in the same order in phase2, phase3 and phase4. We don't quite do that
292 // here (code and comment not fixed for perm removal), so we tell the validate code
293 // to use a higher index (saved from phase2) when verifying perm_gen.
294 G1CollectedHeap* g1h = G1CollectedHeap::heap();
295
296 GCTraceTime tm("phase 4", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
297 GenMarkSweep::trace("4");
298
299 G1SpaceCompactClosure blk;
300 g1h->heap_region_iterate(&blk);
301
302 }
303
304 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) {
305 G1CollectedHeap* g1h = G1CollectedHeap::heap();
306 g1h->heap_region_iterate(blk);
307 blk->update_sets();
308 }
309
310 void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) {
311 HeapWord* end = hr->end();
312 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
313
314 assert(hr->is_starts_humongous(),
315 "Only the start of a humongous region should be freed.");
316
317 hr->set_containing_set(NULL);
318 _humongous_regions_removed.increment(1u, hr->capacity());
319
320 _g1h->free_humongous_region(hr, &dummy_free_list, false /* par */);
321 prepare_for_compaction(hr, end);
322 dummy_free_list.remove_all();
323 }
324
325 void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) {
326 // If this is the first live region that we came across which we can compact,
327 // initialize the CompactPoint.
328 if (!is_cp_initialized()) {
329 _cp.space = hr;
330 _cp.threshold = hr->initialize_threshold();
331 }
332 prepare_for_compaction_work(&_cp, hr, end);
333 }
334
335 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp,
336 HeapRegion* hr,
337 HeapWord* end) {
338 hr->prepare_for_compaction(cp);
339 // Also clear the part of the card table that will be unused after
340 // compaction.
341 _mrbs->clear(MemRegion(hr->compaction_top(), end));
342 }
343
344 void G1PrepareCompactClosure::update_sets() {
345 // We'll recalculate total used bytes and recreate the free list
346 // at the end of the GC, so no point in updating those values here.
347 HeapRegionSetCount empty_set;
348 _g1h->remove_from_old_sets(empty_set, _humongous_regions_removed);
349 }
350
351 bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) {
352 if (hr->is_humongous()) {
353 if (hr->is_starts_humongous()) {
354 oop obj = oop(hr->bottom());
355 if (obj->is_gc_marked()) {
356 obj->forward_to(obj);
357 } else {
358 free_humongous_region(hr);
359 }
360 } else {
361 assert(hr->is_continues_humongous(), "Invalid humongous.");
362 }
363 } else {
364 prepare_for_compaction(hr, hr->end());
365 }
366 return false;
367 }