1 /*
2 * Copyright (c) 2001, 2015, 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/g1/g1Log.hpp"
33 #include "gc/g1/g1MarkSweep.hpp"
34 #include "gc/g1/g1RootProcessor.hpp"
35 #include "gc/g1/g1StringDedup.hpp"
36 #include "gc/serial/markSweep.inline.hpp"
37 #include "gc/shared/gcHeapSummary.hpp"
38 #include "gc/shared/gcLocker.hpp"
39 #include "gc/shared/gcTimer.hpp"
40 #include "gc/shared/gcTrace.hpp"
41 #include "gc/shared/gcTraceTime.hpp"
42 #include "gc/shared/genCollectedHeap.hpp"
43 #include "gc/shared/modRefBarrierSet.hpp"
44 #include "gc/shared/referencePolicy.hpp"
45 #include "gc/shared/space.hpp"
46 #include "oops/instanceRefKlass.hpp"
47 #include "oops/oop.inline.hpp"
48 #include "prims/jvmtiExport.hpp"
49 #include "runtime/atomic.inline.hpp"
50 #include "runtime/biasedLocking.hpp"
51 #include "runtime/fprofiler.hpp"
52 #include "runtime/synchronizer.hpp"
53 #include "runtime/thread.hpp"
54 #include "runtime/vmThread.hpp"
55 #include "utilities/copy.hpp"
56 #include "utilities/events.hpp"
57
58 class HeapRegion;
59
60 bool G1MarkSweep::_archive_check_enabled = false;
61 G1ArchiveRegionMap G1MarkSweep::_archive_region_map;
62
63 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
64 bool clear_all_softrefs) {
65 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
66
67 #ifdef ASSERT
68 if (G1CollectedHeap::heap()->collector_policy()->should_clear_all_soft_refs()) {
69 assert(clear_all_softrefs, "Policy should have been checked earler");
70 }
71 #endif
72 // hook up weak ref data so it can be used during Mark-Sweep
73 assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
74 assert(rp != NULL, "should be non-NULL");
75 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition");
76
77 GenMarkSweep::set_ref_processor(rp);
78 rp->setup_policy(clear_all_softrefs);
79
80 // When collecting the permanent generation Method*s may be moving,
81 // so we either have to flush all bcp data or convert it into bci.
82 CodeCache::gc_prologue();
83
84 bool marked_for_unloading = false;
85
86 allocate_stacks();
87
88 // We should save the marks of the currently locked biased monitors.
89 // The marking doesn't preserve the marks of biased objects.
90 BiasedLocking::preserve_marks();
91
92 mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
93
94 mark_sweep_phase2();
95
96 // Don't add any more derived pointers during phase3
97 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
98
99 mark_sweep_phase3();
100
101 mark_sweep_phase4();
102
103 GenMarkSweep::restore_marks();
104 BiasedLocking::restore_marks();
105 GenMarkSweep::deallocate_stacks();
106
107 CodeCache::gc_epilogue();
108 JvmtiExport::gc_epilogue();
109
110 // refs processing: clean slate
111 GenMarkSweep::set_ref_processor(NULL);
112 }
113
114
115 void G1MarkSweep::allocate_stacks() {
116 GenMarkSweep::_preserved_count_max = 0;
117 GenMarkSweep::_preserved_marks = NULL;
118 GenMarkSweep::_preserved_count = 0;
119 }
120
121 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
122 bool clear_all_softrefs) {
123 // Recursively traverse all live objects and mark them
124 GCTraceTime tm("phase 1", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
125
126 G1CollectedHeap* g1h = G1CollectedHeap::heap();
127
128 // Need cleared claim bits for the roots processing
129 ClassLoaderDataGraph::clear_claimed_marks();
130
131 MarkingCodeBlobClosure follow_code_closure(&GenMarkSweep::follow_root_closure, !CodeBlobToOopClosure::FixRelocations);
132 {
133 G1RootProcessor root_processor(g1h, 1);
134 root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure,
135 &GenMarkSweep::follow_cld_closure,
136 &follow_code_closure);
137 }
138
139 // Process reference objects found during marking
140 ReferenceProcessor* rp = GenMarkSweep::ref_processor();
141 assert(rp == g1h->ref_processor_stw(), "Sanity");
142
143 rp->setup_policy(clear_all_softrefs);
144 const ReferenceProcessorStats& stats =
145 rp->process_discovered_references(&GenMarkSweep::is_alive,
146 &GenMarkSweep::keep_alive,
147 &GenMarkSweep::follow_stack_closure,
148 NULL,
149 gc_timer(),
150 gc_tracer()->gc_id());
151 gc_tracer()->report_gc_reference_stats(stats);
152
153
154 // This is the point where the entire marking should have completed.
155 assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
156
157 // Unload classes and purge the SystemDictionary.
158 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
159
160 // Unload nmethods.
161 CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);
162
163 // Prune dead klasses from subklass/sibling/implementor lists.
164 Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);
165
166 // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.
167 g1h->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);
168
169 if (VerifyDuringGC) {
170 HandleMark hm; // handle scope
171 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);
172 g1h->prepare_for_verify();
173 // Note: we can verify only the heap here. When an object is
174 // marked, the previous value of the mark word (including
175 // identity hash values, ages, etc) is preserved, and the mark
176 // word is set to markOop::marked_value - effectively removing
177 // any hash values from the mark word. These hash values are
178 // used when verifying the dictionaries and so removing them
179 // from the mark word can make verification of the dictionaries
180 // fail. At the end of the GC, the original mark word values
181 // (including hash values) are restored to the appropriate
182 // objects.
183 if (!VerifySilently) {
184 gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying ");
185 }
186 g1h->verify(VerifySilently, VerifyOption_G1UseMarkWord);
187 if (!VerifySilently) {
188 gclog_or_tty->print_cr("]");
189 }
190 }
191
192 gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
193 }
194
195
196 void G1MarkSweep::mark_sweep_phase2() {
197 // Now all live objects are marked, compute the new object addresses.
198
199 // It is not required that we traverse spaces in the same order in
200 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
201 // tracking expects us to do so. See comment under phase4.
202
203 GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
204
205 prepare_compaction();
206 }
207
208 class G1AdjustPointersClosure: public HeapRegionClosure {
209 public:
210 bool doHeapRegion(HeapRegion* r) {
211 if (r->is_humongous()) {
212 if (r->is_starts_humongous()) {
213 // We must adjust the pointers on the single H object.
214 oop obj = oop(r->bottom());
215 // point all the oops to the new location
216 MarkSweep::adjust_pointers(obj);
217 }
218 } else if (!r->is_pinned()) {
219 // This really ought to be "as_CompactibleSpace"...
220 r->adjust_pointers();
221 }
222 return false;
223 }
224 };
225
226 class G1AlwaysTrueClosure: public BoolObjectClosure {
227 public:
228 bool do_object_b(oop p) { return true; }
229 };
230 static G1AlwaysTrueClosure always_true;
231
232 void G1MarkSweep::mark_sweep_phase3() {
233 G1CollectedHeap* g1h = G1CollectedHeap::heap();
234
235 // Adjust the pointers to reflect the new locations
236 GCTraceTime tm("phase 3", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
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 {
243 G1RootProcessor root_processor(g1h, 1);
244 root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure,
245 &GenMarkSweep::adjust_cld_closure,
246 &adjust_code_closure);
247 }
248
249 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
250 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
251
252 // Now adjust pointers in remaining weak roots. (All of which should
253 // have been cleared if they pointed to non-surviving objects.)
254 JNIHandles::weak_oops_do(&always_true, &GenMarkSweep::adjust_pointer_closure);
255
256 if (G1StringDedup::is_enabled()) {
257 G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);
258 }
259
260 GenMarkSweep::adjust_marks();
261
262 G1AdjustPointersClosure blk;
263 g1h->heap_region_iterate(&blk);
264 }
265
266 class G1SpaceCompactClosure: public HeapRegionClosure {
267 public:
268 G1SpaceCompactClosure() {}
269
270 bool doHeapRegion(HeapRegion* hr) {
271 if (hr->is_humongous()) {
272 if (hr->is_starts_humongous()) {
273 oop obj = oop(hr->bottom());
274 if (obj->is_gc_marked()) {
275 obj->init_mark();
276 } else {
277 assert(hr->is_empty(), "Should have been cleared in phase 2.");
278 }
279 hr->reset_during_compaction();
280 }
281 } else if (!hr->is_pinned()) {
282 hr->compact();
283 }
284 return false;
285 }
286 };
287
288 void G1MarkSweep::mark_sweep_phase4() {
289 // All pointers are now adjusted, move objects accordingly
290
291 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
292 // in the same order in phase2, phase3 and phase4. We don't quite do that
293 // here (code and comment not fixed for perm removal), so we tell the validate code
294 // to use a higher index (saved from phase2) when verifying perm_gen.
295 G1CollectedHeap* g1h = G1CollectedHeap::heap();
296
297 GCTraceTime tm("phase 4", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
298
299 G1SpaceCompactClosure blk;
300 g1h->heap_region_iterate(&blk);
301
302 }
303
304 void G1MarkSweep::enable_archive_object_check() {
305 assert(!_archive_check_enabled, "archive range check already enabled");
306 _archive_check_enabled = true;
307 size_t length = Universe::heap()->max_capacity();
308 _archive_region_map.initialize((HeapWord*)Universe::heap()->base(),
309 (HeapWord*)Universe::heap()->base() + length,
310 HeapRegion::GrainBytes);
311 }
312
313 void G1MarkSweep::set_range_archive(MemRegion range, bool is_archive) {
314 assert(_archive_check_enabled, "archive range check not enabled");
315 _archive_region_map.set_by_address(range, is_archive);
316 }
317
318 bool G1MarkSweep::in_archive_range(oop object) {
319 // This is the out-of-line part of is_archive_object test, done separately
320 // to avoid additional performance impact when the check is not enabled.
321 return _archive_region_map.get_by_address((HeapWord*)object);
322 }
323
324 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) {
325 G1CollectedHeap* g1h = G1CollectedHeap::heap();
326 g1h->heap_region_iterate(blk);
327 blk->update_sets();
328 }
329
330 void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) {
331 HeapWord* end = hr->end();
332 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
333
334 assert(hr->is_starts_humongous(),
335 "Only the start of a humongous region should be freed.");
336
337 hr->set_containing_set(NULL);
338 _humongous_regions_removed.increment(1u, hr->capacity());
339
340 _g1h->free_humongous_region(hr, &dummy_free_list, false /* par */);
341 prepare_for_compaction(hr, end);
342 dummy_free_list.remove_all();
343 }
344
345 void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) {
346 // If this is the first live region that we came across which we can compact,
347 // initialize the CompactPoint.
348 if (!is_cp_initialized()) {
349 _cp.space = hr;
350 _cp.threshold = hr->initialize_threshold();
351 }
352 prepare_for_compaction_work(&_cp, hr, end);
353 }
354
355 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp,
356 HeapRegion* hr,
357 HeapWord* end) {
358 hr->prepare_for_compaction(cp);
359 // Also clear the part of the card table that will be unused after
360 // compaction.
361 _mrbs->clear(MemRegion(hr->compaction_top(), end));
362 }
363
364 void G1PrepareCompactClosure::update_sets() {
365 // We'll recalculate total used bytes and recreate the free list
366 // at the end of the GC, so no point in updating those values here.
367 HeapRegionSetCount empty_set;
368 _g1h->remove_from_old_sets(empty_set, _humongous_regions_removed);
369 }
370
371 bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) {
372 if (hr->is_humongous()) {
373 if (hr->is_starts_humongous()) {
374 oop obj = oop(hr->bottom());
375 if (obj->is_gc_marked()) {
376 obj->forward_to(obj);
377 } else {
378 free_humongous_region(hr);
379 }
380 } else {
381 assert(hr->is_continues_humongous(), "Invalid humongous.");
382 }
383 } else if (!hr->is_pinned()) {
384 prepare_for_compaction(hr, hr->end());
385 }
386 return false;
387 }