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/g1MarkSweep.hpp"
33 #include "gc/g1/g1RootProcessor.hpp"
34 #include "gc/g1/g1StringDedup.hpp"
35 #include "gc/serial/markSweep.inline.hpp"
36 #include "gc/shared/gcHeapSummary.hpp"
37 #include "gc/shared/gcLocker.hpp"
38 #include "gc/shared/gcTimer.hpp"
39 #include "gc/shared/gcTrace.hpp"
40 #include "gc/shared/gcTraceTime.inline.hpp"
41 #include "gc/shared/genCollectedHeap.hpp"
42 #include "gc/shared/modRefBarrierSet.hpp"
43 #include "gc/shared/referencePolicy.hpp"
44 #include "gc/shared/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 bool G1MarkSweep::_archive_check_enabled = false;
60 G1ArchiveRegionMap G1MarkSweep::_archive_region_map;
61
62 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
63 bool clear_all_softrefs) {
64 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
65
66 #ifdef ASSERT
67 if (G1CollectedHeap::heap()->collector_policy()->should_clear_all_soft_refs()) {
68 assert(clear_all_softrefs, "Policy should have been checked earler");
69 }
70 #endif
71 // hook up weak ref data so it can be used during Mark-Sweep
72 assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
73 assert(rp != NULL, "should be non-NULL");
74 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition");
75
76 GenMarkSweep::set_ref_processor(rp);
77 rp->setup_policy(clear_all_softrefs);
78
79 // When collecting the permanent generation Method*s may be moving,
80 // so we either have to flush all bcp data or convert it into bci.
81 CodeCache::gc_prologue();
82
83 bool marked_for_unloading = false;
84
85 allocate_stacks();
86
87 // We should save the marks of the currently locked biased monitors.
88 // The marking doesn't preserve the marks of biased objects.
89 BiasedLocking::preserve_marks();
90
91 mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
92
93 mark_sweep_phase2();
94
95 #if defined(COMPILER2) || INCLUDE_JVMCI
96 // Don't add any more derived pointers during phase3
97 DerivedPointerTable::set_active(false);
98 #endif
99
100 mark_sweep_phase3();
101
102 mark_sweep_phase4();
103
104 GenMarkSweep::restore_marks();
105 BiasedLocking::restore_marks();
106 GenMarkSweep::deallocate_stacks();
107
108 CodeCache::gc_epilogue();
109 JvmtiExport::gc_epilogue();
110
111 // refs processing: clean slate
112 GenMarkSweep::set_ref_processor(NULL);
113 }
114
115
116 void G1MarkSweep::allocate_stacks() {
117 GenMarkSweep::_preserved_count_max = 0;
118 GenMarkSweep::_preserved_marks = NULL;
119 GenMarkSweep::_preserved_count = 0;
120 }
121
122 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
123 bool clear_all_softrefs) {
124 // Recursively traverse all live objects and mark them
125 GCTraceTime(Trace, gc) tm("Phase 1: Mark live objects", gc_timer());
126
127 G1CollectedHeap* g1h = G1CollectedHeap::heap();
128
129 // Need cleared claim bits for the roots processing
130 ClassLoaderDataGraph::clear_claimed_marks();
131
132 MarkingCodeBlobClosure follow_code_closure(&GenMarkSweep::follow_root_closure, !CodeBlobToOopClosure::FixRelocations);
133 {
134 G1RootProcessor root_processor(g1h, 1);
135 root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure,
136 &GenMarkSweep::follow_cld_closure,
137 &follow_code_closure);
138 }
139
140 // Process reference objects found during marking
141 ReferenceProcessor* rp = GenMarkSweep::ref_processor();
142 assert(rp == g1h->ref_processor_stw(), "Sanity");
143
144 rp->setup_policy(clear_all_softrefs);
145 const ReferenceProcessorStats& stats =
146 rp->process_discovered_references(&GenMarkSweep::is_alive,
147 &GenMarkSweep::keep_alive,
148 &GenMarkSweep::follow_stack_closure,
149 NULL,
150 gc_timer());
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 {
158 GCTraceTime(Debug, gc) trace("Class Unloading", gc_timer());
159
160 // Unload classes and purge the SystemDictionary.
161 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
162
163 // Unload nmethods.
164 CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);
165
166 // Prune dead klasses from subklass/sibling/implementor lists.
167 Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);
168 }
169
170 {
171 GCTraceTime(Debug, gc) trace("Scrub String and Symbol Tables", gc_timer());
172 // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.
173 g1h->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);
174 }
175
176 if (G1StringDedup::is_enabled()) {
177 GCTraceTime(Debug, gc) trace("String Deduplication Unlink", gc_timer());
178 G1StringDedup::unlink(&GenMarkSweep::is_alive);
179 }
180
181 if (VerifyDuringGC) {
182 HandleMark hm; // handle scope
183 #if defined(COMPILER2) || INCLUDE_JVMCI
184 DerivedPointerTableDeactivate dpt_deact;
185 #endif
186 g1h->prepare_for_verify();
187 // Note: we can verify only the heap here. When an object is
188 // marked, the previous value of the mark word (including
189 // identity hash values, ages, etc) is preserved, and the mark
190 // word is set to markOop::marked_value - effectively removing
191 // any hash values from the mark word. These hash values are
192 // used when verifying the dictionaries and so removing them
193 // from the mark word can make verification of the dictionaries
194 // fail. At the end of the GC, the original mark word values
195 // (including hash values) are restored to the appropriate
196 // objects.
197 GCTraceTime(Info, gc, verify)("During GC (full)");
198 g1h->verify(VerifyOption_G1UseMarkWord);
199 }
200
201 gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
202 }
203
204
205 void G1MarkSweep::mark_sweep_phase2() {
206 // Now all live objects are marked, compute the new object addresses.
207
208 // It is not required that we traverse spaces in the same order in
209 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
210 // tracking expects us to do so. See comment under phase4.
211
212 GCTraceTime(Trace, gc) tm("Phase 2: Compute new object addresses", gc_timer());
213
214 prepare_compaction();
215 }
216
217 class G1AdjustPointersClosure: public HeapRegionClosure {
218 public:
219 bool doHeapRegion(HeapRegion* r) {
220 if (r->is_humongous()) {
221 if (r->is_starts_humongous()) {
222 // We must adjust the pointers on the single H object.
223 oop obj = oop(r->bottom());
224 // point all the oops to the new location
225 MarkSweep::adjust_pointers(obj);
226 }
227 } else if (!r->is_pinned()) {
228 // This really ought to be "as_CompactibleSpace"...
229 r->adjust_pointers();
230 }
231 return false;
232 }
233 };
234
235 void G1MarkSweep::mark_sweep_phase3() {
236 G1CollectedHeap* g1h = G1CollectedHeap::heap();
237
238 // Adjust the pointers to reflect the new locations
239 GCTraceTime(Trace, gc) tm("Phase 3: Adjust pointers", gc_timer());
240
241 // Need cleared claim bits for the roots processing
242 ClassLoaderDataGraph::clear_claimed_marks();
243
244 CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
245 {
246 G1RootProcessor root_processor(g1h, 1);
247 root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure,
248 &GenMarkSweep::adjust_cld_closure,
249 &adjust_code_closure);
250 }
251
252 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
253 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
254
255 // Now adjust pointers in remaining weak roots. (All of which should
256 // have been cleared if they pointed to non-surviving objects.)
257 JNIHandles::weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
258
259 if (G1StringDedup::is_enabled()) {
260 G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);
261 }
262
263 GenMarkSweep::adjust_marks();
264
265 G1AdjustPointersClosure blk;
266 g1h->heap_region_iterate(&blk);
267 }
268
269 class G1SpaceCompactClosure: public HeapRegionClosure {
270 public:
271 G1SpaceCompactClosure() {}
272
273 bool doHeapRegion(HeapRegion* hr) {
274 if (hr->is_humongous()) {
275 if (hr->is_starts_humongous()) {
276 oop obj = oop(hr->bottom());
277 if (obj->is_gc_marked()) {
278 obj->init_mark();
279 } else {
280 assert(hr->is_empty(), "Should have been cleared in phase 2.");
281 }
282 }
283 hr->reset_during_compaction();
284 } else if (!hr->is_pinned()) {
285 hr->compact();
286 }
287 return false;
288 }
289 };
290
291 void G1MarkSweep::mark_sweep_phase4() {
292 // All pointers are now adjusted, move objects accordingly
293
294 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
295 // in the same order in phase2, phase3 and phase4. We don't quite do that
296 // here (code and comment not fixed for perm removal), so we tell the validate code
297 // to use a higher index (saved from phase2) when verifying perm_gen.
298 G1CollectedHeap* g1h = G1CollectedHeap::heap();
299
300 GCTraceTime(Trace, gc) tm("Phase 4: Move objects", gc_timer());
301
302 G1SpaceCompactClosure blk;
303 g1h->heap_region_iterate(&blk);
304
305 }
306
307 void G1MarkSweep::enable_archive_object_check() {
308 assert(!_archive_check_enabled, "archive range check already enabled");
309 _archive_check_enabled = true;
310 size_t length = Universe::heap()->max_capacity();
311 _archive_region_map.initialize((HeapWord*)Universe::heap()->base(),
312 (HeapWord*)Universe::heap()->base() + length,
313 HeapRegion::GrainBytes);
314 }
315
316 void G1MarkSweep::set_range_archive(MemRegion range, bool is_archive) {
317 assert(_archive_check_enabled, "archive range check not enabled");
318 _archive_region_map.set_by_address(range, is_archive);
319 }
320
321 bool G1MarkSweep::in_archive_range(oop object) {
322 // This is the out-of-line part of is_archive_object test, done separately
323 // to avoid additional performance impact when the check is not enabled.
324 return _archive_region_map.get_by_address((HeapWord*)object);
325 }
326
327 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) {
328 G1CollectedHeap* g1h = G1CollectedHeap::heap();
329 g1h->heap_region_iterate(blk);
330 blk->update_sets();
331 }
332
333 void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) {
334 HeapWord* end = hr->end();
335 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
336
337 hr->set_containing_set(NULL);
338 _humongous_regions_removed++;
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 _g1h->remove_from_old_sets(0, _humongous_regions_removed);
368 }
369
370 bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) {
371 if (hr->is_humongous()) {
372 oop obj = oop(hr->humongous_start_region()->bottom());
373 if (hr->is_starts_humongous() && obj->is_gc_marked()) {
374 obj->forward_to(obj);
375 }
376 if (!obj->is_gc_marked()) {
377 free_humongous_region(hr);
378 }
379 } else if (!hr->is_pinned()) {
380 prepare_for_compaction(hr, hr->end());
381 }
382 return false;
383 }