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_implementation/g1/g1Log.hpp"
33 #include "gc_implementation/g1/g1MarkSweep.hpp"
34 #include "gc_implementation/g1/g1RootProcessor.hpp"
35 #include "gc_implementation/g1/g1StringDedup.hpp"
36 #include "gc_implementation/shared/markSweep.inline.hpp"
37 #include "gc_implementation/shared/gcHeapSummary.hpp"
38 #include "gc_implementation/shared/gcTimer.hpp"
39 #include "gc_implementation/shared/gcTrace.hpp"
40 #include "gc_implementation/shared/gcTraceTime.hpp"
41 #include "memory/gcLocker.hpp"
42 #include "memory/genCollectedHeap.hpp"
43 #include "memory/modRefBarrierSet.hpp"
44 #include "memory/referencePolicy.hpp"
45 #include "memory/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 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
61 bool clear_all_softrefs) {
62 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
63
64 SharedHeap* sh = SharedHeap::heap();
65 #ifdef ASSERT
66 if (sh->collector_policy()->should_clear_all_soft_refs()) {
67 assert(clear_all_softrefs, "Policy should have been checked earler");
68 }
69 #endif
70 // hook up weak ref data so it can be used during Mark-Sweep
71 assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
72 assert(rp != NULL, "should be non-NULL");
73 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition");
74
75 GenMarkSweep::_ref_processor = rp;
76 rp->setup_policy(clear_all_softrefs);
77
78 // When collecting the permanent generation Method*s may be moving,
79 // so we either have to flush all bcp data or convert it into bci.
80 CodeCache::gc_prologue();
81
82 bool marked_for_unloading = false;
83
84 allocate_stacks();
85
86 // We should save the marks of the currently locked biased monitors.
87 // The marking doesn't preserve the marks of biased objects.
88 BiasedLocking::preserve_marks();
89
90 mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
91
92 mark_sweep_phase2();
93
94 // Don't add any more derived pointers during phase3
95 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
96
97 mark_sweep_phase3();
98
99 mark_sweep_phase4();
100
101 GenMarkSweep::restore_marks();
102 BiasedLocking::restore_marks();
103 GenMarkSweep::deallocate_stacks();
104
105 // "free at last gc" is calculated from these.
106 // CHF: cheating for now!!!
107 // Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity());
108 // Universe::set_heap_used_at_last_gc(Universe::heap()->used());
109
110 CodeCache::gc_epilogue();
111 JvmtiExport::gc_epilogue();
112
113 // refs processing: clean slate
114 GenMarkSweep::_ref_processor = NULL;
115 }
116
117
118 void G1MarkSweep::allocate_stacks() {
119 GenMarkSweep::_preserved_count_max = 0;
120 GenMarkSweep::_preserved_marks = NULL;
121 GenMarkSweep::_preserved_count = 0;
122 }
123
124 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
125 bool clear_all_softrefs) {
126 // Recursively traverse all live objects and mark them
127 GCTraceTime tm("phase 1", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
128 GenMarkSweep::trace(" 1");
129
130 G1CollectedHeap* g1h = G1CollectedHeap::heap();
131
132 // Need cleared claim bits for the roots processing
133 ClassLoaderDataGraph::clear_claimed_marks();
134
135 MarkingCodeBlobClosure follow_code_closure(&GenMarkSweep::follow_root_closure, !CodeBlobToOopClosure::FixRelocations);
136 {
137 G1RootProcessor root_processor(g1h);
138 root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure,
139 &GenMarkSweep::follow_cld_closure,
140 &follow_code_closure);
141 }
142
143 // Process reference objects found during marking
144 ReferenceProcessor* rp = GenMarkSweep::ref_processor();
145 assert(rp == g1h->ref_processor_stw(), "Sanity");
146
147 rp->setup_policy(clear_all_softrefs);
148 const ReferenceProcessorStats& stats =
149 rp->process_discovered_references(&GenMarkSweep::is_alive,
150 &GenMarkSweep::keep_alive,
151 &GenMarkSweep::follow_stack_closure,
152 NULL,
153 gc_timer(),
154 gc_tracer()->gc_id());
155 gc_tracer()->report_gc_reference_stats(stats);
156
157
158 // This is the point where the entire marking should have completed.
159 assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
160
161 // Unload classes and purge the SystemDictionary.
162 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
163
164 // Unload nmethods.
165 CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);
166
167 // Prune dead klasses from subklass/sibling/implementor lists.
168 Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);
169
170 // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.
171 G1CollectedHeap::heap()->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);
172
173 if (VerifyDuringGC) {
174 HandleMark hm; // handle scope
175 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);
176 Universe::heap()->prepare_for_verify();
177 // Note: we can verify only the heap here. When an object is
178 // marked, the previous value of the mark word (including
179 // identity hash values, ages, etc) is preserved, and the mark
180 // word is set to markOop::marked_value - effectively removing
181 // any hash values from the mark word. These hash values are
182 // used when verifying the dictionaries and so removing them
183 // from the mark word can make verification of the dictionaries
184 // fail. At the end of the GC, the original mark word values
185 // (including hash values) are restored to the appropriate
186 // objects.
187 if (!VerifySilently) {
188 gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying ");
189 }
190 Universe::heap()->verify(VerifySilently, VerifyOption_G1UseMarkWord);
191 if (!VerifySilently) {
192 gclog_or_tty->print_cr("]");
193 }
194 }
195
196 gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
197 }
198
199
200 void G1MarkSweep::mark_sweep_phase2() {
201 // Now all live objects are marked, compute the new object addresses.
202
203 // It is not required that we traverse spaces in the same order in
204 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
205 // tracking expects us to do so. See comment under phase4.
206
207 GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
208 GenMarkSweep::trace("2");
209
210 prepare_compaction();
211 }
212
213 class G1AdjustPointersClosure: public HeapRegionClosure {
214 public:
215 bool doHeapRegion(HeapRegion* r) {
216 if (r->is_humongous()) {
217 if (r->is_starts_humongous()) {
218 // We must adjust the pointers on the single H object.
219 oop obj = oop(r->bottom());
220 // point all the oops to the new location
221 MarkSweep::adjust_pointers(obj);
222 }
223 } else {
224 // This really ought to be "as_CompactibleSpace"...
225 r->adjust_pointers();
226 }
227 return false;
228 }
229 };
230
231 class G1AlwaysTrueClosure: public BoolObjectClosure {
232 public:
233 bool do_object_b(oop p) { return true; }
234 };
235 static G1AlwaysTrueClosure always_true;
236
237 void G1MarkSweep::mark_sweep_phase3() {
238 G1CollectedHeap* g1h = G1CollectedHeap::heap();
239
240 // Adjust the pointers to reflect the new locations
241 GCTraceTime tm("phase 3", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
242 GenMarkSweep::trace("3");
243
244 // Need cleared claim bits for the roots processing
245 ClassLoaderDataGraph::clear_claimed_marks();
246
247 CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
248 {
249 G1RootProcessor root_processor(g1h);
250 root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure,
251 &GenMarkSweep::adjust_cld_closure,
252 &adjust_code_closure);
253 }
254
255 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
256 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
257
258 // Now adjust pointers in remaining weak roots. (All of which should
259 // have been cleared if they pointed to non-surviving objects.)
260 JNIHandles::weak_oops_do(&always_true, &GenMarkSweep::adjust_pointer_closure);
261
262 if (G1StringDedup::is_enabled()) {
263 G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);
264 }
265
266 GenMarkSweep::adjust_marks();
267
268 G1AdjustPointersClosure blk;
269 g1h->heap_region_iterate(&blk);
270 }
271
272 class G1SpaceCompactClosure: public HeapRegionClosure {
273 public:
274 G1SpaceCompactClosure() {}
275
276 bool doHeapRegion(HeapRegion* hr) {
277 if (hr->is_humongous()) {
278 if (hr->is_starts_humongous()) {
279 oop obj = oop(hr->bottom());
280 if (obj->is_gc_marked()) {
281 obj->init_mark();
282 } else {
283 assert(hr->is_empty(), "Should have been cleared in phase 2.");
284 }
285 hr->reset_during_compaction();
286 }
287 } else {
288 hr->compact();
289 }
290 return false;
291 }
292 };
293
294 void G1MarkSweep::mark_sweep_phase4() {
295 // All pointers are now adjusted, move objects accordingly
296
297 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
298 // in the same order in phase2, phase3 and phase4. We don't quite do that
299 // here (code and comment not fixed for perm removal), so we tell the validate code
300 // to use a higher index (saved from phase2) when verifying perm_gen.
301 G1CollectedHeap* g1h = G1CollectedHeap::heap();
302
303 GCTraceTime tm("phase 4", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
304 GenMarkSweep::trace("4");
305
306 G1SpaceCompactClosure blk;
307 g1h->heap_region_iterate(&blk);
308
309 }
310
311 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) {
312 G1CollectedHeap* g1h = G1CollectedHeap::heap();
313 g1h->heap_region_iterate(blk);
314 blk->update_sets();
315 }
316
317 void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) {
318 HeapWord* end = hr->end();
319 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
320
321 assert(hr->is_starts_humongous(),
322 "Only the start of a humongous region should be freed.");
323
324 hr->set_containing_set(NULL);
325 _humongous_regions_removed.increment(1u, hr->capacity());
326
327 _g1h->free_humongous_region(hr, &dummy_free_list, false /* par */);
328 prepare_for_compaction(hr, end);
329 dummy_free_list.remove_all();
330 }
331
332 void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) {
333 // If this is the first live region that we came across which we can compact,
334 // initialize the CompactPoint.
335 if (!is_cp_initialized()) {
336 _cp.space = hr;
337 _cp.threshold = hr->initialize_threshold();
338 }
339 prepare_for_compaction_work(&_cp, hr, end);
340 }
341
342 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp,
343 HeapRegion* hr,
344 HeapWord* end) {
345 hr->prepare_for_compaction(cp);
346 // Also clear the part of the card table that will be unused after
347 // compaction.
348 _mrbs->clear(MemRegion(hr->compaction_top(), end));
349 }
350
351 void G1PrepareCompactClosure::update_sets() {
352 // We'll recalculate total used bytes and recreate the free list
353 // at the end of the GC, so no point in updating those values here.
354 HeapRegionSetCount empty_set;
355 _g1h->remove_from_old_sets(empty_set, _humongous_regions_removed);
356 }
357
358 bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) {
359 if (hr->is_humongous()) {
360 if (hr->is_starts_humongous()) {
361 oop obj = oop(hr->bottom());
362 if (obj->is_gc_marked()) {
363 obj->forward_to(obj);
364 } else {
365 free_humongous_region(hr);
366 }
367 } else {
368 assert(hr->is_continues_humongous(), "Invalid humongous.");
369 }
370 } else {
371 prepare_for_compaction(hr, hr->end());
372 }
373 return false;
374 }