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