1 /*
2 * Copyright (c) 2001, 2018, 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/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/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 Threads::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 Threads::gc_epilogue();
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 if (ClassUnloading) {
139 root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure,
140 &GenMarkSweep::follow_cld_closure,
141 &follow_code_closure);
142 } else {
143 root_processor.process_all_roots_no_string_table(
144 &GenMarkSweep::follow_root_closure,
145 &GenMarkSweep::follow_cld_closure,
146 &follow_code_closure);
147 }
148 }
149
150 // Process reference objects found during marking
151 ReferenceProcessor* rp = GenMarkSweep::ref_processor();
152 assert(rp == g1h->ref_processor_stw(), "Sanity");
153
154 rp->setup_policy(clear_all_softrefs);
155 const ReferenceProcessorStats& stats =
156 rp->process_discovered_references(&GenMarkSweep::is_alive,
157 &GenMarkSweep::keep_alive,
158 &GenMarkSweep::follow_stack_closure,
159 NULL,
160 gc_timer(),
161 gc_tracer()->gc_id());
162 gc_tracer()->report_gc_reference_stats(stats);
163
164
165 // This is the point where the entire marking should have completed.
166 assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
167
168 if (ClassUnloading) {
169
170 // Unload classes and purge the SystemDictionary.
171 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
172
173 // Unload nmethods.
174 CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);
175
176 // Prune dead klasses from subklass/sibling/implementor lists.
177 Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);
178 }
179 // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.
180 G1CollectedHeap::heap()->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);
181
182 if (VerifyDuringGC) {
183 HandleMark hm; // handle scope
184 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);
185 Universe::heap()->prepare_for_verify();
186 // Note: we can verify only the heap here. When an object is
187 // marked, the previous value of the mark word (including
188 // identity hash values, ages, etc) is preserved, and the mark
189 // word is set to markOop::marked_value - effectively removing
190 // any hash values from the mark word. These hash values are
191 // used when verifying the dictionaries and so removing them
192 // from the mark word can make verification of the dictionaries
193 // fail. At the end of the GC, the orginal mark word values
194 // (including hash values) are restored to the appropriate
195 // objects.
196 if (!VerifySilently) {
197 gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying ");
198 }
199 Universe::heap()->verify(VerifySilently, VerifyOption_G1UseMarkWord);
200 if (!VerifySilently) {
201 gclog_or_tty->print_cr("]");
202 }
203 }
204
205 gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
206 }
207
208
209 void G1MarkSweep::mark_sweep_phase2() {
210 // Now all live objects are marked, compute the new object addresses.
211
212 // It is not required that we traverse spaces in the same order in
213 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
214 // tracking expects us to do so. See comment under phase4.
215
216 GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
217 GenMarkSweep::trace("2");
218
219 prepare_compaction();
220 }
221
222 class G1AdjustPointersClosure: public HeapRegionClosure {
223 public:
224 bool doHeapRegion(HeapRegion* r) {
225 if (r->isHumongous()) {
226 if (r->startsHumongous()) {
227 // We must adjust the pointers on the single H object.
228 oop obj = oop(r->bottom());
229 // point all the oops to the new location
230 obj->adjust_pointers();
231 }
232 } else {
233 // This really ought to be "as_CompactibleSpace"...
234 r->adjust_pointers();
235 }
236 return false;
237 }
238 };
239
240 class G1AlwaysTrueClosure: public BoolObjectClosure {
241 public:
242 bool do_object_b(oop p) { return true; }
243 };
244 static G1AlwaysTrueClosure always_true;
245
246 void G1MarkSweep::mark_sweep_phase3() {
247 G1CollectedHeap* g1h = G1CollectedHeap::heap();
248
249 // Adjust the pointers to reflect the new locations
250 GCTraceTime tm("phase 3", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
251 GenMarkSweep::trace("3");
252
253 // Need cleared claim bits for the roots processing
254 ClassLoaderDataGraph::clear_claimed_marks();
255
256 CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
257 {
258 G1RootProcessor root_processor(g1h);
259 root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure,
260 &GenMarkSweep::adjust_cld_closure,
261 &adjust_code_closure);
262 }
263
264 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
265 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
266
267 // Now adjust pointers in remaining weak roots. (All of which should
268 // have been cleared if they pointed to non-surviving objects.)
269 JNIHandles::weak_oops_do(&always_true, &GenMarkSweep::adjust_pointer_closure);
270
271 if (G1StringDedup::is_enabled()) {
272 G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);
273 }
274
275 GenMarkSweep::adjust_marks();
276
277 G1AdjustPointersClosure blk;
278 g1h->heap_region_iterate(&blk);
279 }
280
281 class G1SpaceCompactClosure: public HeapRegionClosure {
282 public:
283 G1SpaceCompactClosure() {}
284
285 bool doHeapRegion(HeapRegion* hr) {
286 if (hr->isHumongous()) {
287 if (hr->startsHumongous()) {
288 oop obj = oop(hr->bottom());
289 if (obj->is_gc_marked()) {
290 obj->init_mark();
291 } else {
292 assert(hr->is_empty(), "Should have been cleared in phase 2.");
293 }
294 hr->reset_during_compaction();
295 }
296 } else {
297 hr->compact();
298 }
299 return false;
300 }
301 };
302
303 void G1MarkSweep::mark_sweep_phase4() {
304 // All pointers are now adjusted, move objects accordingly
305
306 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
307 // in the same order in phase2, phase3 and phase4. We don't quite do that
308 // here (code and comment not fixed for perm removal), so we tell the validate code
309 // to use a higher index (saved from phase2) when verifying perm_gen.
310 G1CollectedHeap* g1h = G1CollectedHeap::heap();
311
312 GCTraceTime tm("phase 4", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
313 GenMarkSweep::trace("4");
314
315 G1SpaceCompactClosure blk;
316 g1h->heap_region_iterate(&blk);
317
318 }
319
320 void G1MarkSweep::prepare_compaction_work(G1PrepareCompactClosure* blk) {
321 G1CollectedHeap* g1h = G1CollectedHeap::heap();
322 g1h->heap_region_iterate(blk);
323 blk->update_sets();
324 }
325
326 void G1PrepareCompactClosure::free_humongous_region(HeapRegion* hr) {
327 HeapWord* end = hr->end();
328 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
329
330 assert(hr->startsHumongous(),
331 "Only the start of a humongous region should be freed.");
332
333 hr->set_containing_set(NULL);
334 _humongous_regions_removed.increment(1u, hr->capacity());
335
336 _g1h->free_humongous_region(hr, &dummy_free_list, false /* par */);
337 prepare_for_compaction(hr, end);
338 dummy_free_list.remove_all();
339 }
340
341 void G1PrepareCompactClosure::prepare_for_compaction(HeapRegion* hr, HeapWord* end) {
342 // If this is the first live region that we came across which we can compact,
343 // initialize the CompactPoint.
344 if (!is_cp_initialized()) {
345 _cp.space = hr;
346 _cp.threshold = hr->initialize_threshold();
347 }
348 prepare_for_compaction_work(&_cp, hr, end);
349 }
350
351 void G1PrepareCompactClosure::prepare_for_compaction_work(CompactPoint* cp,
352 HeapRegion* hr,
353 HeapWord* end) {
354 hr->prepare_for_compaction(cp);
355 // Also clear the part of the card table that will be unused after
356 // compaction.
357 _mrbs->clear(MemRegion(hr->compaction_top(), end));
358 }
359
360 void G1PrepareCompactClosure::update_sets() {
361 // We'll recalculate total used bytes and recreate the free list
362 // at the end of the GC, so no point in updating those values here.
363 HeapRegionSetCount empty_set;
364 _g1h->remove_from_old_sets(empty_set, _humongous_regions_removed);
365 }
366
367 bool G1PrepareCompactClosure::doHeapRegion(HeapRegion* hr) {
368 if (hr->isHumongous()) {
369 if (hr->startsHumongous()) {
370 oop obj = oop(hr->bottom());
371 if (obj->is_gc_marked()) {
372 obj->forward_to(obj);
373 } else {
374 free_humongous_region(hr);
375 }
376 } else {
377 assert(hr->continuesHumongous(), "Invalid humongous.");
378 }
379 } else {
380 prepare_for_compaction(hr, hr->end());
381 }
382 return false;
383 }