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 #if INCLUDE_JFR
56 #include "jfr/jfr.hpp"
57 #endif // INCLUDE_JFR
58
59 class HeapRegion;
60
61 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
62 bool clear_all_softrefs) {
63 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
64
65 SharedHeap* sh = SharedHeap::heap();
66 #ifdef ASSERT
67 if (sh->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::_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 Threads::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 // "free at last gc" is calculated from these.
108 // CHF: cheating for now!!!
109 // Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity());
110 // Universe::set_heap_used_at_last_gc(Universe::heap()->used());
111
112 Threads::gc_epilogue();
113 CodeCache::gc_epilogue();
114 JvmtiExport::gc_epilogue();
115
116 // refs processing: clean slate
117 GenMarkSweep::_ref_processor = NULL;
118 }
119
120
121 void G1MarkSweep::allocate_stacks() {
122 GenMarkSweep::_preserved_count_max = 0;
123 GenMarkSweep::_preserved_marks = NULL;
124 GenMarkSweep::_preserved_count = 0;
125 }
126
127 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
128 bool clear_all_softrefs) {
129 // Recursively traverse all live objects and mark them
130 GCTraceTime tm("phase 1", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
131 GenMarkSweep::trace(" 1");
132
133 G1CollectedHeap* g1h = G1CollectedHeap::heap();
134
135 // Need cleared claim bits for the roots processing
136 ClassLoaderDataGraph::clear_claimed_marks();
137
138 MarkingCodeBlobClosure follow_code_closure(&GenMarkSweep::follow_root_closure, !CodeBlobToOopClosure::FixRelocations);
139 {
140 G1RootProcessor root_processor(g1h);
141 if (ClassUnloading) {
142 root_processor.process_strong_roots(&GenMarkSweep::follow_root_closure,
143 &GenMarkSweep::follow_cld_closure,
144 &follow_code_closure);
145 } else {
146 root_processor.process_all_roots_no_string_table(
147 &GenMarkSweep::follow_root_closure,
148 &GenMarkSweep::follow_cld_closure,
149 &follow_code_closure);
150 }
151 }
152
153 // Process reference objects found during marking
154 ReferenceProcessor* rp = GenMarkSweep::ref_processor();
155 assert(rp == g1h->ref_processor_stw(), "Sanity");
156
157 rp->setup_policy(clear_all_softrefs);
158 const ReferenceProcessorStats& stats =
159 rp->process_discovered_references(&GenMarkSweep::is_alive,
160 &GenMarkSweep::keep_alive,
161 &GenMarkSweep::follow_stack_closure,
162 NULL,
163 gc_timer(),
164 gc_tracer()->gc_id());
165 gc_tracer()->report_gc_reference_stats(stats);
166
167
168 // This is the point where the entire marking should have completed.
169 assert(GenMarkSweep::_marking_stack.is_empty(), "Marking should have completed");
170
171 if (ClassUnloading) {
172
173 // Unload classes and purge the SystemDictionary.
174 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
175
176 // Unload nmethods.
177 CodeCache::do_unloading(&GenMarkSweep::is_alive, purged_class);
178
179 // Prune dead klasses from subklass/sibling/implementor lists.
180 Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);
181 }
182 // Delete entries for dead interned string and clean up unreferenced symbols in symbol table.
183 G1CollectedHeap::heap()->unlink_string_and_symbol_table(&GenMarkSweep::is_alive);
184
185 if (VerifyDuringGC) {
186 HandleMark hm; // handle scope
187 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);
188 Universe::heap()->prepare_for_verify();
189 // Note: we can verify only the heap here. When an object is
190 // marked, the previous value of the mark word (including
191 // identity hash values, ages, etc) is preserved, and the mark
192 // word is set to markOop::marked_value - effectively removing
193 // any hash values from the mark word. These hash values are
194 // used when verifying the dictionaries and so removing them
195 // from the mark word can make verification of the dictionaries
196 // fail. At the end of the GC, the orginal mark word values
197 // (including hash values) are restored to the appropriate
198 // objects.
199 if (!VerifySilently) {
200 gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying ");
201 }
202 Universe::heap()->verify(VerifySilently, VerifyOption_G1UseMarkWord);
203 if (!VerifySilently) {
204 gclog_or_tty->print_cr("]");
205 }
206 }
207
208 gc_tracer()->report_object_count_after_gc(&GenMarkSweep::is_alive);
209 }
210
211
212 void G1MarkSweep::mark_sweep_phase2() {
213 // Now all live objects are marked, compute the new object addresses.
214
215 // It is not required that we traverse spaces in the same order in
216 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
217 // tracking expects us to do so. See comment under phase4.
218
219 GCTraceTime tm("phase 2", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
220 GenMarkSweep::trace("2");
221
222 prepare_compaction();
223 }
224
225 class G1AdjustPointersClosure: public HeapRegionClosure {
226 public:
227 bool doHeapRegion(HeapRegion* r) {
228 if (r->isHumongous()) {
229 if (r->startsHumongous()) {
230 // We must adjust the pointers on the single H object.
231 oop obj = oop(r->bottom());
232 // point all the oops to the new location
233 obj->adjust_pointers();
234 }
235 } else {
236 // This really ought to be "as_CompactibleSpace"...
237 r->adjust_pointers();
238 }
239 return false;
240 }
241 };
242
243 class G1AlwaysTrueClosure: public BoolObjectClosure {
244 public:
245 bool do_object_b(oop p) { return true; }
246 };
247 static G1AlwaysTrueClosure always_true;
248
249 void G1MarkSweep::mark_sweep_phase3() {
250 G1CollectedHeap* g1h = G1CollectedHeap::heap();
251
252 // Adjust the pointers to reflect the new locations
253 GCTraceTime tm("phase 3", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
254 GenMarkSweep::trace("3");
255
256 // Need cleared claim bits for the roots processing
257 ClassLoaderDataGraph::clear_claimed_marks();
258
259 CodeBlobToOopClosure adjust_code_closure(&GenMarkSweep::adjust_pointer_closure, CodeBlobToOopClosure::FixRelocations);
260 {
261 G1RootProcessor root_processor(g1h);
262 root_processor.process_all_roots(&GenMarkSweep::adjust_pointer_closure,
263 &GenMarkSweep::adjust_cld_closure,
264 &adjust_code_closure);
265 }
266
267 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
268 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_pointer_closure);
269
270 // Now adjust pointers in remaining weak roots. (All of which should
271 // have been cleared if they pointed to non-surviving objects.)
272 JNIHandles::weak_oops_do(&always_true, &GenMarkSweep::adjust_pointer_closure);
273 JFR_ONLY(Jfr::weak_oops_do(&always_true, &GenMarkSweep::adjust_pointer_closure));
274
275 if (G1StringDedup::is_enabled()) {
276 G1StringDedup::oops_do(&GenMarkSweep::adjust_pointer_closure);
277 }
278
279 GenMarkSweep::adjust_marks();
280
281 G1AdjustPointersClosure blk;
282 g1h->heap_region_iterate(&blk);
283 }
284
285 class G1SpaceCompactClosure: public HeapRegionClosure {
286 public:
287 G1SpaceCompactClosure() {}
288
289 bool doHeapRegion(HeapRegion* hr) {
290 if (hr->isHumongous()) {
291 if (hr->startsHumongous()) {
292 oop obj = oop(hr->bottom());
293 if (obj->is_gc_marked()) {
294 obj->init_mark();
295 } else {
296 assert(hr->is_empty(), "Should have been cleared in phase 2.");
297 }
298 hr->reset_during_compaction();
299 }
300 } else {
301 hr->compact();
302 }
303 return false;
304 }
305 };
306
307 void G1MarkSweep::mark_sweep_phase4() {
308 // All pointers are now adjusted, move objects accordingly
309
310 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
311 // in the same order in phase2, phase3 and phase4. We don't quite do that
312 // here (code and comment not fixed for perm removal), so we tell the validate code
313 // to use a higher index (saved from phase2) when verifying perm_gen.
314 G1CollectedHeap* g1h = G1CollectedHeap::heap();
315
316 GCTraceTime tm("phase 4", G1Log::fine() && Verbose, true, gc_timer(), gc_tracer()->gc_id());
317 GenMarkSweep::trace("4");
318
319 G1SpaceCompactClosure blk;
320 g1h->heap_region_iterate(&blk);
321
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->startsHumongous(),
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->isHumongous()) {
373 if (hr->startsHumongous()) {
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->continuesHumongous(), "Invalid humongous.");
382 }
383 } else {
384 prepare_for_compaction(hr, hr->end());
385 }
386 return false;
387 }