1 /*
2 * Copyright (c) 2001, 2019, 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/classLoaderDataGraph.hpp"
27 #include "classfile/javaClasses.hpp"
28 #include "classfile/stringTable.hpp"
29 #include "classfile/symbolTable.hpp"
30 #include "classfile/systemDictionary.hpp"
31 #include "classfile/vmSymbols.hpp"
32 #include "code/codeCache.hpp"
33 #include "code/icBuffer.hpp"
34 #include "gc/serial/genMarkSweep.hpp"
35 #include "gc/shared/collectedHeap.inline.hpp"
36 #include "gc/shared/gcHeapSummary.hpp"
37 #include "gc/shared/gcTimer.hpp"
38 #include "gc/shared/gcTrace.hpp"
39 #include "gc/shared/gcTraceTime.inline.hpp"
40 #include "gc/shared/genCollectedHeap.hpp"
41 #include "gc/shared/generation.hpp"
42 #include "gc/shared/genOopClosures.inline.hpp"
43 #include "gc/shared/modRefBarrierSet.hpp"
44 #include "gc/shared/referencePolicy.hpp"
45 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
46 #include "gc/shared/space.hpp"
47 #include "gc/shared/strongRootsScope.hpp"
48 #include "gc/shared/weakProcessor.hpp"
49 #include "memory/universe.hpp"
50 #include "oops/instanceRefKlass.hpp"
51 #include "oops/oop.inline.hpp"
52 #include "prims/jvmtiExport.hpp"
53 #include "runtime/handles.inline.hpp"
54 #include "runtime/synchronizer.hpp"
55 #include "runtime/thread.inline.hpp"
56 #include "runtime/vmThread.hpp"
57 #include "utilities/copy.hpp"
58 #include "utilities/events.hpp"
59 #include "utilities/stack.inline.hpp"
60 #if INCLUDE_JVMCI
61 #include "jvmci/jvmci.hpp"
62 #endif
63
64 void GenMarkSweep::invoke_at_safepoint(ReferenceProcessor* rp, bool clear_all_softrefs) {
65 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
66
67 GenCollectedHeap* gch = GenCollectedHeap::heap();
68 #ifdef ASSERT
69 if (gch->soft_ref_policy()->should_clear_all_soft_refs()) {
70 assert(clear_all_softrefs, "Policy should have been checked earlier");
71 }
72 #endif
73
74 // hook up weak ref data so it can be used during Mark-Sweep
75 assert(ref_processor() == NULL, "no stomping");
76 assert(rp != NULL, "should be non-NULL");
77 set_ref_processor(rp);
78 rp->setup_policy(clear_all_softrefs);
79
80 gch->trace_heap_before_gc(_gc_tracer);
81
82 // Increment the invocation count
83 _total_invocations++;
84
85 // Capture used regions for each generation that will be
86 // subject to collection, so that card table adjustments can
87 // be made intelligently (see clear / invalidate further below).
88 gch->save_used_regions();
89
90 allocate_stacks();
91
92 mark_sweep_phase1(clear_all_softrefs);
93
94 mark_sweep_phase2();
95
96 // Don't add any more derived pointers during phase3
97 #if COMPILER2_OR_JVMCI
98 assert(DerivedPointerTable::is_active(), "Sanity");
99 DerivedPointerTable::set_active(false);
100 #endif
101
102 mark_sweep_phase3();
103
104 mark_sweep_phase4();
105
106 restore_marks();
107
108 // Set saved marks for allocation profiler (and other things? -- dld)
109 // (Should this be in general part?)
110 gch->save_marks();
111
112 deallocate_stacks();
113
114 // If compaction completely evacuated the young generation then we
115 // can clear the card table. Otherwise, we must invalidate
116 // it (consider all cards dirty). In the future, we might consider doing
117 // compaction within generations only, and doing card-table sliding.
118 CardTableRS* rs = gch->rem_set();
119 Generation* old_gen = gch->old_gen();
120
121 // Clear/invalidate below make use of the "prev_used_regions" saved earlier.
122 if (gch->young_gen()->used() == 0) {
123 // We've evacuated the young generation.
124 rs->clear_into_younger(old_gen);
125 } else {
126 // Invalidate the cards corresponding to the currently used
127 // region and clear those corresponding to the evacuated region.
128 rs->invalidate_or_clear(old_gen);
129 }
130
131 gch->prune_scavengable_nmethods();
132
133 // refs processing: clean slate
134 set_ref_processor(NULL);
135
136 // Update heap occupancy information which is used as
137 // input to soft ref clearing policy at the next gc.
138 Universe::update_heap_info_at_gc();
139
140 Universe::heap()->next_whole_heap_examined();
141
142 gch->trace_heap_after_gc(_gc_tracer);
143 }
144
145 void GenMarkSweep::allocate_stacks() {
146 GenCollectedHeap* gch = GenCollectedHeap::heap();
147 // Scratch request on behalf of old generation; will do no allocation.
148 ScratchBlock* scratch = gch->gather_scratch(gch->old_gen(), 0);
149
150 // $$$ To cut a corner, we'll only use the first scratch block, and then
151 // revert to malloc.
152 if (scratch != NULL) {
153 _preserved_count_max =
154 scratch->num_words * HeapWordSize / sizeof(PreservedMark);
155 } else {
156 _preserved_count_max = 0;
157 }
158
159 _preserved_marks = (PreservedMark*)scratch;
160 _preserved_count = 0;
161 }
162
163
164 void GenMarkSweep::deallocate_stacks() {
165 GenCollectedHeap* gch = GenCollectedHeap::heap();
166 gch->release_scratch();
167
168 _preserved_mark_stack.clear(true);
169 _preserved_oop_stack.clear(true);
170 _marking_stack.clear();
171 _objarray_stack.clear(true);
172 }
173
174 void GenMarkSweep::mark_sweep_phase1(bool clear_all_softrefs) {
175 // Recursively traverse all live objects and mark them
176 GCTraceTime(Info, gc, phases) tm("Phase 1: Mark live objects", _gc_timer);
177
178 GenCollectedHeap* gch = GenCollectedHeap::heap();
179
180 // Because follow_root_closure is created statically, cannot
181 // use OopsInGenClosure constructor which takes a generation,
182 // as the Universe has not been created when the static constructors
183 // are run.
184 follow_root_closure.set_orig_generation(gch->old_gen());
185
186 // Need new claim bits before marking starts.
187 ClassLoaderDataGraph::clear_claimed_marks();
188
189 {
190 StrongRootsScope srs(1);
191
192 gch->full_process_roots(&srs,
193 false, // not the adjust phase
194 GenCollectedHeap::SO_None,
195 ClassUnloading, // only strong roots if ClassUnloading
196 // is enabled
197 &follow_root_closure,
198 &follow_cld_closure);
199 }
200
201 // Process reference objects found during marking
202 {
203 GCTraceTime(Debug, gc, phases) tm_m("Reference Processing", gc_timer());
204
205 ref_processor()->setup_policy(clear_all_softrefs);
206 ReferenceProcessorPhaseTimes pt(_gc_timer, ref_processor()->max_num_queues());
207 const ReferenceProcessorStats& stats =
208 ref_processor()->process_discovered_references(
209 &is_alive, &keep_alive, &follow_stack_closure, NULL, &pt);
210 pt.print_all_references();
211 gc_tracer()->report_gc_reference_stats(stats);
212 }
213
214 // This is the point where the entire marking should have completed.
215 assert(_marking_stack.is_empty(), "Marking should have completed");
216
217 {
218 GCTraceTime(Debug, gc, phases) tm_m("Weak Processing", gc_timer());
219 WeakProcessor::weak_oops_do(&is_alive, &do_nothing_cl);
220 }
221
222 {
223 GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", gc_timer());
224
225 // Unload classes and purge the SystemDictionary.
226 bool purged_class = SystemDictionary::do_unloading(gc_timer());
227
228 // Unload nmethods.
229 CodeCache::do_unloading(&is_alive, purged_class);
230
231 // Prune dead klasses from subklass/sibling/implementor lists.
232 Klass::clean_weak_klass_links(purged_class);
233
234 // Clean JVMCI metadata handles.
235 JVMCI_ONLY(JVMCI::do_unloading(purged_class));
236 }
237
238 gc_tracer()->report_object_count_after_gc(&is_alive);
239 }
240
241
242 void GenMarkSweep::mark_sweep_phase2() {
243 // Now all live objects are marked, compute the new object addresses.
244
245 // It is imperative that we traverse perm_gen LAST. If dead space is
246 // allowed a range of dead object may get overwritten by a dead int
247 // array. If perm_gen is not traversed last a Klass* may get
248 // overwritten. This is fine since it is dead, but if the class has dead
249 // instances we have to skip them, and in order to find their size we
250 // need the Klass*!
251 //
252 // It is not required that we traverse spaces in the same order in
253 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
254 // tracking expects us to do so. See comment under phase4.
255
256 GenCollectedHeap* gch = GenCollectedHeap::heap();
257
258 GCTraceTime(Info, gc, phases) tm("Phase 2: Compute new object addresses", _gc_timer);
259
260 gch->prepare_for_compaction();
261 }
262
263 class GenAdjustPointersClosure: public GenCollectedHeap::GenClosure {
264 public:
265 void do_generation(Generation* gen) {
266 gen->adjust_pointers();
267 }
268 };
269
270 void GenMarkSweep::mark_sweep_phase3() {
271 GenCollectedHeap* gch = GenCollectedHeap::heap();
272
273 // Adjust the pointers to reflect the new locations
274 GCTraceTime(Info, gc, phases) tm("Phase 3: Adjust pointers", gc_timer());
275
276 // Need new claim bits for the pointer adjustment tracing.
277 ClassLoaderDataGraph::clear_claimed_marks();
278
279 // Because the closure below is created statically, we cannot
280 // use OopsInGenClosure constructor which takes a generation,
281 // as the Universe has not been created when the static constructors
282 // are run.
283 adjust_pointer_closure.set_orig_generation(gch->old_gen());
284
285 {
286 StrongRootsScope srs(1);
287
288 gch->full_process_roots(&srs,
289 true, // this is the adjust phase
290 GenCollectedHeap::SO_AllCodeCache,
291 false, // all roots
292 &adjust_pointer_closure,
293 &adjust_cld_closure);
294 }
295
296 gch->gen_process_weak_roots(&adjust_pointer_closure);
297
298 adjust_marks();
299 GenAdjustPointersClosure blk;
300 gch->generation_iterate(&blk, true);
301 }
302
303 class GenCompactClosure: public GenCollectedHeap::GenClosure {
304 public:
305 void do_generation(Generation* gen) {
306 gen->compact();
307 }
308 };
309
310 void GenMarkSweep::mark_sweep_phase4() {
311 // All pointers are now adjusted, move objects accordingly
312
313 // It is imperative that we traverse perm_gen first in phase4. All
314 // classes must be allocated earlier than their instances, and traversing
315 // perm_gen first makes sure that all Klass*s have moved to their new
316 // location before any instance does a dispatch through it's klass!
317
318 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
319 // in the same order in phase2, phase3 and phase4. We don't quite do that
320 // here (perm_gen first rather than last), so we tell the validate code
321 // to use a higher index (saved from phase2) when verifying perm_gen.
322 GenCollectedHeap* gch = GenCollectedHeap::heap();
323
324 GCTraceTime(Info, gc, phases) tm("Phase 4: Move objects", _gc_timer);
325
326 GenCompactClosure blk;
327 gch->generation_iterate(&blk, true);
328 }