Sat, 01 Sep 2012 13:25:18 -0400
6964458: Reimplement class meta-data storage to use native memory
Summary: Remove PermGen, allocate meta-data in metaspace linked to class loaders, rewrite GC walking, rewrite and rename metadata to be C++ classes
Reviewed-by: jmasa, stefank, never, coleenp, kvn, brutisso, mgerdin, dholmes, jrose, twisti, roland
Contributed-by: jmasa <jon.masamitsu@oracle.com>, stefank <stefan.karlsson@oracle.com>, mgerdin <mikael.gerdin@oracle.com>, never <tom.rodriguez@oracle.com>
1 /*
2 * Copyright (c) 2001, 2012, 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.
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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21 * questions.
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23 */
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 "memory/gcLocker.hpp"
35 #include "memory/genCollectedHeap.hpp"
36 #include "memory/modRefBarrierSet.hpp"
37 #include "memory/referencePolicy.hpp"
38 #include "memory/space.hpp"
39 #include "oops/instanceRefKlass.hpp"
40 #include "oops/oop.inline.hpp"
41 #include "prims/jvmtiExport.hpp"
42 #include "runtime/aprofiler.hpp"
43 #include "runtime/biasedLocking.hpp"
44 #include "runtime/fprofiler.hpp"
45 #include "runtime/synchronizer.hpp"
46 #include "runtime/thread.hpp"
47 #include "runtime/vmThread.hpp"
48 #include "utilities/copy.hpp"
49 #include "utilities/events.hpp"
51 class HeapRegion;
53 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
54 bool clear_all_softrefs) {
55 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
57 SharedHeap* sh = SharedHeap::heap();
58 #ifdef ASSERT
59 if (sh->collector_policy()->should_clear_all_soft_refs()) {
60 assert(clear_all_softrefs, "Policy should have been checked earler");
61 }
62 #endif
63 // hook up weak ref data so it can be used during Mark-Sweep
64 assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
65 assert(rp != NULL, "should be non-NULL");
66 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition");
68 GenMarkSweep::_ref_processor = rp;
69 rp->setup_policy(clear_all_softrefs);
71 // When collecting the permanent generation Method*s may be moving,
72 // so we either have to flush all bcp data or convert it into bci.
73 CodeCache::gc_prologue();
74 Threads::gc_prologue();
76 bool marked_for_unloading = false;
78 allocate_stacks();
80 // We should save the marks of the currently locked biased monitors.
81 // The marking doesn't preserve the marks of biased objects.
82 BiasedLocking::preserve_marks();
84 mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
86 mark_sweep_phase2();
88 // Don't add any more derived pointers during phase3
89 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
91 mark_sweep_phase3();
93 mark_sweep_phase4();
95 GenMarkSweep::restore_marks();
96 BiasedLocking::restore_marks();
97 GenMarkSweep::deallocate_stacks();
99 // "free at last gc" is calculated from these.
100 // CHF: cheating for now!!!
101 // Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity());
102 // Universe::set_heap_used_at_last_gc(Universe::heap()->used());
104 Threads::gc_epilogue();
105 CodeCache::gc_epilogue();
106 JvmtiExport::gc_epilogue();
108 // refs processing: clean slate
109 GenMarkSweep::_ref_processor = NULL;
110 }
113 void G1MarkSweep::allocate_stacks() {
114 GenMarkSweep::_preserved_count_max = 0;
115 GenMarkSweep::_preserved_marks = NULL;
116 GenMarkSweep::_preserved_count = 0;
117 }
119 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
120 bool clear_all_softrefs) {
121 // Recursively traverse all live objects and mark them
122 TraceTime tm("phase 1", G1Log::fine() && Verbose, true, gclog_or_tty);
123 GenMarkSweep::trace(" 1");
125 SharedHeap* sh = SharedHeap::heap();
127 // Need cleared claim bits for the strong roots processing
128 ClassLoaderDataGraph::clear_claimed_marks();
130 sh->process_strong_roots(true, // activate StrongRootsScope
131 false, // not scavenging.
132 SharedHeap::SO_SystemClasses,
133 &GenMarkSweep::follow_root_closure,
134 &GenMarkSweep::follow_code_root_closure,
135 &GenMarkSweep::follow_klass_closure);
137 // Process reference objects found during marking
138 ReferenceProcessor* rp = GenMarkSweep::ref_processor();
139 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Sanity");
141 rp->setup_policy(clear_all_softrefs);
142 rp->process_discovered_references(&GenMarkSweep::is_alive,
143 &GenMarkSweep::keep_alive,
144 &GenMarkSweep::follow_stack_closure,
145 NULL);
147 // Follow system dictionary roots and unload classes
148 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
149 assert(GenMarkSweep::_marking_stack.is_empty(),
150 "stack should be empty by now");
152 // Follow code cache roots (has to be done after system dictionary,
153 // assumes all live klasses are marked)
154 CodeCache::do_unloading(&GenMarkSweep::is_alive,
155 &GenMarkSweep::keep_alive,
156 purged_class);
157 GenMarkSweep::follow_stack();
159 // Update subklass/sibling/implementor links of live klasses
160 Klass::clean_weak_klass_links(&GenMarkSweep::is_alive);
161 assert(GenMarkSweep::_marking_stack.is_empty(),
162 "stack should be empty by now");
164 // Visit interned string tables and delete unmarked oops
165 StringTable::unlink(&GenMarkSweep::is_alive);
166 // Clean up unreferenced symbols in symbol table.
167 SymbolTable::unlink();
169 assert(GenMarkSweep::_marking_stack.is_empty(),
170 "stack should be empty by now");
172 if (VerifyDuringGC) {
173 HandleMark hm; // handle scope
174 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);
175 gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying ");
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 orginal mark word values
185 // (including hash values) are restored to the appropriate
186 // objects.
187 Universe::heap()->verify(/* silent */ false,
188 /* option */ VerifyOption_G1UseMarkWord);
190 G1CollectedHeap* g1h = G1CollectedHeap::heap();
191 gclog_or_tty->print_cr("]");
192 }
193 }
195 class G1PrepareCompactClosure: public HeapRegionClosure {
196 G1CollectedHeap* _g1h;
197 ModRefBarrierSet* _mrbs;
198 CompactPoint _cp;
199 HumongousRegionSet _humongous_proxy_set;
201 void free_humongous_region(HeapRegion* hr) {
202 HeapWord* end = hr->end();
203 size_t dummy_pre_used;
204 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
206 assert(hr->startsHumongous(),
207 "Only the start of a humongous region should be freed.");
208 _g1h->free_humongous_region(hr, &dummy_pre_used, &dummy_free_list,
209 &_humongous_proxy_set, false /* par */);
210 hr->prepare_for_compaction(&_cp);
211 // Also clear the part of the card table that will be unused after
212 // compaction.
213 _mrbs->clear(MemRegion(hr->compaction_top(), end));
214 dummy_free_list.remove_all();
215 }
217 public:
218 G1PrepareCompactClosure(CompactibleSpace* cs)
219 : _g1h(G1CollectedHeap::heap()),
220 _mrbs(G1CollectedHeap::heap()->mr_bs()),
221 _cp(NULL, cs, cs->initialize_threshold()),
222 _humongous_proxy_set("G1MarkSweep Humongous Proxy Set") { }
224 void update_sets() {
225 // We'll recalculate total used bytes and recreate the free list
226 // at the end of the GC, so no point in updating those values here.
227 _g1h->update_sets_after_freeing_regions(0, /* pre_used */
228 NULL, /* free_list */
229 NULL, /* old_proxy_set */
230 &_humongous_proxy_set,
231 false /* par */);
232 }
234 bool doHeapRegion(HeapRegion* hr) {
235 if (hr->isHumongous()) {
236 if (hr->startsHumongous()) {
237 oop obj = oop(hr->bottom());
238 if (obj->is_gc_marked()) {
239 obj->forward_to(obj);
240 } else {
241 free_humongous_region(hr);
242 }
243 } else {
244 assert(hr->continuesHumongous(), "Invalid humongous.");
245 }
246 } else {
247 hr->prepare_for_compaction(&_cp);
248 // Also clear the part of the card table that will be unused after
249 // compaction.
250 _mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
251 }
252 return false;
253 }
254 };
256 void G1MarkSweep::mark_sweep_phase2() {
257 // Now all live objects are marked, compute the new object addresses.
259 // It is not required that we traverse spaces in the same order in
260 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
261 // tracking expects us to do so. See comment under phase4.
263 G1CollectedHeap* g1h = G1CollectedHeap::heap();
265 TraceTime tm("phase 2", G1Log::fine() && Verbose, true, gclog_or_tty);
266 GenMarkSweep::trace("2");
268 // find the first region
269 HeapRegion* r = g1h->region_at(0);
270 CompactibleSpace* sp = r;
271 if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) {
272 sp = r->next_compaction_space();
273 }
275 G1PrepareCompactClosure blk(sp);
276 g1h->heap_region_iterate(&blk);
277 blk.update_sets();
278 }
280 class G1AdjustPointersClosure: public HeapRegionClosure {
281 public:
282 bool doHeapRegion(HeapRegion* r) {
283 if (r->isHumongous()) {
284 if (r->startsHumongous()) {
285 // We must adjust the pointers on the single H object.
286 oop obj = oop(r->bottom());
287 debug_only(GenMarkSweep::track_interior_pointers(obj));
288 // point all the oops to the new location
289 obj->adjust_pointers();
290 debug_only(GenMarkSweep::check_interior_pointers());
291 }
292 } else {
293 // This really ought to be "as_CompactibleSpace"...
294 r->adjust_pointers();
295 }
296 return false;
297 }
298 };
300 void G1MarkSweep::mark_sweep_phase3() {
301 G1CollectedHeap* g1h = G1CollectedHeap::heap();
303 // Adjust the pointers to reflect the new locations
304 TraceTime tm("phase 3", G1Log::fine() && Verbose, true, gclog_or_tty);
305 GenMarkSweep::trace("3");
307 SharedHeap* sh = SharedHeap::heap();
309 // Need cleared claim bits for the strong roots processing
310 ClassLoaderDataGraph::clear_claimed_marks();
312 sh->process_strong_roots(true, // activate StrongRootsScope
313 false, // not scavenging.
314 SharedHeap::SO_AllClasses,
315 &GenMarkSweep::adjust_root_pointer_closure,
316 NULL, // do not touch code cache here
317 &GenMarkSweep::adjust_klass_closure);
319 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
320 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_root_pointer_closure);
322 // Now adjust pointers in remaining weak roots. (All of which should
323 // have been cleared if they pointed to non-surviving objects.)
324 g1h->g1_process_weak_roots(&GenMarkSweep::adjust_root_pointer_closure,
325 &GenMarkSweep::adjust_pointer_closure);
327 GenMarkSweep::adjust_marks();
329 G1AdjustPointersClosure blk;
330 g1h->heap_region_iterate(&blk);
331 }
333 class G1SpaceCompactClosure: public HeapRegionClosure {
334 public:
335 G1SpaceCompactClosure() {}
337 bool doHeapRegion(HeapRegion* hr) {
338 if (hr->isHumongous()) {
339 if (hr->startsHumongous()) {
340 oop obj = oop(hr->bottom());
341 if (obj->is_gc_marked()) {
342 obj->init_mark();
343 } else {
344 assert(hr->is_empty(), "Should have been cleared in phase 2.");
345 }
346 hr->reset_during_compaction();
347 }
348 } else {
349 hr->compact();
350 }
351 return false;
352 }
353 };
355 void G1MarkSweep::mark_sweep_phase4() {
356 // All pointers are now adjusted, move objects accordingly
358 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
359 // in the same order in phase2, phase3 and phase4. We don't quite do that
360 // here (code and comment not fixed for perm removal), so we tell the validate code
361 // to use a higher index (saved from phase2) when verifying perm_gen.
362 G1CollectedHeap* g1h = G1CollectedHeap::heap();
364 TraceTime tm("phase 4", G1Log::fine() && Verbose, true, gclog_or_tty);
365 GenMarkSweep::trace("4");
367 G1SpaceCompactClosure blk;
368 g1h->heap_region_iterate(&blk);
370 }