Thu, 27 Jan 2011 16:11:27 -0800
6990754: Use native memory and reference counting to implement SymbolTable
Summary: move symbols from permgen into C heap and reference count them
Reviewed-by: never, acorn, jmasa, stefank
1 /*
2 * Copyright (c) 2001, 2011, 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.
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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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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/g1MarkSweep.hpp"
33 #include "memory/gcLocker.hpp"
34 #include "memory/genCollectedHeap.hpp"
35 #include "memory/modRefBarrierSet.hpp"
36 #include "memory/referencePolicy.hpp"
37 #include "memory/space.hpp"
38 #include "oops/instanceRefKlass.hpp"
39 #include "oops/oop.inline.hpp"
40 #include "prims/jvmtiExport.hpp"
41 #include "runtime/aprofiler.hpp"
42 #include "runtime/biasedLocking.hpp"
43 #include "runtime/fprofiler.hpp"
44 #include "runtime/synchronizer.hpp"
45 #include "runtime/thread.hpp"
46 #include "runtime/vmThread.hpp"
47 #include "utilities/copy.hpp"
48 #include "utilities/events.hpp"
50 class HeapRegion;
52 void G1MarkSweep::invoke_at_safepoint(ReferenceProcessor* rp,
53 bool clear_all_softrefs) {
54 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
56 SharedHeap* sh = SharedHeap::heap();
57 #ifdef ASSERT
58 if (sh->collector_policy()->should_clear_all_soft_refs()) {
59 assert(clear_all_softrefs, "Policy should have been checked earler");
60 }
61 #endif
62 // hook up weak ref data so it can be used during Mark-Sweep
63 assert(GenMarkSweep::ref_processor() == NULL, "no stomping");
64 assert(rp != NULL, "should be non-NULL");
65 GenMarkSweep::_ref_processor = rp;
66 rp->setup_policy(clear_all_softrefs);
68 // When collecting the permanent generation methodOops may be moving,
69 // so we either have to flush all bcp data or convert it into bci.
70 CodeCache::gc_prologue();
71 Threads::gc_prologue();
73 // Increment the invocation count for the permanent generation, since it is
74 // implicitly collected whenever we do a full mark sweep collection.
75 sh->perm_gen()->stat_record()->invocations++;
77 bool marked_for_unloading = false;
79 allocate_stacks();
81 // We should save the marks of the currently locked biased monitors.
82 // The marking doesn't preserve the marks of biased objects.
83 BiasedLocking::preserve_marks();
85 mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
87 if (VerifyDuringGC) {
88 G1CollectedHeap* g1h = G1CollectedHeap::heap();
89 g1h->checkConcurrentMark();
90 }
92 mark_sweep_phase2();
94 // Don't add any more derived pointers during phase3
95 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
97 mark_sweep_phase3();
99 mark_sweep_phase4();
101 GenMarkSweep::restore_marks();
102 BiasedLocking::restore_marks();
103 GenMarkSweep::deallocate_stacks();
105 // We must invalidate the perm-gen rs, so that it gets rebuilt.
106 GenRemSet* rs = sh->rem_set();
107 rs->invalidate(sh->perm_gen()->used_region(), true /*whole_heap*/);
109 // "free at last gc" is calculated from these.
110 // CHF: cheating for now!!!
111 // Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity());
112 // Universe::set_heap_used_at_last_gc(Universe::heap()->used());
114 Threads::gc_epilogue();
115 CodeCache::gc_epilogue();
116 JvmtiExport::gc_epilogue();
118 // refs processing: clean slate
119 GenMarkSweep::_ref_processor = NULL;
120 }
123 void G1MarkSweep::allocate_stacks() {
124 GenMarkSweep::_preserved_count_max = 0;
125 GenMarkSweep::_preserved_marks = NULL;
126 GenMarkSweep::_preserved_count = 0;
127 }
129 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
130 bool clear_all_softrefs) {
131 // Recursively traverse all live objects and mark them
132 EventMark m("1 mark object");
133 TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
134 GenMarkSweep::trace(" 1");
136 SharedHeap* sh = SharedHeap::heap();
138 sh->process_strong_roots(true, // activeate StrongRootsScope
139 true, // Collecting permanent generation.
140 SharedHeap::SO_SystemClasses,
141 &GenMarkSweep::follow_root_closure,
142 &GenMarkSweep::follow_code_root_closure,
143 &GenMarkSweep::follow_root_closure);
145 // Process reference objects found during marking
146 ReferenceProcessor* rp = GenMarkSweep::ref_processor();
147 rp->setup_policy(clear_all_softrefs);
148 rp->process_discovered_references(&GenMarkSweep::is_alive,
149 &GenMarkSweep::keep_alive,
150 &GenMarkSweep::follow_stack_closure,
151 NULL);
153 // Follow system dictionary roots and unload classes
154 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
155 assert(GenMarkSweep::_marking_stack.is_empty(),
156 "stack should be empty by now");
158 // Follow code cache roots (has to be done after system dictionary,
159 // assumes all live klasses are marked)
160 CodeCache::do_unloading(&GenMarkSweep::is_alive,
161 &GenMarkSweep::keep_alive,
162 purged_class);
163 GenMarkSweep::follow_stack();
165 // Update subklass/sibling/implementor links of live klasses
166 GenMarkSweep::follow_weak_klass_links();
167 assert(GenMarkSweep::_marking_stack.is_empty(),
168 "stack should be empty by now");
170 // Visit memoized MDO's and clear any unmarked weak refs
171 GenMarkSweep::follow_mdo_weak_refs();
172 assert(GenMarkSweep::_marking_stack.is_empty(), "just drained");
175 // Visit interned string tables and delete unmarked oops
176 StringTable::unlink(&GenMarkSweep::is_alive);
177 // Clean up unreferenced symbols in symbol table.
178 SymbolTable::unlink();
180 assert(GenMarkSweep::_marking_stack.is_empty(),
181 "stack should be empty by now");
182 }
184 class G1PrepareCompactClosure: public HeapRegionClosure {
185 G1CollectedHeap* _g1h;
186 ModRefBarrierSet* _mrbs;
187 CompactPoint _cp;
188 size_t _pre_used;
189 FreeRegionList _free_list;
190 HumongousRegionSet _humongous_proxy_set;
192 void free_humongous_region(HeapRegion* hr) {
193 HeapWord* end = hr->end();
194 assert(hr->startsHumongous(),
195 "Only the start of a humongous region should be freed.");
196 _g1h->free_humongous_region(hr, &_pre_used, &_free_list,
197 &_humongous_proxy_set, false /* par */);
198 // Do we also need to do this for the continues humongous regions
199 // we just collapsed?
200 hr->prepare_for_compaction(&_cp);
201 // Also clear the part of the card table that will be unused after
202 // compaction.
203 _mrbs->clear(MemRegion(hr->compaction_top(), end));
204 }
206 public:
207 G1PrepareCompactClosure(CompactibleSpace* cs)
208 : _g1h(G1CollectedHeap::heap()),
209 _mrbs(G1CollectedHeap::heap()->mr_bs()),
210 _cp(NULL, cs, cs->initialize_threshold()),
211 _pre_used(0),
212 _free_list("Local Free List for G1MarkSweep"),
213 _humongous_proxy_set("G1MarkSweep Humongous Proxy Set") { }
215 void update_sets() {
216 // We'll recalculate total used bytes and recreate the free list
217 // at the end of the GC, so no point in updating those values here.
218 _g1h->update_sets_after_freeing_regions(0, /* pre_used */
219 NULL, /* free_list */
220 &_humongous_proxy_set,
221 false /* par */);
222 _free_list.remove_all();
223 }
225 bool doHeapRegion(HeapRegion* hr) {
226 if (hr->isHumongous()) {
227 if (hr->startsHumongous()) {
228 oop obj = oop(hr->bottom());
229 if (obj->is_gc_marked()) {
230 obj->forward_to(obj);
231 } else {
232 free_humongous_region(hr);
233 }
234 } else {
235 assert(hr->continuesHumongous(), "Invalid humongous.");
236 }
237 } else {
238 hr->prepare_for_compaction(&_cp);
239 // Also clear the part of the card table that will be unused after
240 // compaction.
241 _mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
242 }
243 return false;
244 }
245 };
247 // Finds the first HeapRegion.
248 class FindFirstRegionClosure: public HeapRegionClosure {
249 HeapRegion* _a_region;
250 public:
251 FindFirstRegionClosure() : _a_region(NULL) {}
252 bool doHeapRegion(HeapRegion* r) {
253 _a_region = r;
254 return true;
255 }
256 HeapRegion* result() { return _a_region; }
257 };
259 void G1MarkSweep::mark_sweep_phase2() {
260 // Now all live objects are marked, compute the new object addresses.
262 // It is imperative that we traverse perm_gen LAST. If dead space is
263 // allowed a range of dead object may get overwritten by a dead int
264 // array. If perm_gen is not traversed last a klassOop may get
265 // overwritten. This is fine since it is dead, but if the class has dead
266 // instances we have to skip them, and in order to find their size we
267 // need the klassOop!
268 //
269 // It is not required that we traverse spaces in the same order in
270 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
271 // tracking expects us to do so. See comment under phase4.
273 G1CollectedHeap* g1h = G1CollectedHeap::heap();
274 Generation* pg = g1h->perm_gen();
276 EventMark m("2 compute new addresses");
277 TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);
278 GenMarkSweep::trace("2");
280 FindFirstRegionClosure cl;
281 g1h->heap_region_iterate(&cl);
282 HeapRegion *r = cl.result();
283 CompactibleSpace* sp = r;
284 if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) {
285 sp = r->next_compaction_space();
286 }
288 G1PrepareCompactClosure blk(sp);
289 g1h->heap_region_iterate(&blk);
290 blk.update_sets();
292 CompactPoint perm_cp(pg, NULL, NULL);
293 pg->prepare_for_compaction(&perm_cp);
294 }
296 class G1AdjustPointersClosure: public HeapRegionClosure {
297 public:
298 bool doHeapRegion(HeapRegion* r) {
299 if (r->isHumongous()) {
300 if (r->startsHumongous()) {
301 // We must adjust the pointers on the single H object.
302 oop obj = oop(r->bottom());
303 debug_only(GenMarkSweep::track_interior_pointers(obj));
304 // point all the oops to the new location
305 obj->adjust_pointers();
306 debug_only(GenMarkSweep::check_interior_pointers());
307 }
308 } else {
309 // This really ought to be "as_CompactibleSpace"...
310 r->adjust_pointers();
311 }
312 return false;
313 }
314 };
316 void G1MarkSweep::mark_sweep_phase3() {
317 G1CollectedHeap* g1h = G1CollectedHeap::heap();
318 Generation* pg = g1h->perm_gen();
320 // Adjust the pointers to reflect the new locations
321 EventMark m("3 adjust pointers");
322 TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);
323 GenMarkSweep::trace("3");
325 SharedHeap* sh = SharedHeap::heap();
327 sh->process_strong_roots(true, // activate StrongRootsScope
328 true, // Collecting permanent generation.
329 SharedHeap::SO_AllClasses,
330 &GenMarkSweep::adjust_root_pointer_closure,
331 NULL, // do not touch code cache here
332 &GenMarkSweep::adjust_pointer_closure);
334 g1h->ref_processor()->weak_oops_do(&GenMarkSweep::adjust_root_pointer_closure);
336 // Now adjust pointers in remaining weak roots. (All of which should
337 // have been cleared if they pointed to non-surviving objects.)
338 g1h->g1_process_weak_roots(&GenMarkSweep::adjust_root_pointer_closure,
339 &GenMarkSweep::adjust_pointer_closure);
341 GenMarkSweep::adjust_marks();
343 G1AdjustPointersClosure blk;
344 g1h->heap_region_iterate(&blk);
345 pg->adjust_pointers();
346 }
348 class G1SpaceCompactClosure: public HeapRegionClosure {
349 public:
350 G1SpaceCompactClosure() {}
352 bool doHeapRegion(HeapRegion* hr) {
353 if (hr->isHumongous()) {
354 if (hr->startsHumongous()) {
355 oop obj = oop(hr->bottom());
356 if (obj->is_gc_marked()) {
357 obj->init_mark();
358 } else {
359 assert(hr->is_empty(), "Should have been cleared in phase 2.");
360 }
361 hr->reset_during_compaction();
362 }
363 } else {
364 hr->compact();
365 }
366 return false;
367 }
368 };
370 void G1MarkSweep::mark_sweep_phase4() {
371 // All pointers are now adjusted, move objects accordingly
373 // It is imperative that we traverse perm_gen first in phase4. All
374 // classes must be allocated earlier than their instances, and traversing
375 // perm_gen first makes sure that all klassOops have moved to their new
376 // location before any instance does a dispatch through it's klass!
378 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
379 // in the same order in phase2, phase3 and phase4. We don't quite do that
380 // here (perm_gen first rather than last), so we tell the validate code
381 // to use a higher index (saved from phase2) when verifying perm_gen.
382 G1CollectedHeap* g1h = G1CollectedHeap::heap();
383 Generation* pg = g1h->perm_gen();
385 EventMark m("4 compact heap");
386 TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty);
387 GenMarkSweep::trace("4");
389 pg->compact();
391 G1SpaceCompactClosure blk;
392 g1h->heap_region_iterate(&blk);
394 }
396 // Local Variables: ***
397 // c-indentation-style: gnu ***
398 // End: ***