Tue, 20 Sep 2011 09:59:59 -0400
7059019: G1: add G1 support to the SA
Summary: Extend the SA to recognize the G1CollectedHeap and implement any code that's needed by our serviceability tools (jmap, jinfo, jstack, etc.) that depend on the SA.
Reviewed-by: never, poonam, johnc
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.
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5 * This code is free software; you can redistribute it and/or modify it
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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
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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 mark_sweep_phase2();
89 // Don't add any more derived pointers during phase3
90 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
92 mark_sweep_phase3();
94 mark_sweep_phase4();
96 GenMarkSweep::restore_marks();
97 BiasedLocking::restore_marks();
98 GenMarkSweep::deallocate_stacks();
100 // We must invalidate the perm-gen rs, so that it gets rebuilt.
101 GenRemSet* rs = sh->rem_set();
102 rs->invalidate(sh->perm_gen()->used_region(), true /*whole_heap*/);
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());
109 Threads::gc_epilogue();
110 CodeCache::gc_epilogue();
111 JvmtiExport::gc_epilogue();
113 // refs processing: clean slate
114 GenMarkSweep::_ref_processor = NULL;
115 }
118 void G1MarkSweep::allocate_stacks() {
119 GenMarkSweep::_preserved_count_max = 0;
120 GenMarkSweep::_preserved_marks = NULL;
121 GenMarkSweep::_preserved_count = 0;
122 }
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 EventMark m("1 mark object");
128 TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
129 GenMarkSweep::trace(" 1");
131 SharedHeap* sh = SharedHeap::heap();
133 sh->process_strong_roots(true, // activeate StrongRootsScope
134 true, // Collecting permanent generation.
135 SharedHeap::SO_SystemClasses,
136 &GenMarkSweep::follow_root_closure,
137 &GenMarkSweep::follow_code_root_closure,
138 &GenMarkSweep::follow_root_closure);
140 // Process reference objects found during marking
141 ReferenceProcessor* rp = GenMarkSweep::ref_processor();
142 rp->setup_policy(clear_all_softrefs);
143 rp->process_discovered_references(&GenMarkSweep::is_alive,
144 &GenMarkSweep::keep_alive,
145 &GenMarkSweep::follow_stack_closure,
146 NULL);
148 // Follow system dictionary roots and unload classes
149 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
150 assert(GenMarkSweep::_marking_stack.is_empty(),
151 "stack should be empty by now");
153 // Follow code cache roots (has to be done after system dictionary,
154 // assumes all live klasses are marked)
155 CodeCache::do_unloading(&GenMarkSweep::is_alive,
156 &GenMarkSweep::keep_alive,
157 purged_class);
158 GenMarkSweep::follow_stack();
160 // Update subklass/sibling/implementor links of live klasses
161 GenMarkSweep::follow_weak_klass_links();
162 assert(GenMarkSweep::_marking_stack.is_empty(),
163 "stack should be empty by now");
165 // Visit memoized MDO's and clear any unmarked weak refs
166 GenMarkSweep::follow_mdo_weak_refs();
167 assert(GenMarkSweep::_marking_stack.is_empty(), "just drained");
170 // Visit interned string tables and delete unmarked oops
171 StringTable::unlink(&GenMarkSweep::is_alive);
172 // Clean up unreferenced symbols in symbol table.
173 SymbolTable::unlink();
175 assert(GenMarkSweep::_marking_stack.is_empty(),
176 "stack should be empty by now");
178 if (VerifyDuringGC) {
179 HandleMark hm; // handle scope
180 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);
181 gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying ");
182 Universe::heap()->prepare_for_verify();
183 // Note: we can verify only the heap here. When an object is
184 // marked, the previous value of the mark word (including
185 // identity hash values, ages, etc) is preserved, and the mark
186 // word is set to markOop::marked_value - effectively removing
187 // any hash values from the mark word. These hash values are
188 // used when verifying the dictionaries and so removing them
189 // from the mark word can make verification of the dictionaries
190 // fail. At the end of the GC, the orginal mark word values
191 // (including hash values) are restored to the appropriate
192 // objects.
193 Universe::heap()->verify(/* allow dirty */ true,
194 /* silent */ false,
195 /* option */ VerifyOption_G1UseMarkWord);
197 G1CollectedHeap* g1h = G1CollectedHeap::heap();
198 gclog_or_tty->print_cr("]");
199 }
200 }
202 class G1PrepareCompactClosure: public HeapRegionClosure {
203 G1CollectedHeap* _g1h;
204 ModRefBarrierSet* _mrbs;
205 CompactPoint _cp;
206 HumongousRegionSet _humongous_proxy_set;
208 void free_humongous_region(HeapRegion* hr) {
209 HeapWord* end = hr->end();
210 size_t dummy_pre_used;
211 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
213 assert(hr->startsHumongous(),
214 "Only the start of a humongous region should be freed.");
215 _g1h->free_humongous_region(hr, &dummy_pre_used, &dummy_free_list,
216 &_humongous_proxy_set, false /* par */);
217 hr->prepare_for_compaction(&_cp);
218 // Also clear the part of the card table that will be unused after
219 // compaction.
220 _mrbs->clear(MemRegion(hr->compaction_top(), end));
221 dummy_free_list.remove_all();
222 }
224 public:
225 G1PrepareCompactClosure(CompactibleSpace* cs)
226 : _g1h(G1CollectedHeap::heap()),
227 _mrbs(G1CollectedHeap::heap()->mr_bs()),
228 _cp(NULL, cs, cs->initialize_threshold()),
229 _humongous_proxy_set("G1MarkSweep Humongous Proxy Set") { }
231 void update_sets() {
232 // We'll recalculate total used bytes and recreate the free list
233 // at the end of the GC, so no point in updating those values here.
234 _g1h->update_sets_after_freeing_regions(0, /* pre_used */
235 NULL, /* free_list */
236 &_humongous_proxy_set,
237 false /* par */);
238 }
240 bool doHeapRegion(HeapRegion* hr) {
241 if (hr->isHumongous()) {
242 if (hr->startsHumongous()) {
243 oop obj = oop(hr->bottom());
244 if (obj->is_gc_marked()) {
245 obj->forward_to(obj);
246 } else {
247 free_humongous_region(hr);
248 }
249 } else {
250 assert(hr->continuesHumongous(), "Invalid humongous.");
251 }
252 } else {
253 hr->prepare_for_compaction(&_cp);
254 // Also clear the part of the card table that will be unused after
255 // compaction.
256 _mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
257 }
258 return false;
259 }
260 };
262 // Finds the first HeapRegion.
263 class FindFirstRegionClosure: public HeapRegionClosure {
264 HeapRegion* _a_region;
265 public:
266 FindFirstRegionClosure() : _a_region(NULL) {}
267 bool doHeapRegion(HeapRegion* r) {
268 _a_region = r;
269 return true;
270 }
271 HeapRegion* result() { return _a_region; }
272 };
274 void G1MarkSweep::mark_sweep_phase2() {
275 // Now all live objects are marked, compute the new object addresses.
277 // It is imperative that we traverse perm_gen LAST. If dead space is
278 // allowed a range of dead object may get overwritten by a dead int
279 // array. If perm_gen is not traversed last a klassOop may get
280 // overwritten. This is fine since it is dead, but if the class has dead
281 // instances we have to skip them, and in order to find their size we
282 // need the klassOop!
283 //
284 // It is not required that we traverse spaces in the same order in
285 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
286 // tracking expects us to do so. See comment under phase4.
288 G1CollectedHeap* g1h = G1CollectedHeap::heap();
289 Generation* pg = g1h->perm_gen();
291 EventMark m("2 compute new addresses");
292 TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);
293 GenMarkSweep::trace("2");
295 FindFirstRegionClosure cl;
296 g1h->heap_region_iterate(&cl);
297 HeapRegion *r = cl.result();
298 CompactibleSpace* sp = r;
299 if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) {
300 sp = r->next_compaction_space();
301 }
303 G1PrepareCompactClosure blk(sp);
304 g1h->heap_region_iterate(&blk);
305 blk.update_sets();
307 CompactPoint perm_cp(pg, NULL, NULL);
308 pg->prepare_for_compaction(&perm_cp);
309 }
311 class G1AdjustPointersClosure: public HeapRegionClosure {
312 public:
313 bool doHeapRegion(HeapRegion* r) {
314 if (r->isHumongous()) {
315 if (r->startsHumongous()) {
316 // We must adjust the pointers on the single H object.
317 oop obj = oop(r->bottom());
318 debug_only(GenMarkSweep::track_interior_pointers(obj));
319 // point all the oops to the new location
320 obj->adjust_pointers();
321 debug_only(GenMarkSweep::check_interior_pointers());
322 }
323 } else {
324 // This really ought to be "as_CompactibleSpace"...
325 r->adjust_pointers();
326 }
327 return false;
328 }
329 };
331 void G1MarkSweep::mark_sweep_phase3() {
332 G1CollectedHeap* g1h = G1CollectedHeap::heap();
333 Generation* pg = g1h->perm_gen();
335 // Adjust the pointers to reflect the new locations
336 EventMark m("3 adjust pointers");
337 TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);
338 GenMarkSweep::trace("3");
340 SharedHeap* sh = SharedHeap::heap();
342 sh->process_strong_roots(true, // activate StrongRootsScope
343 true, // Collecting permanent generation.
344 SharedHeap::SO_AllClasses,
345 &GenMarkSweep::adjust_root_pointer_closure,
346 NULL, // do not touch code cache here
347 &GenMarkSweep::adjust_pointer_closure);
349 g1h->ref_processor()->weak_oops_do(&GenMarkSweep::adjust_root_pointer_closure);
351 // Now adjust pointers in remaining weak roots. (All of which should
352 // have been cleared if they pointed to non-surviving objects.)
353 g1h->g1_process_weak_roots(&GenMarkSweep::adjust_root_pointer_closure,
354 &GenMarkSweep::adjust_pointer_closure);
356 GenMarkSweep::adjust_marks();
358 G1AdjustPointersClosure blk;
359 g1h->heap_region_iterate(&blk);
360 pg->adjust_pointers();
361 }
363 class G1SpaceCompactClosure: public HeapRegionClosure {
364 public:
365 G1SpaceCompactClosure() {}
367 bool 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->init_mark();
373 } else {
374 assert(hr->is_empty(), "Should have been cleared in phase 2.");
375 }
376 hr->reset_during_compaction();
377 }
378 } else {
379 hr->compact();
380 }
381 return false;
382 }
383 };
385 void G1MarkSweep::mark_sweep_phase4() {
386 // All pointers are now adjusted, move objects accordingly
388 // It is imperative that we traverse perm_gen first in phase4. All
389 // classes must be allocated earlier than their instances, and traversing
390 // perm_gen first makes sure that all klassOops have moved to their new
391 // location before any instance does a dispatch through it's klass!
393 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
394 // in the same order in phase2, phase3 and phase4. We don't quite do that
395 // here (perm_gen first rather than last), so we tell the validate code
396 // to use a higher index (saved from phase2) when verifying perm_gen.
397 G1CollectedHeap* g1h = G1CollectedHeap::heap();
398 Generation* pg = g1h->perm_gen();
400 EventMark m("4 compact heap");
401 TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty);
402 GenMarkSweep::trace("4");
404 pg->compact();
406 G1SpaceCompactClosure blk;
407 g1h->heap_region_iterate(&blk);
409 }
411 // Local Variables: ***
412 // c-indentation-style: gnu ***
413 // End: ***