Thu, 20 Oct 2011 12:06:20 -0700
7099824: G1: we should take the pending list lock before doing the remark pause
Summary: Acquire the pending list lock in the prologue method of G1's concurrent VM_Operation and release the lock in the epilogue() method. The locking/unlocking order of the pending list lock and the Heap_lock should match that in the prologue and epilogue methods of VM_GC_Operation.
Reviewed-by: tonyp, ysr
1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Precondition");
67 GenMarkSweep::_ref_processor = rp;
68 rp->setup_policy(clear_all_softrefs);
70 // When collecting the permanent generation methodOops may be moving,
71 // so we either have to flush all bcp data or convert it into bci.
72 CodeCache::gc_prologue();
73 Threads::gc_prologue();
75 // Increment the invocation count for the permanent generation, since it is
76 // implicitly collected whenever we do a full mark sweep collection.
77 sh->perm_gen()->stat_record()->invocations++;
79 bool marked_for_unloading = false;
81 allocate_stacks();
83 // We should save the marks of the currently locked biased monitors.
84 // The marking doesn't preserve the marks of biased objects.
85 BiasedLocking::preserve_marks();
87 mark_sweep_phase1(marked_for_unloading, clear_all_softrefs);
89 mark_sweep_phase2();
91 // Don't add any more derived pointers during phase3
92 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
94 mark_sweep_phase3();
96 mark_sweep_phase4();
98 GenMarkSweep::restore_marks();
99 BiasedLocking::restore_marks();
100 GenMarkSweep::deallocate_stacks();
102 // We must invalidate the perm-gen rs, so that it gets rebuilt.
103 GenRemSet* rs = sh->rem_set();
104 rs->invalidate(sh->perm_gen()->used_region(), true /*whole_heap*/);
106 // "free at last gc" is calculated from these.
107 // CHF: cheating for now!!!
108 // Universe::set_heap_capacity_at_last_gc(Universe::heap()->capacity());
109 // Universe::set_heap_used_at_last_gc(Universe::heap()->used());
111 Threads::gc_epilogue();
112 CodeCache::gc_epilogue();
113 JvmtiExport::gc_epilogue();
115 // refs processing: clean slate
116 GenMarkSweep::_ref_processor = NULL;
117 }
120 void G1MarkSweep::allocate_stacks() {
121 GenMarkSweep::_preserved_count_max = 0;
122 GenMarkSweep::_preserved_marks = NULL;
123 GenMarkSweep::_preserved_count = 0;
124 }
126 void G1MarkSweep::mark_sweep_phase1(bool& marked_for_unloading,
127 bool clear_all_softrefs) {
128 // Recursively traverse all live objects and mark them
129 EventMark m("1 mark object");
130 TraceTime tm("phase 1", PrintGC && Verbose, true, gclog_or_tty);
131 GenMarkSweep::trace(" 1");
133 SharedHeap* sh = SharedHeap::heap();
135 sh->process_strong_roots(true, // activeate StrongRootsScope
136 true, // Collecting permanent generation.
137 SharedHeap::SO_SystemClasses,
138 &GenMarkSweep::follow_root_closure,
139 &GenMarkSweep::follow_code_root_closure,
140 &GenMarkSweep::follow_root_closure);
142 // Process reference objects found during marking
143 ReferenceProcessor* rp = GenMarkSweep::ref_processor();
144 assert(rp == G1CollectedHeap::heap()->ref_processor_stw(), "Sanity");
146 rp->setup_policy(clear_all_softrefs);
147 rp->process_discovered_references(&GenMarkSweep::is_alive,
148 &GenMarkSweep::keep_alive,
149 &GenMarkSweep::follow_stack_closure,
150 NULL);
152 // Follow system dictionary roots and unload classes
153 bool purged_class = SystemDictionary::do_unloading(&GenMarkSweep::is_alive);
154 assert(GenMarkSweep::_marking_stack.is_empty(),
155 "stack should be empty by now");
157 // Follow code cache roots (has to be done after system dictionary,
158 // assumes all live klasses are marked)
159 CodeCache::do_unloading(&GenMarkSweep::is_alive,
160 &GenMarkSweep::keep_alive,
161 purged_class);
162 GenMarkSweep::follow_stack();
164 // Update subklass/sibling/implementor links of live klasses
165 GenMarkSweep::follow_weak_klass_links();
166 assert(GenMarkSweep::_marking_stack.is_empty(),
167 "stack should be empty by now");
169 // Visit memoized MDO's and clear any unmarked weak refs
170 GenMarkSweep::follow_mdo_weak_refs();
171 assert(GenMarkSweep::_marking_stack.is_empty(), "just drained");
173 // Visit interned string tables and delete unmarked oops
174 StringTable::unlink(&GenMarkSweep::is_alive);
175 // Clean up unreferenced symbols in symbol table.
176 SymbolTable::unlink();
178 assert(GenMarkSweep::_marking_stack.is_empty(),
179 "stack should be empty by now");
181 if (VerifyDuringGC) {
182 HandleMark hm; // handle scope
183 COMPILER2_PRESENT(DerivedPointerTableDeactivate dpt_deact);
184 gclog_or_tty->print(" VerifyDuringGC:(full)[Verifying ");
185 Universe::heap()->prepare_for_verify();
186 // Note: we can verify only the heap here. When an object is
187 // marked, the previous value of the mark word (including
188 // identity hash values, ages, etc) is preserved, and the mark
189 // word is set to markOop::marked_value - effectively removing
190 // any hash values from the mark word. These hash values are
191 // used when verifying the dictionaries and so removing them
192 // from the mark word can make verification of the dictionaries
193 // fail. At the end of the GC, the orginal mark word values
194 // (including hash values) are restored to the appropriate
195 // objects.
196 Universe::heap()->verify(/* allow dirty */ true,
197 /* silent */ false,
198 /* option */ VerifyOption_G1UseMarkWord);
200 G1CollectedHeap* g1h = G1CollectedHeap::heap();
201 gclog_or_tty->print_cr("]");
202 }
203 }
205 class G1PrepareCompactClosure: public HeapRegionClosure {
206 G1CollectedHeap* _g1h;
207 ModRefBarrierSet* _mrbs;
208 CompactPoint _cp;
209 HumongousRegionSet _humongous_proxy_set;
211 void free_humongous_region(HeapRegion* hr) {
212 HeapWord* end = hr->end();
213 size_t dummy_pre_used;
214 FreeRegionList dummy_free_list("Dummy Free List for G1MarkSweep");
216 assert(hr->startsHumongous(),
217 "Only the start of a humongous region should be freed.");
218 _g1h->free_humongous_region(hr, &dummy_pre_used, &dummy_free_list,
219 &_humongous_proxy_set, false /* par */);
220 hr->prepare_for_compaction(&_cp);
221 // Also clear the part of the card table that will be unused after
222 // compaction.
223 _mrbs->clear(MemRegion(hr->compaction_top(), end));
224 dummy_free_list.remove_all();
225 }
227 public:
228 G1PrepareCompactClosure(CompactibleSpace* cs)
229 : _g1h(G1CollectedHeap::heap()),
230 _mrbs(G1CollectedHeap::heap()->mr_bs()),
231 _cp(NULL, cs, cs->initialize_threshold()),
232 _humongous_proxy_set("G1MarkSweep Humongous Proxy Set") { }
234 void update_sets() {
235 // We'll recalculate total used bytes and recreate the free list
236 // at the end of the GC, so no point in updating those values here.
237 _g1h->update_sets_after_freeing_regions(0, /* pre_used */
238 NULL, /* free_list */
239 &_humongous_proxy_set,
240 false /* par */);
241 }
243 bool doHeapRegion(HeapRegion* hr) {
244 if (hr->isHumongous()) {
245 if (hr->startsHumongous()) {
246 oop obj = oop(hr->bottom());
247 if (obj->is_gc_marked()) {
248 obj->forward_to(obj);
249 } else {
250 free_humongous_region(hr);
251 }
252 } else {
253 assert(hr->continuesHumongous(), "Invalid humongous.");
254 }
255 } else {
256 hr->prepare_for_compaction(&_cp);
257 // Also clear the part of the card table that will be unused after
258 // compaction.
259 _mrbs->clear(MemRegion(hr->compaction_top(), hr->end()));
260 }
261 return false;
262 }
263 };
265 // Finds the first HeapRegion.
266 class FindFirstRegionClosure: public HeapRegionClosure {
267 HeapRegion* _a_region;
268 public:
269 FindFirstRegionClosure() : _a_region(NULL) {}
270 bool doHeapRegion(HeapRegion* r) {
271 _a_region = r;
272 return true;
273 }
274 HeapRegion* result() { return _a_region; }
275 };
277 void G1MarkSweep::mark_sweep_phase2() {
278 // Now all live objects are marked, compute the new object addresses.
280 // It is imperative that we traverse perm_gen LAST. If dead space is
281 // allowed a range of dead object may get overwritten by a dead int
282 // array. If perm_gen is not traversed last a klassOop may get
283 // overwritten. This is fine since it is dead, but if the class has dead
284 // instances we have to skip them, and in order to find their size we
285 // need the klassOop!
286 //
287 // It is not required that we traverse spaces in the same order in
288 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
289 // tracking expects us to do so. See comment under phase4.
291 G1CollectedHeap* g1h = G1CollectedHeap::heap();
292 Generation* pg = g1h->perm_gen();
294 EventMark m("2 compute new addresses");
295 TraceTime tm("phase 2", PrintGC && Verbose, true, gclog_or_tty);
296 GenMarkSweep::trace("2");
298 FindFirstRegionClosure cl;
299 g1h->heap_region_iterate(&cl);
300 HeapRegion *r = cl.result();
301 CompactibleSpace* sp = r;
302 if (r->isHumongous() && oop(r->bottom())->is_gc_marked()) {
303 sp = r->next_compaction_space();
304 }
306 G1PrepareCompactClosure blk(sp);
307 g1h->heap_region_iterate(&blk);
308 blk.update_sets();
310 CompactPoint perm_cp(pg, NULL, NULL);
311 pg->prepare_for_compaction(&perm_cp);
312 }
314 class G1AdjustPointersClosure: public HeapRegionClosure {
315 public:
316 bool doHeapRegion(HeapRegion* r) {
317 if (r->isHumongous()) {
318 if (r->startsHumongous()) {
319 // We must adjust the pointers on the single H object.
320 oop obj = oop(r->bottom());
321 debug_only(GenMarkSweep::track_interior_pointers(obj));
322 // point all the oops to the new location
323 obj->adjust_pointers();
324 debug_only(GenMarkSweep::check_interior_pointers());
325 }
326 } else {
327 // This really ought to be "as_CompactibleSpace"...
328 r->adjust_pointers();
329 }
330 return false;
331 }
332 };
334 void G1MarkSweep::mark_sweep_phase3() {
335 G1CollectedHeap* g1h = G1CollectedHeap::heap();
336 Generation* pg = g1h->perm_gen();
338 // Adjust the pointers to reflect the new locations
339 EventMark m("3 adjust pointers");
340 TraceTime tm("phase 3", PrintGC && Verbose, true, gclog_or_tty);
341 GenMarkSweep::trace("3");
343 SharedHeap* sh = SharedHeap::heap();
345 sh->process_strong_roots(true, // activate StrongRootsScope
346 true, // Collecting permanent generation.
347 SharedHeap::SO_AllClasses,
348 &GenMarkSweep::adjust_root_pointer_closure,
349 NULL, // do not touch code cache here
350 &GenMarkSweep::adjust_pointer_closure);
352 assert(GenMarkSweep::ref_processor() == g1h->ref_processor_stw(), "Sanity");
353 g1h->ref_processor_stw()->weak_oops_do(&GenMarkSweep::adjust_root_pointer_closure);
355 // Now adjust pointers in remaining weak roots. (All of which should
356 // have been cleared if they pointed to non-surviving objects.)
357 g1h->g1_process_weak_roots(&GenMarkSweep::adjust_root_pointer_closure,
358 &GenMarkSweep::adjust_pointer_closure);
360 GenMarkSweep::adjust_marks();
362 G1AdjustPointersClosure blk;
363 g1h->heap_region_iterate(&blk);
364 pg->adjust_pointers();
365 }
367 class G1SpaceCompactClosure: public HeapRegionClosure {
368 public:
369 G1SpaceCompactClosure() {}
371 bool 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->init_mark();
377 } else {
378 assert(hr->is_empty(), "Should have been cleared in phase 2.");
379 }
380 hr->reset_during_compaction();
381 }
382 } else {
383 hr->compact();
384 }
385 return false;
386 }
387 };
389 void G1MarkSweep::mark_sweep_phase4() {
390 // All pointers are now adjusted, move objects accordingly
392 // It is imperative that we traverse perm_gen first in phase4. All
393 // classes must be allocated earlier than their instances, and traversing
394 // perm_gen first makes sure that all klassOops have moved to their new
395 // location before any instance does a dispatch through it's klass!
397 // The ValidateMarkSweep live oops tracking expects us to traverse spaces
398 // in the same order in phase2, phase3 and phase4. We don't quite do that
399 // here (perm_gen first rather than last), so we tell the validate code
400 // to use a higher index (saved from phase2) when verifying perm_gen.
401 G1CollectedHeap* g1h = G1CollectedHeap::heap();
402 Generation* pg = g1h->perm_gen();
404 EventMark m("4 compact heap");
405 TraceTime tm("phase 4", PrintGC && Verbose, true, gclog_or_tty);
406 GenMarkSweep::trace("4");
408 pg->compact();
410 G1SpaceCompactClosure blk;
411 g1h->heap_region_iterate(&blk);
413 }
415 // Local Variables: ***
416 // c-indentation-style: gnu ***
417 // End: ***