truffle: src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp comparison

comparison src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp @ 352:e0c09f7ec5c4

6702387: G1: assertion failure: assert(p == current_top || oop(p)->is_oop(),"p is not a block start") Summary: Do not coalesce dead and moved objects when removing self-forwarding pointers during the evacuation failure. Also fixed a issue in a BOT refinement code for TLABs. Reviewed-by: tonyp, jcoomes

author	iveresov
date	Thu, 03 Jul 2008 03:17:29 -0700
parents	37f87013dfd8
children	9bb2c10ac07b

comparison

equal deleted inserted replaced

-:fab5f738c515
+:e0c09f7ec5c4
 class RemoveSelfPointerClosure: public ObjectClosure {
 private:
 G1CollectedHeap* _g1;
 ConcurrentMark* _cm;
 HeapRegion* _hr;
-HeapWord* _last_self_forwarded_end;
 size_t _prev_marked_bytes;
 size_t _next_marked_bytes;
 public:
 RemoveSelfPointerClosure(G1CollectedHeap* g1, HeapRegion* hr) :
 _g1(g1), _cm(_g1->concurrent_mark()), _hr(hr),
-_last_self_forwarded_end(_hr->bottom()),
 _prev_marked_bytes(0), _next_marked_bytes(0)
 {}
 size_t prev_marked_bytes() { return _prev_marked_bytes; }
 size_t next_marked_bytes() { return _next_marked_bytes; }
-void fill_remainder() {
+// The original idea here was to coalesce evacuated and dead objects.
-HeapWord* limit = _hr->top();
+// However that caused complications with the block offset table (BOT).
-MemRegion mr(_last_self_forwarded_end, limit);
+// In particular if there were two TLABs, one of them partially refined.
-if (!mr.is_empty()) {
+// |----- TLAB_1--------|----TLAB_2-~~~(partially refined part)~~~|
+// The BOT entries of the unrefined part of TLAB_2 point to the start
+// of TLAB_2. If the last object of the TLAB_1 and the first object
+// of TLAB_2 are coalesced, then the cards of the unrefined part
+// would point into middle of the filler object.
+//
+// The current approach is to not coalesce and leave the BOT contents intact.
+void do_object(oop obj) {
+if (obj->is_forwarded() && obj->forwardee() == obj) {
+// The object failed to move.
+assert(!_g1->is_obj_dead(obj), "We should not be preserving dead objs.");
+_cm->markPrev(obj);
+assert(_cm->isPrevMarked(obj), "Should be marked!");
+_prev_marked_bytes += (obj->size() * HeapWordSize);
+if (_g1->mark_in_progress() && !_g1->is_obj_ill(obj)) {
+_cm->markAndGrayObjectIfNecessary(obj);
+}
+obj->set_mark(markOopDesc::prototype());
+// While we were processing RSet buffers during the
+// collection, we actually didn't scan any cards on the
+// collection set, since we didn't want to update remebered
+// sets with entries that point into the collection set, given
+// that live objects fromthe collection set are about to move
+// and such entries will be stale very soon. This change also
+// dealt with a reliability issue which involved scanning a
+// card in the collection set and coming across an array that
+// was being chunked and looking malformed. The problem is
+// that, if evacuation fails, we might have remembered set
+// entries missing given that we skipped cards on the
+// collection set. So, we'll recreate such entries now.
+RecreateRSetEntriesClosure cl(_g1, _hr);
+obj->oop_iterate(&cl);
+assert(_cm->isPrevMarked(obj), "Should be marked!");
+} else {
+// The object has been either evacuated or is dead. Fill it with a
+// dummy object.
+MemRegion mr((HeapWord*)obj, obj->size());
 SharedHeap::fill_region_with_object(mr);
 _cm->clearRangeBothMaps(mr);
-_hr->declare_filled_region_to_BOT(mr);
-}
-}
-void do_object(oop obj) {
-if (obj->is_forwarded()) {
-if (obj->forwardee() == obj) {
-assert(!_g1->is_obj_dead(obj), "We should not be preserving dead objs.");
-_cm->markPrev(obj);
-assert(_cm->isPrevMarked(obj), "Should be marked!");
-_prev_marked_bytes += (obj->size() * HeapWordSize);
-if (_g1->mark_in_progress() && !_g1->is_obj_ill(obj)) {
-_cm->markAndGrayObjectIfNecessary(obj);
-}
-HeapWord* obj_start = (HeapWord*)obj;
-if (obj_start > _last_self_forwarded_end) {
-MemRegion mr(_last_self_forwarded_end, obj_start);
-SharedHeap::fill_region_with_object(mr);
-assert(_cm->isPrevMarked(obj), "Should be marked!");
-_cm->clearRangeBothMaps(mr);
-assert(_cm->isPrevMarked(obj), "Should be marked!");
-_hr->declare_filled_region_to_BOT(mr);
-}
-_last_self_forwarded_end = obj_start + obj->size();
-obj->set_mark(markOopDesc::prototype());
-// While we were processing RSet buffers during the
-// collection, we actually didn't scan any cards on the
-// collection set, since we didn't want to update remebered
-// sets with entries that point into the collection set, given
-// that live objects fromthe collection set are about to move
-// and such entries will be stale very soon. This change also
-// dealt with a reliability issue which involved scanning a
-// card in the collection set and coming across an array that
-// was being chunked and looking malformed. The problem is
-// that, if evacuation fails, we might have remembered set
-// entries missing given that we skipped cards on the
-// collection set. So, we'll recreate such entries now.
-RecreateRSetEntriesClosure cl(_g1, _hr);
-obj->oop_iterate(&cl);
-assert(_cm->isPrevMarked(obj), "Should be marked!");
-}
 }
 }
 };
 void G1CollectedHeap::remove_self_forwarding_pointers() {
 if (cur->evacuation_failed()) {
 RemoveSelfPointerClosure rspc(_g1h, cur);
 assert(cur->in_collection_set(), "bad CS");
 cur->object_iterate(&rspc);
-rspc.fill_remainder();
 // A number of manipulations to make the TAMS be the current top,
 // and the marked bytes be the ones observed in the iteration.
 if (_g1h->concurrent_mark()->at_least_one_mark_complete()) {
 // The comments below are the postconditions achieved by the

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comparison src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp @ 352:e0c09f7ec5c4