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src/share/vm/gc/g1/heapRegion.cpp
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rev 12058 : [mq]: specialize
rev 12059 : [mq]: no_requeue
@@ -350,11 +350,50 @@
"marked: " SIZE_FORMAT " used: " SIZE_FORMAT, marked_bytes, used());
_prev_top_at_mark_start = top();
_prev_marked_bytes = marked_bytes;
}
-bool HeapRegion::oops_on_card_seq_iterate_careful(MemRegion mr,
+// Humongous objects are allocated directly in the old-gen. Need
+// special handling for concurrent processing encountering an
+// in-progress allocation.
+static void do_oops_on_card_in_humongous(MemRegion mr,
+ FilterOutOfRegionClosure* cl,
+ HeapRegion* hr,
+ G1CollectedHeap* g1h) {
+ assert(hr->is_humongous(), "precondition");
+ HeapRegion* sr = hr->humongous_start_region();
+ oop obj = oop(sr->bottom());
+
+ // If concurrent and klass_or_null is NULL, then space has been
+ // allocated but the object has not yet been published by setting
+ // the klass. That can only happen if the card is stale, since
+ // there can't have been object stores into the incomplete object.
+ // In that case, we can ignore the card.
+ if (g1h->is_gc_active() || (obj->klass_or_null_acquire() != NULL)) {
+ // Only filler objects follow a humongous object in the containing
+ // regions, and we can ignore those. So only process the one
+ // humongous object.
+ if (!g1h->is_obj_dead(obj, sr)) {
+ if (obj->is_objArray() || (sr->bottom() < mr.start())) {
+ // objArrays are always marked precisely, so limit processing
+ // with mr. Non-objArrays might be precisely marked, and since
+ // it's humongous it's worthwhile avoiding full processing.
+ // However, the card could be stale and only cover filler
+ // objects. That should be rare, so not worth checking for;
+ // instead let it fall out from the bounded iteration.
+ obj->oop_iterate(cl, mr);
+ } else {
+ // If obj is not an objArray and mr contains the start of the
+ // obj, then this could be an imprecise mark, and we need to
+ // process the entire object.
+ obj->oop_iterate(cl);
+ }
+ }
+ }
+}
+
+void HeapRegion::oops_on_card_seq_iterate_careful(MemRegion mr,
FilterOutOfRegionClosure* cl,
jbyte* card_ptr) {
assert(card_ptr != NULL, "pre-condition");
G1CollectedHeap* g1h = G1CollectedHeap::heap();
@@ -365,87 +404,82 @@
mr = mr.intersection(MemRegion(bottom(), scan_top()));
} else {
mr = mr.intersection(used_region());
}
if (mr.is_empty()) {
- return true;
+ return;
}
// Otherwise, find the obj that extends onto mr.start().
// The intersection of the incoming mr (for the card) and the
// allocated part of the region is non-empty. This implies that
// we have actually allocated into this region. The code in
// G1CollectedHeap.cpp that allocates a new region sets the
// is_young tag on the region before allocating. Thus we
// safely know if this region is young.
if (is_young()) {
- return true;
+ return;
}
// We can only clean the card here, after we make the decision that
// the card is not young.
*card_ptr = CardTableModRefBS::clean_card_val();
// We must complete this write before we do any of the reads below.
OrderAccess::storeload();
+ // Special handling for humongous regions.
+ if (is_humongous()) {
+ return do_oops_on_card_in_humongous(mr, cl, this, g1h);
+ }
+
+ // During GC we limit mr by scan_top. So we never get here with an
+ // mr covering objects allocated during GC. Non-humongous objects
+ // only reach the old-gen during GC. So the parts of the heap that
+ // may be examined here are always parsable; there's no need to use
+ // klass_or_null here to detect in-progress allocations.
+
// Cache the boundaries of the memory region in some const locals
HeapWord* const start = mr.start();
HeapWord* const end = mr.end();
- // Update BOT as needed while finding start of (potential) object.
+ // Update BOT as needed while finding start of (possibly dead)
+ // object containing the start of the region.
HeapWord* cur = block_start(start);
- assert(cur <= start, "Postcondition");
-
- oop obj;
- HeapWord* next = cur;
- do {
- cur = next;
- obj = oop(cur);
- if (obj->klass_or_null() == NULL) {
- // Ran into an unparseable point.
- assert(!g1h->is_gc_active(),
- "Unparsable heap during GC at " PTR_FORMAT, p2i(cur));
- return false;
- }
- // Otherwise...
- next = cur + block_size(cur);
- } while (next <= start);
-
- // If we finish the above loop...We have a parseable object that
- // begins on or before the start of the memory region, and ends
- // inside or spans the entire region.
- assert(cur <= start, "Loop postcondition");
- assert(obj->klass_or_null() != NULL, "Loop postcondition");
+#ifdef ASSERT
+ {
+ assert(cur <= start,
+ "cur: " PTR_FORMAT ", start: " PTR_FORMAT, p2i(cur), p2i(start));
+ HeapWord* next = cur + block_size(cur);
+ assert(start < next,
+ "start: " PTR_FORMAT ", next: " PTR_FORMAT, p2i(start), p2i(next));
+ }
+#endif
do {
- obj = oop(cur);
- assert((cur + block_size(cur)) > (HeapWord*)obj, "Loop invariant");
- if (obj->klass_or_null() == NULL) {
- // Ran into an unparseable point.
- assert(!g1h->is_gc_active(),
- "Unparsable heap during GC at " PTR_FORMAT, p2i(cur));
- return false;
- }
-
- // Advance the current pointer. "obj" still points to the object to iterate.
- cur = cur + block_size(cur);
-
- if (!g1h->is_obj_dead(obj)) {
- // Non-objArrays are sometimes marked imprecise at the object start. We
- // always need to iterate over them in full.
- // We only iterate over object arrays in full if they are completely contained
- // in the memory region.
+ oop obj = oop(cur);
+ assert(obj->is_oop(true), "Not an oop at " PTR_FORMAT, p2i(cur));
+ assert(obj->klass_or_null() != NULL,
+ "Unparsable heap at " PTR_FORMAT, p2i(cur));
+
+ if (g1h->is_obj_dead(obj, this)) {
+ // Carefully step over dead object.
+ cur += block_size(cur);
+ } else {
+ // Step over live object, and process its references.
+ cur += obj->size();
+ // Non-objArrays are usually marked imprecise at the object
+ // start, in which case we need to iterate over them in full.
+ // objArrays are precisely marked, but can still be iterated
+ // over in full if completely covered.
if (!obj->is_objArray() || (((HeapWord*)obj) >= start && cur <= end)) {
obj->oop_iterate(cl);
} else {
obj->oop_iterate(cl, mr);
}
}
} while (cur < end);
-
- return true;
}
// Code roots support
void HeapRegion::add_strong_code_root(nmethod* nm) {
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