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8069760: When iterating over a card, G1 often iterates over much more references than are contained in the card

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Properly bound the iteration work for objArray-oops.

Reviewed-by: mgerdin, kbarrett
This commit is contained in:
Thomas Schatzl 2015-02-02 10:38:39 +01:00
parent 1a1ddd0d4b
commit ba4a04aa05
1 changed files with 15 additions and 22 deletions
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37
hotspot/src/share/vm/gc_implementation/g1/heapRegion.cpp
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@ -420,7 +420,7 @@ oops_on_card_seq_iterate_careful(MemRegion mr,
oop obj;
HeapWord* next = cur;
while (next <= start) {
do {
cur = next;
obj = oop(cur);
if (obj->klass_or_null() == NULL) {
@ -429,45 +429,38 @@ oops_on_card_seq_iterate_careful(MemRegion mr,
}
// 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(obj == oop(cur), "sanity");
assert(cur <= start, "Loop postcondition");
assert(obj->klass_or_null() != NULL, "Loop postcondition");
assert((cur + block_size(cur)) > start, "Loop postcondition");
if (!g1h->is_obj_dead(obj)) {
obj->oop_iterate(cl, mr);
}
while (cur < end) {
do {
obj = oop(cur);
assert((cur + block_size(cur)) > (HeapWord*)obj, "Loop invariant");
if (obj->klass_or_null() == NULL) {
// Ran into an unparseable point.
return cur;
};
}
// Otherwise:
next = cur + block_size(cur);
// Advance the current pointer. "obj" still points to the object to iterate.
cur = cur + block_size(cur);
if (!g1h->is_obj_dead(obj)) {
if (next < end || !obj->is_objArray()) {
// This object either does not span the MemRegion
// boundary, or if it does it's not an array.
// Apply closure to whole object.
// 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.
if (!obj->is_objArray() || (((HeapWord*)obj) >= start && cur <= end)) {
obj->oop_iterate(cl);
} else {
// This obj is an array that spans the boundary.
// Stop at the boundary.
obj->oop_iterate(cl, mr);
}
}
cur = next;
}
} while (cur < end);
return NULL;
}