6755988: G1: assert(new_obj != 0 || ... "should be forwarded")
Summary: A TLAB became large enough to be considered a humongous object allowing multiple objects to be allocated in a humongous region, which violates a basic assumption about humongous regions. The changes ensure that TLABs cannot be regarded as humongous.
Reviewed-by: iveresov, tonyp
--- a/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp Mon Mar 15 02:56:45 2010 -0700
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp Thu Mar 11 11:44:43 2010 -0800
@@ -2102,18 +2102,21 @@
size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
// Return the remaining space in the cur alloc region, but not less than
// the min TLAB size.
- // Also, no more than half the region size, since we can't allow tlabs to
- // grow big enough to accomodate humongous objects.
-
- // We need to story it locally, since it might change between when we
- // test for NULL and when we use it later.
+
+ // Also, this value can be at most the humongous object threshold,
+ // since we can't allow tlabs to grow big enough to accomodate
+ // humongous objects.
+
+ // We need to store the cur alloc region locally, since it might change
+ // between when we test for NULL and when we use it later.
ContiguousSpace* cur_alloc_space = _cur_alloc_region;
+ size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
+
if (cur_alloc_space == NULL) {
- return HeapRegion::GrainBytes/2;
+ return max_tlab_size;
} else {
- return MAX2(MIN2(cur_alloc_space->free(),
- (size_t)(HeapRegion::GrainBytes/2)),
- (size_t)MinTLABSize);
+ return MIN2(MAX2(cur_alloc_space->free(), (size_t)MinTLABSize),
+ max_tlab_size);
}
}
--- a/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp Mon Mar 15 02:56:45 2010 -0700
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp Thu Mar 11 11:44:43 2010 -0800
@@ -1055,7 +1055,12 @@
// Returns "true" iff the given word_size is "very large".
static bool isHumongous(size_t word_size) {
- return word_size >= _humongous_object_threshold_in_words;
+ // Note this has to be strictly greater-than as the TLABs
+ // are capped at the humongous thresold and we want to
+ // ensure that we don't try to allocate a TLAB as
+ // humongous and that we don't allocate a humongous
+ // object in a TLAB.
+ return word_size > _humongous_object_threshold_in_words;
}
// Update mod union table with the set of dirty cards.