8197569: Refactor eager reclaim for concurrent remembered set rebuilding
Summary: Expose information about eager reclaim region selection.
Reviewed-by: sjohanss, sangheki
--- a/src/hotspot/share/gc/g1/g1CollectedHeap.cpp Mon Mar 26 10:19:31 2018 -0400
+++ b/src/hotspot/share/gc/g1/g1CollectedHeap.cpp Mon Mar 26 16:51:41 2018 +0200
@@ -2583,6 +2583,16 @@
return buffer_size * buffer_num + extra_cards;
}
+bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const {
+ // We don't nominate objects with many remembered set entries, on
+ // the assumption that such objects are likely still live.
+ HeapRegionRemSet* rem_set = r->rem_set();
+
+ return G1EagerReclaimHumongousObjectsWithStaleRefs ?
+ rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) :
+ G1EagerReclaimHumongousObjects && rem_set->is_empty();
+}
+
class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
private:
size_t _total_humongous;
@@ -2590,23 +2600,14 @@
DirtyCardQueue _dcq;
- // We don't nominate objects with many remembered set entries, on
- // the assumption that such objects are likely still live.
- bool is_remset_small(HeapRegion* region) const {
- HeapRegionRemSet* const rset = region->rem_set();
- return G1EagerReclaimHumongousObjectsWithStaleRefs
- ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
- : rset->is_empty();
- }
-
- bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
+ bool humongous_region_is_candidate(G1CollectedHeap* g1h, HeapRegion* region) const {
assert(region->is_starts_humongous(), "Must start a humongous object");
oop obj = oop(region->bottom());
// Dead objects cannot be eager reclaim candidates. Due to class
// unloading it is unsafe to query their classes so we return early.
- if (heap->is_obj_dead(obj, region)) {
+ if (g1h->is_obj_dead(obj, region)) {
return false;
}
@@ -2646,7 +2647,8 @@
// important use case for eager reclaim, and this special handling
// may reduce needed headroom.
- return obj->is_typeArray() && is_remset_small(region);
+ return obj->is_typeArray() &&
+ g1h->is_potential_eager_reclaim_candidate(region);
}
public:
@@ -4818,10 +4820,7 @@
obj->is_typeArray()
);
- // Need to clear mark bit of the humongous object if already set.
- if (next_bitmap->is_marked(r->bottom())) {
- next_bitmap->clear(r->bottom());
- }
+ g1h->concurrent_mark()->humongous_object_eagerly_reclaimed(r);
_humongous_objects_reclaimed++;
do {
HeapRegion* next = g1h->next_region_in_humongous(r);
--- a/src/hotspot/share/gc/g1/g1CollectedHeap.hpp Mon Mar 26 10:19:31 2018 -0400
+++ b/src/hotspot/share/gc/g1/g1CollectedHeap.hpp Mon Mar 26 16:51:41 2018 +0200
@@ -564,6 +564,9 @@
void gc_prologue(bool full);
void gc_epilogue(bool full);
+ // Does the given region fulfill remembered set based eager reclaim candidate requirements?
+ bool is_potential_eager_reclaim_candidate(HeapRegion* r) const;
+
// Modify the reclaim candidate set and test for presence.
// These are only valid for starts_humongous regions.
inline void set_humongous_reclaim_candidate(uint region, bool value);
--- a/src/hotspot/share/gc/g1/g1ConcurrentMark.cpp Mon Mar 26 10:19:31 2018 -0400
+++ b/src/hotspot/share/gc/g1/g1ConcurrentMark.cpp Mon Mar 26 16:51:41 2018 +0200
@@ -515,6 +515,14 @@
set_concurrent_marking_in_progress();
}
+void G1ConcurrentMark::humongous_object_eagerly_reclaimed(HeapRegion* r) {
+ assert(SafepointSynchronize::is_at_safepoint(), "May only be called at a safepoint.");
+
+ // Need to clear mark bit of the humongous object if already set and during a marking cycle.
+ if (_next_mark_bitmap->is_marked(r->bottom())) {
+ _next_mark_bitmap->clear(r->bottom());
+ }
+}
void G1ConcurrentMark::reset_marking_state() {
_global_mark_stack.set_empty();
--- a/src/hotspot/share/gc/g1/g1ConcurrentMark.hpp Mon Mar 26 10:19:31 2018 -0400
+++ b/src/hotspot/share/gc/g1/g1ConcurrentMark.hpp Mon Mar 26 16:51:41 2018 +0200
@@ -447,6 +447,8 @@
// true, periodically insert checks to see if this method should exit prematurely.
void clear_bitmap(G1CMBitMap* bitmap, WorkGang* workers, bool may_yield);
public:
+ // Notification for eagerly reclaimed regions to clean up.
+ void humongous_object_eagerly_reclaimed(HeapRegion* r);
// Manipulation of the global mark stack.
// The push and pop operations are used by tasks for transfers
// between task-local queues and the global mark stack.