8240872: Shenandoah: Avoid updating new regions from start of evacuation
Reviewed-by: shade
diff --git a/src/hotspot/share/gc/shenandoah/shenandoahFreeSet.cpp b/src/hotspot/share/gc/shenandoah/shenandoahFreeSet.cpp
index 43c4d7f..08ca593 100644
--- a/src/hotspot/share/gc/shenandoah/shenandoahFreeSet.cpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahFreeSet.cpp
@@ -184,13 +184,16 @@
// Record actual allocation size
req.set_actual_size(size);
- if (req.is_gc_alloc() && _heap->is_concurrent_traversal_in_progress()) {
- // Traversal needs to traverse through GC allocs. Adjust TAMS to the new top
- // so that these allocations appear below TAMS, and thus get traversed.
- // See top of shenandoahTraversal.cpp for an explanation.
- _heap->marking_context()->capture_top_at_mark_start(r);
- _heap->traversal_gc()->traversal_set()->add_region_check_for_duplicates(r);
- OrderAccess::fence();
+ if (req.is_gc_alloc()) {
+ r->set_update_watermark(r->top());
+ if (_heap->is_concurrent_traversal_in_progress()) {
+ // Traversal needs to traverse through GC allocs. Adjust TAMS to the new top
+ // so that these allocations appear below TAMS, and thus get traversed.
+ // See top of shenandoahTraversal.cpp for an explanation.
+ _heap->marking_context()->capture_top_at_mark_start(r);
+ _heap->traversal_gc()->traversal_set()->add_region_check_for_duplicates(r);
+ OrderAccess::fence();
+ }
}
}
diff --git a/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp b/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp
index cce0461..b778bf4 100644
--- a/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp
@@ -1531,6 +1531,13 @@
verifier()->verify_before_evacuation();
}
+ // Remember limit for updating refs. It's guaranteed that we get no from-space-refs written
+ // from here on.
+ for (uint i = 0; i < num_regions(); i++) {
+ ShenandoahHeapRegion* r = get_region(i);
+ r->set_update_watermark(r->top());
+ }
+
set_evacuation_in_progress(true);
// From here on, we need to update references.
set_has_forwarded_objects(true);
@@ -2391,13 +2398,13 @@
ShenandoahHeapRegion* r = _regions->next();
ShenandoahMarkingContext* const ctx = _heap->complete_marking_context();
while (r != NULL) {
- HeapWord* top_at_start_ur = r->concurrent_iteration_safe_limit();
- assert (top_at_start_ur >= r->bottom(), "sanity");
+ HeapWord* update_watermark = r->get_update_watermark();
+ assert (update_watermark >= r->bottom(), "sanity");
if (r->is_active() && !r->is_cset()) {
- _heap->marked_object_oop_iterate(r, &cl, top_at_start_ur);
+ _heap->marked_object_oop_iterate(r, &cl, update_watermark);
}
if (ShenandoahPacing) {
- _heap->pacer()->report_updaterefs(pointer_delta(top_at_start_ur, r->bottom()));
+ _heap->pacer()->report_updaterefs(pointer_delta(update_watermark, r->bottom()));
}
if (_heap->check_cancelled_gc_and_yield(_concurrent)) {
return;
@@ -2435,10 +2442,6 @@
ShenandoahGCPhase phase(ShenandoahPhaseTimings::init_update_refs_prepare);
make_parsable(true);
- for (uint i = 0; i < num_regions(); i++) {
- ShenandoahHeapRegion* r = get_region(i);
- r->set_concurrent_iteration_safe_limit(r->top());
- }
// Reset iterator.
_update_refs_iterator.reset();
diff --git a/src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.cpp b/src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.cpp
index 6146c18..4af7769 100644
--- a/src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.cpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.cpp
@@ -71,7 +71,8 @@
_seqnum_last_alloc_mutator(0),
_seqnum_last_alloc_gc(0),
_live_data(0),
- _critical_pins(0) {
+ _critical_pins(0),
+ _update_watermark(start) {
ContiguousSpace::initialize(_reserved, true, committed);
}
@@ -479,6 +480,7 @@
reset_alloc_metadata();
_heap->marking_context()->reset_top_at_mark_start(this);
+ set_update_watermark(bottom());
make_empty();
}
diff --git a/src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.hpp b/src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.hpp
index 83cc195..22d2e49 100644
--- a/src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.hpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.hpp
@@ -261,6 +261,8 @@
volatile size_t _live_data;
volatile size_t _critical_pins;
+ HeapWord* _update_watermark;
+
// Claim some space at the end to protect next region
DEFINE_PAD_MINUS_SIZE(0, DEFAULT_CACHE_LINE_SIZE, 0);
@@ -428,6 +430,16 @@
return _seqnum_last_alloc_gc;
}
+ HeapWord* get_update_watermark() const {
+ assert(bottom() <= _update_watermark && _update_watermark <= top(), "within bounds");
+ return _update_watermark;
+ }
+
+ void set_update_watermark(HeapWord* w) {
+ assert(bottom() <= w && w <= top(), "within bounds");
+ _update_watermark = w;
+ }
+
private:
void do_commit();
void do_uncommit();
diff --git a/src/hotspot/share/gc/shenandoah/shenandoahMarkCompact.cpp b/src/hotspot/share/gc/shenandoah/shenandoahMarkCompact.cpp
index 9bc765c..cb43de0 100644
--- a/src/hotspot/share/gc/shenandoah/shenandoahMarkCompact.cpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahMarkCompact.cpp
@@ -224,7 +224,6 @@
void heap_region_do(ShenandoahHeapRegion *r) {
_ctx->capture_top_at_mark_start(r);
r->clear_live_data();
- r->set_concurrent_iteration_safe_limit(r->top());
}
};
