8273476: G1: refine G1CollectedHeap::par_iterate_regions_array_part_from

Reviewed-by: ayang, tschatzl

Author: Hamlin Li

src/hotspot/share/gc/g1/g1CollectedHeap.cpp

@@ -2326,12 +2326,11 @@ void G1CollectedHeap::collection_set_iterate_increment_from(HeapRegionClosure *c
   _collection_set.iterate_incremental_part_from(cl, hr_claimer, worker_id);
 }
 
-void G1CollectedHeap::par_iterate_regions_array_part_from(HeapRegionClosure* cl,
-                                                          HeapRegionClaimer* hr_claimer,
-                                                          const uint* regions,
-                                                          size_t offset,
-                                                          size_t length,
-                                                          uint worker_id) const {
+void G1CollectedHeap::par_iterate_regions_array(HeapRegionClosure* cl,
+                                                HeapRegionClaimer* hr_claimer,
+                                                const uint regions[],
+                                                size_t length,
+                                                uint worker_id) const {
   assert_at_safepoint();
   if (length == 0) {
     return;
@@ -2342,7 +2341,7 @@ void G1CollectedHeap::par_iterate_regions_array_part_from(HeapRegionClosure* cl,
   size_t cur_pos = start_pos;
 
   do {
-    uint region_idx = regions[cur_pos + offset];
+    uint region_idx = regions[cur_pos];
     if (hr_claimer == NULL || hr_claimer->claim_region(region_idx)) {
       HeapRegion* r = region_at(region_idx);
       bool result = cl->do_heap_region(r);

src/hotspot/share/gc/g1/g1CollectedHeap.hpp

@@ -1139,15 +1139,14 @@ class G1CollectedHeap : public CollectedHeap {
     collection_set_iterate_increment_from(blk, NULL, worker_id);
   }
   void collection_set_iterate_increment_from(HeapRegionClosure *blk, HeapRegionClaimer* hr_claimer, uint worker_id);
-  // Iterate part of an array of region indexes given by offset and length, applying
+  // Iterate over the array of region indexes, uint regions[length], applying
   // the given HeapRegionClosure on each region. The worker_id will determine where
-  // in the part to start the iteration to allow for more efficient parallel iteration.
-  void par_iterate_regions_array_part_from(HeapRegionClosure* cl,
-                                           HeapRegionClaimer* hr_claimer,
-                                           const uint* regions,
-                                           size_t offset,
-                                           size_t length,
-                                           uint worker_id) const;
+  // to start the iteration to allow for more efficient parallel iteration.
+  void par_iterate_regions_array(HeapRegionClosure* cl,
+                                 HeapRegionClaimer* hr_claimer,
+                                 const uint regions[],
+                                 size_t length,
+                                 uint worker_id) const;
 
   // Returns the HeapRegion that contains addr. addr must not be NULL.
   template <class T>

src/hotspot/share/gc/g1/g1CollectionSet.cpp

@@ -232,7 +232,11 @@ void G1CollectionSet::iterate_part_from(HeapRegionClosure* cl,
                                         size_t offset,
                                         size_t length,
                                         uint worker_id) const {
-  _g1h->par_iterate_regions_array_part_from(cl, hr_claimer, _collection_set_regions, offset, length, worker_id);
+  _g1h->par_iterate_regions_array(cl,
+                                  hr_claimer,
+                                  &_collection_set_regions[offset],
+                                  length,
+                                  worker_id);
 }
 
 void G1CollectionSet::update_young_region_prediction(HeapRegion* hr,

src/hotspot/share/gc/g1/g1EvacFailureRegions.cpp

@@ -49,12 +49,11 @@ void G1EvacFailureRegions::initialize(uint max_regions) {
 void G1EvacFailureRegions::par_iterate(HeapRegionClosure* closure,
                                        HeapRegionClaimer* _hrclaimer,
                                        uint worker_id) {
-  G1CollectedHeap::heap()->par_iterate_regions_array_part_from(closure,
-                                                               _hrclaimer,
-                                                               _evac_failure_regions,
-                                                               0,
-                                                               Atomic::load(&_evac_failure_regions_cur_length),
-                                                               worker_id);
+  G1CollectedHeap::heap()->par_iterate_regions_array(closure,
+                                                     _hrclaimer,
+                                                     _evac_failure_regions,
+                                                     Atomic::load(&_evac_failure_regions_cur_length),
+                                                     worker_id);
 }
 
 void G1EvacFailureRegions::reset() {