8375971: G1: Convert G1EvacStats to use Atomic<T>

Reviewed-by: iwalulya, kbarrett

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

@@ -31,6 +31,7 @@
 #include "gc/g1/g1CollectorState.hpp"
 #include "gc/g1/g1ConcurrentMark.inline.hpp"
 #include "gc/g1/g1EvacFailureRegions.hpp"
+#include "gc/g1/g1EvacStats.inline.hpp"
 #include "gc/g1/g1HeapRegion.inline.hpp"
 #include "gc/g1/g1HeapRegionManager.inline.hpp"
 #include "gc/g1/g1HeapRegionRemSet.hpp"

src/hotspot/share/gc/g1/g1EvacStats.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2026, 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
@@ -22,13 +22,24 @@
  *
  */
 
-#include "gc/g1/g1EvacStats.hpp"
+#include "gc/g1/g1EvacStats.inline.hpp"
 #include "gc/shared/gc_globals.hpp"
 #include "gc/shared/gcId.hpp"
 #include "logging/log.hpp"
 #include "memory/allocation.inline.hpp"
 #include "runtime/globals.hpp"
 
+void G1EvacStats::reset() {
+  PLABStats::reset();
+  _region_end_waste.store_relaxed(0);
+  _regions_filled.store_relaxed(0);
+  _num_plab_filled.store_relaxed(0);
+  _direct_allocated.store_relaxed(0);
+  _num_direct_allocated.store_relaxed(0);
+  _failure_used.store_relaxed(0);
+  _failure_waste.store_relaxed(0);
+}
+
 void G1EvacStats::log_plab_allocation() {
   log_debug(gc, plab)("%s PLAB allocation: "
                       "allocated: %zuB, "
@@ -51,13 +62,13 @@ void G1EvacStats::log_plab_allocation() {
                       "failure used: %zuB, "
                       "failure wasted: %zuB",
                       _description,
-                      _region_end_waste * HeapWordSize,
-                      _regions_filled,
-                      _num_plab_filled,
-                      _direct_allocated * HeapWordSize,
-                      _num_direct_allocated,
-                      _failure_used * HeapWordSize,
-                      _failure_waste * HeapWordSize);
+                      region_end_waste() * HeapWordSize,
+                      regions_filled(),
+                      num_plab_filled(),
+                      direct_allocated() * HeapWordSize,
+                      num_direct_allocated(),
+                      failure_used() * HeapWordSize,
+                      failure_waste() * HeapWordSize);
 }
 
 void G1EvacStats::log_sizing(size_t calculated_words, size_t net_desired_words) {
@@ -109,7 +120,7 @@ size_t G1EvacStats::compute_desired_plab_size() const {
   // threads do not allocate anything but a few rather large objects. In this
   // degenerate case the PLAB size would simply quickly tend to minimum PLAB size,
   // which is an okay reaction.
-  size_t const used_for_waste_calculation = used() > _region_end_waste ? used() - _region_end_waste : 0;
+  size_t const used_for_waste_calculation = used() > region_end_waste() ? used() - region_end_waste() : 0;
 
   size_t const total_waste_allowed = used_for_waste_calculation * TargetPLABWastePct;
   return (size_t)((double)total_waste_allowed / (100 - G1LastPLABAverageOccupancy));

src/hotspot/share/gc/g1/g1EvacStats.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2026, 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
@@ -27,6 +27,7 @@
 
 #include "gc/shared/gcUtil.hpp"
 #include "gc/shared/plab.hpp"
+#include "runtime/atomic.hpp"
 
 // Records various memory allocation statistics gathered during evacuation. All sizes
 // are in HeapWords.
@@ -36,30 +37,21 @@ class G1EvacStats : public PLABStats {
   AdaptiveWeightedAverage
          _net_plab_size_filter;  // Integrator with decay
 
-  size_t _region_end_waste; // Number of words wasted due to skipping to the next region.
-  uint   _regions_filled;   // Number of regions filled completely.
-  size_t _num_plab_filled; // Number of PLABs filled and retired.
-  size_t _direct_allocated; // Number of words allocated directly into the regions.
-  size_t _num_direct_allocated; // Number of direct allocation attempts.
+  Atomic<size_t> _region_end_waste; // Number of words wasted due to skipping to the next region.
+  Atomic<uint>   _regions_filled;   // Number of regions filled completely.
+  Atomic<size_t> _num_plab_filled; // Number of PLABs filled and retired.
+  Atomic<size_t> _direct_allocated; // Number of words allocated directly into the regions.
+  Atomic<size_t> _num_direct_allocated; // Number of direct allocation attempts.
 
   // Number of words in live objects remaining in regions that ultimately suffered an
   // evacuation failure. This is used in the regions when the regions are made old regions.
-  size_t _failure_used;
+  Atomic<size_t> _failure_used;
   // Number of words wasted in regions which failed evacuation. This is the sum of space
   // for objects successfully copied out of the regions (now dead space) plus waste at the
   // end of regions.
-  size_t _failure_waste;
+  Atomic<size_t> _failure_waste;
 
-  virtual void reset() {
-    PLABStats::reset();
-    _region_end_waste = 0;
-    _regions_filled = 0;
-    _num_plab_filled = 0;
-    _direct_allocated = 0;
-    _num_direct_allocated = 0;
-    _failure_used = 0;
-    _failure_waste = 0;
-  }
+  virtual void reset();
 
   void log_plab_allocation();
   void log_sizing(size_t calculated_words, size_t net_desired_words);
@@ -77,16 +69,16 @@ public:
   // Should be called at the end of a GC pause.
   void adjust_desired_plab_size();
 
-  uint regions_filled() const { return _regions_filled; }
-  size_t num_plab_filled() const { return _num_plab_filled; }
-  size_t region_end_waste() const { return _region_end_waste; }
-  size_t direct_allocated() const { return _direct_allocated; }
-  size_t num_direct_allocated() const { return _num_direct_allocated; }
+  uint regions_filled() const;
+  size_t num_plab_filled() const;
+  size_t region_end_waste() const;
+  size_t direct_allocated() const;
+  size_t num_direct_allocated() const;
 
   // Amount of space in heapwords used in the failing regions when an evacuation failure happens.
-  size_t failure_used() const { return _failure_used; }
+  size_t failure_used() const;
   // Amount of space in heapwords wasted (unused) in the failing regions when an evacuation failure happens.
-  size_t failure_waste() const { return _failure_waste; }
+  size_t failure_waste() const;
 
   inline void add_num_plab_filled(size_t value);
   inline void add_direct_allocated(size_t value);

src/hotspot/share/gc/g1/g1EvacStats.inline.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2026, 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
@@ -27,28 +27,54 @@
 
 #include "gc/g1/g1EvacStats.hpp"
 
-#include "runtime/atomicAccess.hpp"
+inline uint G1EvacStats::regions_filled() const {
+  return _regions_filled.load_relaxed();
+}
+
+inline size_t G1EvacStats::num_plab_filled() const {
+  return _num_plab_filled.load_relaxed();
+}
+
+inline size_t G1EvacStats::region_end_waste() const {
+  return _region_end_waste.load_relaxed();
+}
+
+inline size_t G1EvacStats::direct_allocated() const {
+  return _direct_allocated.load_relaxed();
+}
+
+inline size_t G1EvacStats::num_direct_allocated() const {
+  return _num_direct_allocated.load_relaxed();
+}
+
+inline size_t G1EvacStats::failure_used() const {
+  return _failure_used.load_relaxed();
+}
+
+inline size_t G1EvacStats::failure_waste() const {
+  return _failure_waste.load_relaxed();
+}
 
 inline void G1EvacStats::add_direct_allocated(size_t value) {
-  AtomicAccess::add(&_direct_allocated, value, memory_order_relaxed);
+  _direct_allocated.add_then_fetch(value, memory_order_relaxed);
 }
 
 inline void G1EvacStats::add_num_plab_filled(size_t value) {
-  AtomicAccess::add(&_num_plab_filled, value, memory_order_relaxed);
+  _num_plab_filled.add_then_fetch(value, memory_order_relaxed);
 }
 
 inline void G1EvacStats::add_num_direct_allocated(size_t value) {
-  AtomicAccess::add(&_num_direct_allocated, value, memory_order_relaxed);
+  _num_direct_allocated.add_then_fetch(value, memory_order_relaxed);
 }
 
 inline void G1EvacStats::add_region_end_waste(size_t value) {
-  AtomicAccess::add(&_region_end_waste, value, memory_order_relaxed);
-  AtomicAccess::inc(&_regions_filled, memory_order_relaxed);
+  _region_end_waste.add_then_fetch(value, memory_order_relaxed);
+  _regions_filled.add_then_fetch(1u, memory_order_relaxed);
 }
 
 inline void G1EvacStats::add_failure_used_and_waste(size_t used, size_t waste) {
-  AtomicAccess::add(&_failure_used, used, memory_order_relaxed);
-  AtomicAccess::add(&_failure_waste, waste, memory_order_relaxed);
+  _failure_used.add_then_fetch(used, memory_order_relaxed);
+  _failure_waste.add_then_fetch(waste, memory_order_relaxed);
 }
 
 #endif // SHARE_GC_G1_G1EVACSTATS_INLINE_HPP