--- old/src/hotspot/share/gc/z/zObjectAllocator.cpp	2019-11-19 19:37:22.792833176 +0100
+++ new/src/hotspot/share/gc/z/zObjectAllocator.cpp	2019-11-19 19:37:22.317817535 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2019, 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
@@ -25,6 +25,7 @@
 #include "gc/z/zCollectedHeap.hpp"
 #include "gc/z/zGlobals.hpp"
 #include "gc/z/zHeap.inline.hpp"
+#include "gc/z/zHeuristics.hpp"
 #include "gc/z/zObjectAllocator.hpp"
 #include "gc/z/zPage.inline.hpp"
 #include "gc/z/zStat.hpp"
@@ -43,12 +44,21 @@
 static const ZStatCounter ZCounterUndoObjectAllocationFailed("Memory", "Undo Object Allocation Failed", ZStatUnitOpsPerSecond);
 
 ZObjectAllocator::ZObjectAllocator() :
+    _per_cpu_shared_small_page(ZHeuristics::per_cpu_shared_small_page()),
     _used(0),
     _undone(0),
     _shared_medium_page(NULL),
     _shared_small_page(NULL),
     _worker_small_page(NULL) {}
 
+ZPage** ZObjectAllocator::shared_small_page_addr() {
+  return _per_cpu_shared_small_page ? _shared_small_page.addr() : _shared_small_page.addr(0);
+}
+
+ZPage* const* ZObjectAllocator::shared_small_page_addr() const {
+  return _per_cpu_shared_small_page ? _shared_small_page.addr() : _shared_small_page.addr(0);
+}
+
 ZPage* ZObjectAllocator::alloc_page(uint8_t type, size_t size, ZAllocationFlags flags) {
   ZPage* const page = ZHeap::heap()->alloc_page(type, size, flags);
   if (page != NULL) {
@@ -72,7 +82,7 @@
                                                         size_t size,
                                                         ZAllocationFlags flags) {
   uintptr_t addr = 0;
-  ZPage* page = *shared_page;
+  ZPage* page = OrderAccess::load_acquire(shared_page);
 
   if (page != NULL) {
     addr = page->alloc_object_atomic(size);
@@ -142,7 +152,7 @@
   // Non-worker small page allocation can never use the reserve
   flags.set_no_reserve();
 
-  return alloc_object_in_shared_page(_shared_small_page.addr(), ZPageTypeSmall, ZPageSizeSmall, size, flags);
+  return alloc_object_in_shared_page(shared_small_page_addr(), ZPageTypeSmall, ZPageSizeSmall, size, flags);
 }
 
 uintptr_t ZObjectAllocator::alloc_small_object_from_worker(size_t size, ZAllocationFlags flags) {
@@ -294,7 +304,7 @@
 size_t ZObjectAllocator::remaining() const {
   assert(ZThread::is_java(), "Should be a Java thread");
 
-  ZPage* page = _shared_small_page.get();
+  const ZPage* const page = OrderAccess::load_acquire(shared_small_page_addr());
   if (page != NULL) {
     return page->remaining();
   }