--- a/src/hotspot/share/gc/z/zObjectAllocator.hpp	Tue Aug 06 15:49:53 2019 +0200
+++ b/src/hotspot/share/gc/z/zObjectAllocator.hpp	Tue Aug 06 15:50:00 2019 +0200
@@ -33,11 +33,13 @@
 private:
   const uint         _nworkers;
   ZPerCPU<size_t>    _used;
+  ZPerCPU<size_t>    _undone;
   ZContended<ZPage*> _shared_medium_page;
   ZPerCPU<ZPage*>    _shared_small_page;
   ZPerWorker<ZPage*> _worker_small_page;
 
   ZPage* alloc_page(uint8_t type, size_t size, ZAllocationFlags flags);
+  void undo_alloc_page(ZPage* page);
 
   // Allocate an object in a shared page. Allocate and
   // atomically install a new page if necessary.