Index: contrib/jemalloc/include/jemalloc/internal/jemalloc_internal_defs.h
===================================================================
--- contrib/jemalloc/include/jemalloc/internal/jemalloc_internal_defs.h
+++ contrib/jemalloc/include/jemalloc/internal/jemalloc_internal_defs.h
@@ -215,7 +215,7 @@
  * common sequences of mmap()/munmap() calls will cause virtual memory map
  * holes.
  */
-/* #undef JEMALLOC_RETAIN */
+#define JEMALLOC_RETAIN
 
 /* TLS is used to map arenas and magazine caches to threads. */
 #define JEMALLOC_TLS