sysv_shmem.patch

--- src/backend/port/sysv_shmem.c.orig	2013-11-19 16:45:58.825487864 +0400
+++ src/backend/port/sysv_shmem.c	2013-11-19 16:45:44.485488312 +0400
@@ -61,6 +61,8 @@
 #define MAP_FAILED ((void *) -1)
 #endif
 
+#define LINUX_SHMEM_LIMIT (256LL*1024*1024*1024)
+
 
 unsigned long UsedShmemSegID = 0;
 void	   *UsedShmemSegAddr = NULL;
@@ -369,10 +371,17 @@
 	IpcMemoryId shmid;
 	struct stat statbuf;
 	Size		sysvsize = size;
+    int         mmapFlags = PG_MMAP_FLAGS;
 
 	/* Room for a header? */
 	Assert(size > MAXALIGN(sizeof(PGShmemHeader)));
 
+#ifdef MAP_HUGETLB
+    if (size > LINUX_SHMEM_LIMIT) { 
+        mmapFlags |= MAP_HUGETLB;
+    }
+#endif
+
 	/*
 	 * As of PostgreSQL 9.3, we normally allocate only a very small amount of
 	 * System V shared memory, and only for the purposes of providing an
@@ -410,8 +419,7 @@
 		 * out to be false, we might need to add a run-time test here and do
 		 * this only if the running kernel supports it.
 		 */
-		AnonymousShmem = mmap(NULL, size, PROT_READ | PROT_WRITE, PG_MMAP_FLAGS,
-							  -1, 0);
+		AnonymousShmem = mmap(NULL, size, PROT_READ | PROT_WRITE, mmapFlags, -1, 0);
 		if (AnonymousShmem == MAP_FAILED)
 			ereport(FATAL,
 					(errmsg("could not map anonymous shared memory: %m"),