Re: [PATCH] BUG #13416: Postgres >= 9.3 doesn't use optimized shared memory on Solaris anymore

diff --git c/src/backend/port/sysv_shmem.c w/src/backend/port/sysv_shmem.c
index 850eafddc3..bbc3cbbd2a 100644
--- c/src/backend/port/sysv_shmem.c
+++ w/src/backend/port/sysv_shmem.c
@@ -55,15 +55,20 @@
  * false, we might need to add compile and/or run-time tests here and do this
  * only if the running kernel supports it.
  *
- * However, we must always disable this logic in the EXEC_BACKEND case, and
+ * There are two cases in which we disable this logic. On systems that support
+ * intimate shared memory (e.g. illumos and Solaris), we prefer the usage of
+ * System V shared memory in order to take advantage of the performance
+ * improvements that sharing page tables provides.
+ *
+ * In addition, we must always disable this logic in the EXEC_BACKEND case, and
  * fall back to the old method of allocating the entire segment using System V
  * shared memory, because there's no way to attach an anonymous mmap'd segment
  * to a process after exec().  Since EXEC_BACKEND is intended only for
  * developer use, this shouldn't be a big problem.  Because of this, we do
  * not worry about supporting anonymous shmem in the EXEC_BACKEND cases below.
  */
-#ifndef EXEC_BACKEND
-#define USE_ANONYMOUS_SHMEM
+#if !defined(EXEC_BACKEND) && !defined(SHMEM_TYPE_SYSV)
+#  define USE_ANONYMOUS_SHMEM
 #endif
 
 
@@ -576,17 +581,23 @@ PGSharedMemoryCreate(Size size, bool makePrivate, int port,
 	Assert(size > MAXALIGN(sizeof(PGShmemHeader)));
 
 #ifdef USE_ANONYMOUS_SHMEM
-	AnonymousShmem = CreateAnonymousSegment(&size);
-	AnonymousShmemSize = size;
+	if (shared_memory_type == SHMEM_TYPE_MMAP)
+	{
+		AnonymousShmem = CreateAnonymousSegment(&size);
+		AnonymousShmemSize = size;
 
-	/* Register on-exit routine to unmap the anonymous segment */
-	on_shmem_exit(AnonymousShmemDetach, (Datum) 0);
+		/* Register on-exit routine to unmap the anonymous segment */
+		on_shmem_exit(AnonymousShmemDetach, (Datum) 0);
 
-	/* Now we need only allocate a minimal-sized SysV shmem block. */
-	sysvsize = sizeof(PGShmemHeader);
-#else
-	sysvsize = size;
+		/* Now we need only allocate a minimal-sized SysV shmem block. */
+		sysvsize = sizeof(PGShmemHeader);
+	}
+	else
 #endif
+	{
+		Assert(shared_memory_type == SHMEM_TYPE_SYSV);
+		sysvsize = size;
+	}
 
 	/* Make sure PGSharedMemoryAttach doesn't fail without need */
 	UsedShmemSegAddr = NULL;
diff --git c/src/backend/storage/ipc/ipci.c w/src/backend/storage/ipc/ipci.c
index c04b17fa8e..44c3a28aa2 100644
--- c/src/backend/storage/ipc/ipci.c
+++ w/src/backend/storage/ipc/ipci.c
@@ -45,6 +45,8 @@
 #include "storage/spin.h"
 #include "utils/snapmgr.h"
 
+/* GUCs */
+int	shared_memory_type = DEFAULT_SHARED_MEMORY_TYPE;
 
 shmem_startup_hook_type shmem_startup_hook = NULL;
 
diff --git c/src/backend/utils/misc/guc.c w/src/backend/utils/misc/guc.c
index 4f1891f844..9527cc028a 100644
--- c/src/backend/utils/misc/guc.c
+++ w/src/backend/utils/misc/guc.c
@@ -393,6 +393,19 @@ static const struct config_enum_entry force_parallel_mode_options[] = {
 	{NULL, 0, false}
 };
 
+static struct config_enum_entry shared_memory_options[] = {
+#ifndef WIN32
+	{ "sysv", SHMEM_TYPE_SYSV, false},
+#endif
+#ifndef EXEC_BACKEND
+	{ "mmap", SHMEM_TYPE_MMAP, false},
+#endif
+#ifdef WIN32
+	{ "windows", SHMEM_TYPE_WINDOWS, false},
+#endif
+	{NULL, 0, false}
+};
+
 /*
  * Options for enum values stored in other modules
  */
@@ -3748,6 +3761,16 @@ static struct config_enum ConfigureNamesEnum[] =
 	},
 
 	{
+		{"shared_memory_type", PGC_POSTMASTER, RESOURCES_MEM,
+			gettext_noop("Selects the shared memory implementation used."),
+			NULL
+		},
+		&shared_memory_type,
+		DEFAULT_SHARED_MEMORY_TYPE, shared_memory_options,
+		NULL, NULL, NULL
+	},
+
+	{
 		{"dynamic_shared_memory_type", PGC_POSTMASTER, RESOURCES_MEM,
 			gettext_noop("Selects the dynamic shared memory implementation used."),
 			NULL
diff --git c/src/backend/utils/misc/postgresql.conf.sample w/src/backend/utils/misc/postgresql.conf.sample
index fa6c0eaa80..8f59028ea2 100644
--- c/src/backend/utils/misc/postgresql.conf.sample
+++ w/src/backend/utils/misc/postgresql.conf.sample
@@ -124,6 +124,11 @@
 #replacement_sort_tuples = 150000	# limits use of replacement selection sort
 #autovacuum_work_mem = -1		# min 1MB, or -1 to use maintenance_work_mem
 #max_stack_depth = 2MB			# min 100kB
+#shared_memory_type = mmap		# the default is the first option
+					# supported by the operating system:
+					#   mmap
+					#   sysv
+					#   windows
 #dynamic_shared_memory_type = posix	# the default is the first option
 					# supported by the operating system:
 					#   posix
diff --git c/src/bin/initdb/initdb.c w/src/bin/initdb/initdb.c
index 27d134e17d..329ed88c8b 100644
--- c/src/bin/initdb/initdb.c
+++ w/src/bin/initdb/initdb.c
@@ -1050,12 +1050,13 @@ set_null_conf(void)
  * attempt to reproduce what the postmaster will do when allocating a POSIX
  * segment in dsm_impl.c; if it doesn't work, we assume it won't work for
  * the postmaster either, and configure the cluster for System V shared
- * memory instead.
+ * memory instead. However, on Solaris-derived systems, System V shared
+ * memory is preferred.
  */
 static char *
 choose_dsm_implementation(void)
 {
-#ifdef HAVE_SHM_OPEN
+#if defined(HAVE_SHM_OPEN) && !defined(__sun)
 	int			ntries = 10;
 
 	while (ntries > 0)
diff --git c/src/include/storage/pg_shmem.h w/src/include/storage/pg_shmem.h
index 6bf803ab88..761fd48df0 100644
--- c/src/include/storage/pg_shmem.h
+++ w/src/include/storage/pg_shmem.h
@@ -41,9 +41,18 @@ typedef struct PGShmemHeader	/* standard header for all Postgres shmem */
 #endif
 } PGShmemHeader;
 
-/* GUC variable */
+/* GUC variables */
+extern int	shared_memory_type;
 extern int	huge_pages;
 
+/* Possible values for shared_memory_type */
+typedef enum
+{
+	SHMEM_TYPE_WINDOWS,
+	SHMEM_TYPE_SYSV,
+	SHMEM_TYPE_MMAP
+}	PGShmemType;
+
 /* Possible values for huge_pages */
 typedef enum
 {
@@ -59,6 +68,14 @@ extern HANDLE UsedShmemSegID;
 #endif
 extern void *UsedShmemSegAddr;
 
+#if !defined(WIN32) && !defined(EXEC_BACKEND)
+#define DEFAULT_SHARED_MEMORY_TYPE SHMEM_TYPE_MMAP
+#elif !defined(WIN32)
+#define DEFAULT_SHARED_MEMORY_TYPE SHMEM_TYPE_SYSV
+#else
+#define DEFAULT_SHARED_MEMORY_TYPE SHMEM_TYPE_WINDOWS
+#endif
+
 #ifdef EXEC_BACKEND
 extern void PGSharedMemoryReAttach(void);
 extern void PGSharedMemoryNoReAttach(void);