Add more documentation about shared memory costs.

tglsfdc · tglsfdc · commit 3df163ad8985 · 2003-04-19T00:37:28.000Z
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
@@ -47,12 +47,15 @@
 #
 #	Shared Memory Size
 #
-#shared_buffers = 64		# min max_connections*2 or 16, 8KB each
-#max_locks_per_transaction = 64	# min 10
-#wal_buffers = 8		# min 4, typically 8KB each
+#shared_buffers = 64		# min 16, at least max_connections*2, 8KB each
+#max_locks_per_transaction = 64	# min 10, ~260*max_connections bytes each
+#wal_buffers = 8		# min 4, 8KB each
 # fsm = free space map
 #max_fsm_relations = 1000	# min 100, ~50 bytes each
 #max_fsm_pages = 20000		# min max_fsm_relations*16, 6 bytes each
+# note: increasing max_connections also costs about 500 bytes each,
+# in addition to costs from shared_buffers and max_locks_per_transaction.
+
 
 #
 #	Non-shared Memory Sizes

Original file line number	Diff line number	Diff line change
`@@ -47,12 +47,15 @@`
`47`	`47`	`#`
`48`	`48`	`# Shared Memory Size`
`49`	`49`	`#`
`50`		`-#shared_buffers = 64 # min max_connections*2 or 16, 8KB each`
`51`		`-#max_locks_per_transaction = 64 # min 10`
`52`		`-#wal_buffers = 8 # min 4, typically 8KB each`
	`50`	`+#shared_buffers = 64 # min 16, at least max_connections*2, 8KB each`
	`51`	`+#max_locks_per_transaction = 64 # min 10, ~260*max_connections bytes each`
	`52`	`+#wal_buffers = 8 # min 4, 8KB each`
`53`	`53`	`# fsm = free space map`
`54`	`54`	`#max_fsm_relations = 1000 # min 100, ~50 bytes each`
`55`	`55`	`#max_fsm_pages = 20000 # min max_fsm_relations*16, 6 bytes each`
	`56`	`+# note: increasing max_connections also costs about 500 bytes each,`
	`57`	`+# in addition to costs from shared_buffers and max_locks_per_transaction.`
	`58`	`+`
`56`	`59`
`57`	`60`	`#`
`58`	`61`	`# Non-shared Memory Sizes`