Improve postgresql.conf descriptions.

src/backend/utils/misc/postgresql.conf.sample

@@ -45,30 +45,30 @@
 #	Shared Memory Size
 #
 #shared_buffers = 64        # 2*max_connections, min 16
-#max_fsm_relations = 100    # min 10
-#max_fsm_pages = 10000      # min 1000
+#max_fsm_relations = 100    # min 10, fsm is free space map
+#max_fsm_pages = 10000      # min 1000, fsm is free space map
 #max_locks_per_transaction = 64 # min 10
 #wal_buffers = 8            # min 4
 
 #
-#	Performance
+#	Non-shared Memory Sizes
 #
 #sort_mem = 512             # min 32
 #vacuum_mem = 8192          # min 1024
-#fsync = true
 
 
 #
 #	Write-ahead log (WAL)
 #
 #wal_files = 0 # range 0-64
-#wal_sync_method = fsync   # fsync or fdatasync or open_sync or open_datasync
-# Note: default wal_sync_method varies across platforms
+#wal_sync_method = fsync   # the default varies across platforms:
+#			   # fsync, fdatasync, open_sync, or open_datasync
 #wal_debug = 0             # range 0-16
 #commit_delay = 0          # range 0-100000
 #commit_siblings = 5       # range 1-1000
 #checkpoint_segments = 3   # in logfile segments (16MB each), min 1
 #checkpoint_timeout = 300  # in seconds, range 30-3600
+#fsync = true
 
 
 #