config: Split "Worker Processes" out of "Asynchronous Behavior"

Having all the worker related GUCs in the same section as IO controlling GUCs
doesn't really make sense. Create a separate section for them.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/x3tlw2jk5gm3r3mv47hwrshffyw7halpczkfbk3peksxds7bvc@lguk43z3bsyq

doc/src/sgml/config.sgml

@@ -2618,7 +2618,13 @@ include_dir 'conf.d'
         </para>
        </listitem>
       </varlistentry>
+     </variablelist>
+    </sect2>
 
+    <sect2 id="runtime-config-resource-worker-processes">
+     <title>Worker Processes</title>
+
+     <variablelist>
       <varlistentry id="guc-max-worker-processes" xreflabel="max_worker_processes">
        <term><varname>max_worker_processes</varname> (<type>integer</type>)
        <indexterm>

src/backend/utils/misc/guc_tables.c

@@ -683,6 +683,7 @@ const char *const config_group_names[] =
 	[RESOURCES_KERNEL] = gettext_noop("Resource Usage / Kernel Resources"),
 	[RESOURCES_BGWRITER] = gettext_noop("Resource Usage / Background Writer"),
 	[RESOURCES_ASYNCHRONOUS] = gettext_noop("Resource Usage / Asynchronous Behavior"),
+	[RESOURCES_WORKER_PROCESSES] = gettext_noop("Resource Usage / Worker Processes"),
 	[WAL_SETTINGS] = gettext_noop("Write-Ahead Log / Settings"),
 	[WAL_CHECKPOINTS] = gettext_noop("Write-Ahead Log / Checkpoints"),
 	[WAL_ARCHIVING] = gettext_noop("Write-Ahead Log / Archiving"),
@@ -1962,7 +1963,7 @@ struct config_bool ConfigureNamesBool[] =
 	},
 
 	{
-		{"parallel_leader_participation", PGC_USERSET, RESOURCES_ASYNCHRONOUS,
+		{"parallel_leader_participation", PGC_USERSET, RESOURCES_WORKER_PROCESSES,
 			gettext_noop("Controls whether Gather and Gather Merge also run subplans."),
 			gettext_noop("Should gather nodes also run subplans or just gather tuples?"),
 			GUC_EXPLAIN
@@ -3234,7 +3235,7 @@ struct config_int ConfigureNamesInt[] =
 	{
 		{"max_worker_processes",
 			PGC_POSTMASTER,
-			RESOURCES_ASYNCHRONOUS,
+			RESOURCES_WORKER_PROCESSES,
 			gettext_noop("Maximum number of concurrent worker processes."),
 			NULL,
 		},
@@ -3496,7 +3497,7 @@ struct config_int ConfigureNamesInt[] =
 	},
 
 	{
-		{"max_parallel_maintenance_workers", PGC_USERSET, RESOURCES_ASYNCHRONOUS,
+		{"max_parallel_maintenance_workers", PGC_USERSET, RESOURCES_WORKER_PROCESSES,
 			gettext_noop("Sets the maximum number of parallel processes per maintenance operation."),
 			NULL
 		},
@@ -3506,7 +3507,7 @@ struct config_int ConfigureNamesInt[] =
 	},
 
 	{
-		{"max_parallel_workers_per_gather", PGC_USERSET, RESOURCES_ASYNCHRONOUS,
+		{"max_parallel_workers_per_gather", PGC_USERSET, RESOURCES_WORKER_PROCESSES,
 			gettext_noop("Sets the maximum number of parallel processes per executor node."),
 			NULL,
 			GUC_EXPLAIN
@@ -3517,7 +3518,7 @@ struct config_int ConfigureNamesInt[] =
 	},
 
 	{
-		{"max_parallel_workers", PGC_USERSET, RESOURCES_ASYNCHRONOUS,
+		{"max_parallel_workers", PGC_USERSET, RESOURCES_WORKER_PROCESSES,
 			gettext_noop("Sets the maximum number of parallel workers that can be active at one time."),
 			NULL,
 			GUC_EXPLAIN

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

@@ -198,6 +198,9 @@
 #effective_io_concurrency = 1		# 1-1000; 0 disables prefetching
 #maintenance_io_concurrency = 10	# 1-1000; 0 disables prefetching
 #io_combine_limit = 128kB		# usually 1-32 blocks (depends on OS)
+
+# - Worker Processes -
+
 #max_worker_processes = 8		# (change requires restart)
 #max_parallel_workers_per_gather = 2	# limited by max_parallel_workers
 #max_parallel_maintenance_workers = 2	# limited by max_parallel_workers

src/include/utils/guc_tables.h

@@ -65,6 +65,7 @@ enum config_group
 	RESOURCES_KERNEL,
 	RESOURCES_BGWRITER,
 	RESOURCES_ASYNCHRONOUS,
+	RESOURCES_WORKER_PROCESSES,
 	WAL_SETTINGS,
 	WAL_CHECKPOINTS,
 	WAL_ARCHIVING,