Update the default value for number of UDP listeners (#40761)

CHANGES

@@ -1,3 +1,6 @@
+4236.	[func]		Set the default value for the number of UDP listeners
+			to the number of detected processors (CPU). [RT #40761]
+
 4235.	[func]		Added support in named for "dnstap", a fast method of
 			capturing and logging DNS traffic, and a new command
 			"dnstap-read" to read a dnstap log file.  Use

bin/named/main.c

@@ -724,6 +724,8 @@ create_managers(void) {
 	isc_result_t result;
 	unsigned int socks;
 
+	INSIST(ns_g_cpus_detected > 0);
+
 #ifdef ISC_PLATFORM_USETHREADS
 	if (ns_g_cpus == 0)
 		ns_g_cpus = ns_g_cpus_detected;
@@ -740,10 +742,8 @@ create_managers(void) {
 	if (ns_g_udpdisp == 0) {
 		if (ns_g_cpus_detected == 1)
 			ns_g_udpdisp = 1;
-		else if (ns_g_cpus_detected < 4)
-			ns_g_udpdisp = 2;
 		else
-			ns_g_udpdisp = ns_g_cpus_detected / 2;
+			ns_g_udpdisp = ns_g_cpus_detected - 1;
 	}
 	if (ns_g_udpdisp > ns_g_cpus)
 		ns_g_udpdisp = ns_g_cpus;

doc/arm/notes.xml

@@ -663,6 +663,12 @@
 	   transport the query was received over.
 	</para>
       </listitem>
+      <listitem>
+	<para>
+	  The default value for the number of UDP listeners has been
+	  changed to the number of detected processors (CPU).
+	</para>
+      </listitem>
     </itemizedlist>
   </sect2>
   <sect2 id="relnotes_port">