Use more RMQ flags for less busy wait

As mentioned in the Iced014acee7e590c10848e73feca166f48b622dc
commit message, in Ussuri+ we can use ``+sbwtdcpu none
+sbwtdio none`` as well. This is due to relying on RMQ-provided
erlang in version 23.x.

This change adds the extra arguments by default.
It should be backported down to Ussuri before we do a release with
Iced014acee7e590c10848e73feca166f48b622dc.

Change-Id: I32e247a6cb34d7f6763b544f247fd408dce2b3a2

ansible/roles/rabbitmq/defaults/main.yml

@@ -85,7 +85,7 @@ rabbitmq_user: "openstack"
 rabbitmq_cluster_name: "openstack"
 rabbitmq_hostname: "{{ ansible_facts.hostname }}"
 rabbitmq_pid_file: "/var/lib/rabbitmq/mnesia/rabbitmq.pid"
-rabbitmq_server_additional_erl_args: "+S 2:2 +sbwt none"
+rabbitmq_server_additional_erl_args: "+S 2:2 +sbwt none +sbwtdcpu none +sbwtdio none"
 # Dict of TLS options for RabbitMQ. Keys will be prefixed with 'ssl_options.'.
 rabbitmq_tls_options: {}
 # To avoid split-brain

doc/source/reference/message-queues/rabbitmq.rst

@@ -97,7 +97,7 @@ already configures RabbitMQ server for IPv6 (if necessary). Any argument can be
 passed there as documented in https://www.rabbitmq.com/runtime.html
 
 The default value for ``rabbitmq_server_additional_erl_args`` is ``+S 2:2 +sbwt
-none``.
+none +sbwtdcpu none +sbwtdio none``.
 
 By default RabbitMQ starts N schedulers where N is the number of CPU cores,
 including hyper-threaded cores. This is fine when you assume all CPUs are
@@ -106,5 +106,6 @@ Here we go for two scheduler threads (``+S 2:2``).  More details can be found
 here: https://www.rabbitmq.com/runtime.html#scheduling and here:
 https://erlang.org/doc/man/erl.html#emulator-flags
 
-The ``+sbwt`` argument prevents busy waiting of the scheduler, for more details
-see: https://www.rabbitmq.com/runtime.html#busy-waiting.
+The ``+sbwt none +sbwtdcpu none +sbwtdio none`` arguments prevent busy waiting
+of the scheduler, for more details see:
+https://www.rabbitmq.com/runtime.html#busy-waiting.

etc/kolla/globals.yml

@@ -417,8 +417,8 @@
 # https://www.rabbitmq.com/runtime.html#scheduling
 # https://www.rabbitmq.com/runtime.html#busy-waiting
 # The default tells RabbitMQ to always use two cores (+S 2:2),
-# and not to busy wait (+sbwt none):
-#rabbitmq_server_additional_erl_args: "+S 2:2 +sbwt none"
+# and not to busy wait (+sbwt none +sbwtdcpu none +sbwtdio none):
+#rabbitmq_server_additional_erl_args: "+S 2:2 +sbwt none +sbwtdcpu none +sbwtdio none"
 # Whether to enable TLS encryption for RabbitMQ client-server communication.
 #rabbitmq_enable_tls: "no"
 # CA certificate bundle in RabbitMQ container.

releasenotes/notes/reduce-rabbit-busy-waiting-085433c822165eab.yaml

@@ -10,4 +10,4 @@ fixes:
 upgrade:
   - |
     Modifies the default value of ``rabbitmq_server_additional_erl_args`` from
-    an empty string to ``+S 2:2 +sbwt none``.
+    an empty string to ``+S 2:2 +sbwt none +sbwtdcpu none +sbwtdio none``.