John Garbutt 70f6f8e4c0 Reduce RabbitMQ busy waiting, lowering CPU load ... On machines with many cores, we were seeing excessive CPU load on systems that were not very busy. With the following Erlang VM argument we saw RabbitMQ CPU usage drop from about 150% to around 20%, on a system with 40 hyperthreads. +S 2:2 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 your CPUs are dedicated to RabbitMQ. Its not a good idea in a typical Kolla Ansible setup. Here we go for two scheduler threads. More details can be found here: https://www.rabbitmq.com/runtime.html#scheduling and here: https://erlang.org/doc/man/erl.html#emulator-flags +sbwt none This stops busy waiting of the scheduler, for more details see: https://www.rabbitmq.com/runtime.html#busy-waiting Newer versions of rabbit may need additional flags: "+sbwt none +sbwtdcpu none +sbwtdio none" But this patch should be back portable to older versions of RabbitMQ used in Train and Stein. Note that information on this tuning was found by looking at data from: rabbitmq-diagnostics runtime_thread_stats More details on that can be found here: https://www.rabbitmq.com/runtime.html#thread-stats Related-Bug: #1846467 Change-Id: Iced014acee7e590c10848e73feca166f48b622dc		2021-06-07 13:18:39 +01:00
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index.rst	Allow passing arguments to RabbitMQ server	2019-10-25 11:38:45 +02:00
rabbitmq.rst	Reduce RabbitMQ busy waiting, lowering CPU load	2021-06-07 13:18:39 +01:00