From 370253f95a7910db0e2dd4b86d6240af688d6b46 Mon Sep 17 00:00:00 2001 From: Jason Tedor Date: Fri, 14 Oct 2016 05:48:41 -0400 Subject: [PATCH] Add doc note regarding processors bound This commit expands the thread pool docs regarding the processor setting. Relates #20895 --- docs/reference/modules/threadpool.asciidoc | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) diff --git a/docs/reference/modules/threadpool.asciidoc b/docs/reference/modules/threadpool.asciidoc index a333312e0fb..4e8b5c61efd 100644 --- a/docs/reference/modules/threadpool.asciidoc +++ b/docs/reference/modules/threadpool.asciidoc @@ -118,14 +118,30 @@ thread_pool: [[processors]] === Processors setting The number of processors is automatically detected, and the thread pool -settings are automatically set based on it. Sometimes, the number of processors -are wrongly detected, in such cases, the number of processors can be -explicitly set using the `processors` setting. +settings are automatically set based on it. In some cases it can be +useful to override the number of detected processors. This can be done +by explicitly setting the `processors` setting. [source,yaml] -------------------------------------------------- processors: 2 -------------------------------------------------- +There are a few use-cases for explicitly overriding the `processors` +setting: + +. If you are running multiple instances of Elasticsearch on the same +host but want Elasticsearch to size its thread pools as if it only has a +fraction of the CPU, you should override the `processors` setting to the +desired fraction (e.g., if you're running two instances of Elasticsearch +on a 16-core machine, set `processors` to 8). Note that this is an +expert-level use-case and there's a lot more involved than just setting +the `processors` setting as there are other considerations like changing +the number of garbage collector threads, pinning processes to cores, +etc. +. Sometimes the number of processors is wrongly detected and in such +cases explicitly setting the `processors` setting will workaround such +issues. + In order to check the number of processors detected, use the nodes info API with the `os` flag.