Deprecate setting processors to more than available #44889
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Today the processors setting is permitted to be set to more than the number of processors available to the JVM. The processors setting directly sizes the number of threads in the various pool, with most of these sizes being a linear function in the number of processors. It doesn't make any sense to set processors more than the number of available processors, as there will not be any physical CPU resources on which to schedule the additional threads. This commit deprecates setting processors to more than the number of available processors.
jasontedor
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:Core/Infra/Core
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Pinging @elastic/es-core-infra |
jasontedor
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Jul 26, 2019
test/framework/src/main/java/org/elasticsearch/test/InternalTestCluster.java
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This change will be followed up with another to make the breaking change in master. |
jpountz
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Jul 26, 2019
Of course it's possible although I am not aware of an instance of this happening (only the JVM over-stating the number of available processors in some cases, for example, in response to |
jasontedor
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Jul 26, 2019
Today the processors setting is permitted to be set to more than the number of processors available to the JVM. The processors setting directly sizes the number of threads in the various thread pools, with most of these sizes being a linear function in the number of processors. It doesn't make any sense to set processors very high as the overhead from context switching amongst all the threads will overwhelm, and changing the setting does not control how many physical CPU resources there are on which to schedule the additional threads. We have to draw a line somewhere and this commit deprecates setting processors to more than the number of available processors. This is the right place to draw the line given the linear growth as a function of processors in most of the thread pools, and that some are capped at the number of available processors already.
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jkakavas
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Jul 31, 2019
Today the processors setting is permitted to be set to more than the number of processors available to the JVM. The processors setting directly sizes the number of threads in the various thread pools, with most of these sizes being a linear function in the number of processors. It doesn't make any sense to set processors very high as the overhead from context switching amongst all the threads will overwhelm, and changing the setting does not control how many physical CPU resources there are on which to schedule the additional threads. We have to draw a line somewhere and this commit deprecates setting processors to more than the number of available processors. This is the right place to draw the line given the linear growth as a function of processors in most of the thread pools, and that some are capped at the number of available processors already.
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What will happen if I start node in k8s with limit set. Will it adjust according to limit or according to CPU on node? |
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Today the processors setting is permitted to be set to more than the number of processors available to the JVM. The processors setting directly sizes the number of threads in the various thread pools, with most of these sizes being a linear function in the number of processors. It doesn't make any sense to set processors very high as the overhead from context switching amongst all the threads will overwhelm, and changing the setting does not control how many physical CPU resources there are on which to schedule the additional threads. We have to draw a line somewhere and this commit deprecates setting processors to more than the number of available processors. This is the right place to draw the line given the linear growth as a function of processors in most of the thread pools, and that some are capped at the number of available processors already.