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https://issues.apache.org/jira/browse/YARN-4499?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tianyin Xu resolved YARN-4499.
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Resolution: Duplicate
> Bad config values of "yarn.scheduler.maximum-allocation-vcores"
> ---------------------------------------------------------------
>
> Key: YARN-4499
> URL: https://issues.apache.org/jira/browse/YARN-4499
> Project: Hadoop YARN
> Issue Type: Bug
> Components: scheduler
> Affects Versions: 2.7.1, 2.6.2
> Reporter: Tianyin Xu
>
> Currently, the default value of {{yarn.scheduler.maximum-allocation-vcores}}
> is {{32}}, according to
> [yarn-default.xml|https://hadoop.apache.org/docs/r2.7.1/hadoop-yarn/hadoop-yarn-common/yarn-default.xml].
> However, in {{YarnConfiguration.java}}, we specify the default to be {{4}}.
> {code}
> public static final String RM_SCHEDULER_MAXIMUM_ALLOCATION_VCORES =
> YARN_PREFIX + "scheduler.maximum-allocation-vcores";
> public static final int DEFAULT_RM_SCHEDULER_MAXIMUM_ALLOCATION_VCORES = 4;
> {code}
> The default in the code looks correct to me. Actually I feel that the default
> value should be the same as {{yarn.nodemanager.resource.cpu-vcores}} (whose
> default is {{8}}) ---if we have {{8}} cores for scheduling, there's few
> reason we only allow the maximum of {{4}}...
> The Cloudera's article on [Tuning the Cluster for MapReduce v2 (YARN)
> |http://www.cloudera.com/content/www/en-us/documentation/enterprise/5-3-x/topics/cdh_ig_yarn_tuning.html]
> also suggests that "the maximum value (
> {{yarn.scheduler.maximum-allocation-vcores}}) is usually equal to
> {{yarn.nodemanager.resource.cpu-vcores}}..."
> At the very least, we should fix
> [yarn-default.xml|https://hadoop.apache.org/docs/r2.7.1/hadoop-yarn/hadoop-yarn-common/yarn-default.xml].
> The error is pretty bad. A simple search on the Internet shows some ppl are
> confused by this error, for example,
> https://community.cloudera.com/t5/Cloudera-Manager-Installation/yarn-nodemanager-resource-cpu-vcores-and-yarn-scheduler-maximum/td-p/31098
> \\
> (but seriously, I think we should have an automatic defaults with the min as
> 1 and the max equal to the number of cores on the machine...
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