[jira] [Resolved] (YARN-4499) Bad config values of "yarn.scheduler.maximum-allocation-vcores"

["Tianyin Xu (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/YARN-4499?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Tianyin Xu resolved YARN-4499.
------------------------------
    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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