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From "Tianyin Xu (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (YARN-4499) Bad config values of "yarn.scheduler.maximum-allocation-vcores"
Date Wed, 23 Dec 2015 08:02:46 GMT

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

Tianyin Xu updated YARN-4499:
-----------------------------
    Summary: Bad config values of "yarn.scheduler.maximum-allocation-vcores"  (was: Bad config
values of "scheduler.maximum-allocation-vcores")

> 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 {{4}},
according to {{YarnConfiguration.java}}
> {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}
> However, according to [yarn-default.xml|https://hadoop.apache.org/docs/r2.7.1/hadoop-yarn/hadoop-yarn-common/yarn-default.xml],
this value should be {{32}}.
> Yes, this seems to be a doc error, but 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 (of {{yarn.nodemanager.resource.cpu-vcores}}) is usually
equal to {{yarn.nodemanager.resource.cpu-vcores}}..."
> At least, we should fix the doc. 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 default which is equal to the number
of cores on the machine...)



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