[jira] [Updated] (TEZ-3126) Log reason for not reducing parallelism

["Jonathan Eagles (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/TEZ-3126?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jonathan Eagles updated TEZ-3126:
---------------------------------
    Summary: Log reason for not reducing parallelism  (was: Auto-Reduce Parallelism: Vertex not re-configured when reduced by less than half.)

> Log reason for not reducing parallelism
> ---------------------------------------
>
>                 Key: TEZ-3126
>                 URL: https://issues.apache.org/jira/browse/TEZ-3126
>             Project: Apache Tez
>          Issue Type: Bug
>            Reporter: Jonathan Eagles
>            Assignee: Jonathan Eagles
>            Priority: Critical
>         Attachments: TEZ-3126.1.patch
>
>
> For example, when reducing parallelism from 36 to 22. The basePartitionRange will be 1 and will not re-configure the vertex.
> {code:java|title=ShuffleVertexManager#determineParallelismAndApply|borderStyle=dashed|bgColor=lightgrey}
>     int desiredTaskParallelism = 
>         (int)(
>             (expectedTotalSourceTasksOutputSize+desiredTaskInputDataSize-1)/
>             desiredTaskInputDataSize);
>     if(desiredTaskParallelism < minTaskParallelism) {
>       desiredTaskParallelism = minTaskParallelism;
>     }
>     
>     if(desiredTaskParallelism >= currentParallelism) {
>       return true;
>     }
>     
>     // most shufflers will be assigned this range
>     basePartitionRange = currentParallelism/desiredTaskParallelism;
>     
>     if (basePartitionRange <= 1) {
>       // nothing to do if range is equal 1 partition. shuffler does it by default
>       return true;
>     }
> {code}



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