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https://issues.apache.org/jira/browse/SPARK-19244?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Mridul Muralidharan reassigned SPARK-19244:
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    Assignee: Liang-Chi Hsieh

> Sort MemoryConsumers according to their memory usage when spilling
> ------------------------------------------------------------------
>
>                 Key: SPARK-19244
>                 URL: https://issues.apache.org/jira/browse/SPARK-19244
>             Project: Spark
>          Issue Type: Improvement
>          Components: Spark Core
>            Reporter: Liang-Chi Hsieh
>            Assignee: Liang-Chi Hsieh
>             Fix For: 2.2.0
>
>
> In `TaskMemoryManager `, when we acquire memory by calling 
> `acquireExecutionMemory` and we can't acquire required memory, we will try to 
> spill other memory consumers.
> Currently, we simply iterates the memory consumers in a hash set. Normally 
> each time the consumer will be iterated in the same order.
> The first issue is that we might spill additional consumers. For example, if 
> consumer 1 uses 10MB, consumer 2 uses 50MB, then consumer 3 acquires 100MB 
> but we can only get 60MB and spilling is needed. We might spill both consumer 
> 1 and consumer 2. But we actually just need to spill consumer 2 and get the 
> required 100MB.
> The second issue is that if we spill consumer 1 in first time spilling. After 
> a while, consumer 1 now uses 5MB. Then consumer 4 may acquire some memory and 
> spilling is needed again. Because we iterate the memory consumers in the same 
> order, we will spill consumer 1 again. So for consumer 1, we will produce 
> many small spilling files.



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