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https://issues.apache.org/jira/browse/TEZ-2244?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14978808#comment-14978808
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Rajesh Balamohan commented on TEZ-2244:
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[~hitesh] - It depends on the sort buffers. So if > 2GB is set, it would try to
create multiple 2000MB chunks & in case lesser sort buffer is configured, it
would end up using a single block (within the limit specified in sort buffer
limit). This is to support the existing default model.
> PipelinedSorter: Progressive allocation for sort-buffers
> --------------------------------------------------------
>
> Key: TEZ-2244
> URL: https://issues.apache.org/jira/browse/TEZ-2244
> Project: Apache Tez
> Issue Type: Improvement
> Affects Versions: 0.7.0
> Reporter: Gopal V
> Assignee: Rajesh Balamohan
> Attachments: TEZ-2244.1.patch, TEZ-2244.2.patch, TEZ-2244.3.patch,
> TEZ-2244.4.patch, TEZ-2244.5.patch, TEZ-2244.6.patch, TEZ-2244.7.patch,
> TEZ-2244.WIP.patch
>
>
> Currently, the sort buffers are allocated pessimistically for all tasks so
> that the largest task's spill stays within memory.
> After the chained buffer implementation inside PipelinedSorter, it brings up
> the possibility of only allocating the first chunk of the sort buffer when
> the sorter starts up.
> This allows for the tasks which do not heavily use the sort buffer (like a
> grouping aggregation) to use the sort-space only when the map-aggregation
> turns itself off.
> Not reserving memory on startup hurts the worst-case scenario for the
> pipelined sorter, but improves the average case.
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