Siddharth Seth commented on TEZ-3430:

+1. Thanks [~mingma]

> Make split sorting optional
> ---------------------------
>                 Key: TEZ-3430
>                 URL: https://issues.apache.org/jira/browse/TEZ-3430
>             Project: Apache Tez
>          Issue Type: Bug
>            Reporter: Ming Ma
>            Assignee: Ming Ma
>         Attachments: TEZ-3430.patch
> The fair routing design in TEZ-3209 addresses the skewed partitions where one 
> partition could be much larger than the others. But to simplify the stats 
> tracking, it assumes a given partition's data is distributed evenly to some 
> degree across source tasks so that it can group consecutive source tasks 
> together.
> However, this assumption is invalid given {{MRInputHelpers}}'s 
> generateNewSplits and generateOldSplits sort the splits by size, thus the 
> data size in the beginning of source task range is bigger than that of at the 
> end.
> {noformat}
> Arrays.sort(splits, new InputSplitComparator());
> {noformat}
> One way to fix this is to have fair routing track not only the aggregated 
> size of each partition, but also the size of each partition of each source 
> task. But that will significantly increase the memory footprint.
> Alternatively, it can skip the sorting above. Test results for TEZ-3209 show 
> that jobs can finish 30% faster, given the source tasks output size is more 
> balanced.

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