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https://issues.apache.org/jira/browse/HDFS-11634?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15969582#comment-15969582
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Konstantin Shvachko commented on HDFS-11634:
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Hey [~rushabh.shah], what I mean is that {{Iterator}} interface does not have
API to iterate backward or reset the iterator to a random member of a
collections.
The snippet you are referring to indeed loops back to the beginning, but that
should be pretty rare, when the initial random starting point was chosen too
close to the end of the list. I don't think we need to optimize the circular
jump. Do you?
> Optimize BlockIterator when interating starts in the middle.
> ------------------------------------------------------------
>
> Key: HDFS-11634
> URL: https://issues.apache.org/jira/browse/HDFS-11634
> Project: Hadoop HDFS
> Issue Type: Improvement
> Affects Versions: 2.6.5
> Reporter: Konstantin Shvachko
> Assignee: Konstantin Shvachko
> Attachments: HDFS-11634.001.patch, HDFS-11634.002.patch,
> HDFS-11634.003.patch, HDFS-11634.004.patch, HDFS-11643.005.patch
>
>
> {{BlockManager.getBlocksWithLocations()}} needs to iterate blocks from a
> randomly selected {{startBlock}} index. It creates an iterator which points
> to the first block and then skips all blocks until {{startBlock}}. It is
> inefficient when DN has multiple storages. Instead of skipping blocks one by
> one we can skip entire storages. Should be more efficient on average.
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