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https://issues.apache.org/jira/browse/HDFS-2476?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13134193#comment-13134193
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Steve Loughran commented on HDFS-2476:
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Tomasz, I've probably just possibly made your patch hard to apply in HDFS-2485
-but that won't impact your code at all. Can you merge your changes into trunk
and resubmit?
Like I said before, hadoop-common would be the best place for the structures as
the other parts of the system can pick them up there. That will mean
# splitting out the data structures and tests
# packaging under hadoop common and not hdfs.
# adding a (linked) hadoop common issue
> More CPU efficient data structure for
> under-replicated/over-replicated/invalidate blocks
> ----------------------------------------------------------------------------------------
>
> Key: HDFS-2476
> URL: https://issues.apache.org/jira/browse/HDFS-2476
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: name-node
> Reporter: Tomasz Nykiel
> Assignee: Tomasz Nykiel
> Attachments: hashStructures.patch, hashStructures.patch-2,
> hashStructures.patch-3, hashStructures.patch-4, hashStructures.patch-5
>
>
> This patch introduces two hash data structures for storing under-replicated,
> over-replicated and invalidated blocks.
> 1. LightWeightHashSet
> 2. LightWeightLinkedSet
> Currently in all these cases we are using java.util.TreeSet which adds
> unnecessary overhead.
> The main bottlenecks addressed by this patch are:
> -cluster instability times, when these queues (especially under-replicated)
> tend to grow quite drastically,
> -initial cluster startup, when the queues are initialized, after leaving
> safemode,
> -block reports,
> -explicit acks for block addition and deletion
> 1. The introduced structures are CPU-optimized.
> 2. They shrink and expand according to current capacity.
> 3. Add/contains/delete ops are performed in O(1) time (unlike current log n
> for TreeSet).
> 4. The sets are equipped with fast access methods for polling a number of
> elements (get+remove), which are used for handling the queues.
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