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From "Amir Langer (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-6658) Namenode memory optimization - Block replicas list
Date Thu, 28 Aug 2014 13:02:09 GMT

     [ https://issues.apache.org/jira/browse/HDFS-6658?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Amir Langer updated HDFS-6658:
------------------------------

    Attachment: BlockListOptimizationComparison.xlsx

Added comparison of memory with and without CompressedOops in both the original and modified
code.
(Memory in bytes collected using jmap).
Difference with compressed oops is marginal but significant without it.



> Namenode memory optimization - Block replicas list 
> ---------------------------------------------------
>
>                 Key: HDFS-6658
>                 URL: https://issues.apache.org/jira/browse/HDFS-6658
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: namenode
>    Affects Versions: 2.4.1
>            Reporter: Amir Langer
>            Assignee: Amir Langer
>         Attachments: BlockListOptimizationComparison.xlsx, Namenode Memory Optimizations
- Block replicas list.docx
>
>
> Part of the memory consumed by every BlockInfo object in the Namenode is a linked list
of block references for every DatanodeStorageInfo (called "triplets"). 
> We propose to change the way we store the list in memory. 
> Using primitive integer indexes instead of object references will reduce the memory needed
for every block replica (when compressed oops is disabled) and in our new design the list
overhead will be per DatanodeStorageInfo and not per block replica.
> see attached design doc. for details and evaluation results.



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