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From "Jing Zhao (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-5714) Use byte array to represent UnderConstruction feature and Snapshot feature for INodeFile
Date Fri, 03 Jan 2014 19:23:50 GMT
Jing Zhao created HDFS-5714:
-------------------------------

             Summary: Use byte array to represent UnderConstruction feature and Snapshot feature
for INodeFile
                 Key: HDFS-5714
                 URL: https://issues.apache.org/jira/browse/HDFS-5714
             Project: Hadoop HDFS
          Issue Type: Sub-task
            Reporter: Jing Zhao
            Assignee: Jing Zhao


Currently we define specific classes to represent different INode features, such as FileUnderConstructionFeature
and FileWithSnapshotFeature. While recording these feature information in memory, the internal
information and object references can still cost a lot of memory. For example, for FileWithSnapshotFeature,
not considering the INode's local name, the whole FileDiff list (with size n) can cost around
120n bytes.

In order to decrease the memory usage, we plan to use byte array to record the UnderConstruction
feature and Snapshot feature for INodeFile. Specifically, if we use protobuf's encoding, the
memory usage for a FileWithSnapshotFeature can be less than 56n bytes.



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