[jira] [Created] (HDFS-16891) Avoid the overhead of copy-on-write exception list while loading inodes sub sections in parallel

["Viraj Jasani (Jira)" <ji...@apache.org>]

Viraj Jasani created HDFS-16891:
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             Summary: Avoid the overhead of copy-on-write exception list while loading inodes sub sections in parallel
                 Key: HDFS-16891
                 URL: https://issues.apache.org/jira/browse/HDFS-16891
             Project: Hadoop HDFS
          Issue Type: Improvement
          Components: namenode
    Affects Versions: 3.3.4
            Reporter: Viraj Jasani
            Assignee: Viraj Jasani


If we enable parallel loading and persisting of inodes from/to fs image, we get the benefit of improved performance. However, while loading sub-sections INODE_DIR_SUB and INODE_SUB, if we encounter any errors, we use copy-on-write list to maintain the list of exceptions. Since our usecase is not to iterate over this list while executor threads are adding new elements to the list, using copy-on-write is bit of an overhead for this usecase.

It would be better to synchronize adding new elements to the list rather than having the list copy all elements over every time new element is added to the list.



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