[ https://issues.apache.org/jira/browse/HDFS-4879?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Todd Lipcon updated HDFS-4879: ------------------------------ Attachment: hdfs-4879.txt New patch changes ChunkedArrayList to extend AbstractList, which just throws exceptions on unsupported operations. I also addressed the above feedback. Given that the list now implements the List interface, the patch is much smaller and I think much improved. Thanks for the review, folks. I ran TestLargeDirectoryDelete and it passed. > Add "blocked ArrayList" collection to avoid CMS full GCs > -------------------------------------------------------- > > Key: HDFS-4879 > URL: https://issues.apache.org/jira/browse/HDFS-4879 > Project: Hadoop HDFS > Issue Type: Improvement > Components: namenode > Affects Versions: 3.0.0, 2.0.4-alpha > Reporter: Todd Lipcon > Assignee: Todd Lipcon > Attachments: hdfs-4879.txt, hdfs-4879.txt, hdfs-4879.txt > > > We recently saw an issue where a large deletion was issued which caused 25M > blocks to be collected during {{deleteInternal}}. Currently, the list of > collected blocks is an ArrayList, meaning that we had to allocate a > contiguous 25M-entry array (~400MB). After a NN has been running for a long > amount of time, the old generation may become fragmented such that it's hard > to find a 400MB contiguous chunk of heap. > In general, we should try to design the NN such that the only large objects > are long-lived and created at startup time. We can improve this particular > case (and perhaps some others) by introducing a new List implementation which > is made of a linked list of arrays, each of which is size-limited (eg to 1MB). -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira