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Hudson commented on HDFS-2477: ------------------------------ Integrated in Hadoop-Mapreduce-trunk #886 (See [https://builds.apache.org/job/Hadoop-Mapreduce-trunk/886/]) HDFS-2477. Optimize computing the diff between a block report and the namenode state. Contributed by Tomasz Nykiel. hairong : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1196676 Files : * /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt * /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockInfo.java * /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java * /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DatanodeDescriptor.java > Optimize computing the diff between a block report and the namenode state. > -------------------------------------------------------------------------- > > Key: HDFS-2477 > URL: https://issues.apache.org/jira/browse/HDFS-2477 > Project: Hadoop HDFS > Issue Type: Sub-task > Components: name-node > Reporter: Tomasz Nykiel > Assignee: Tomasz Nykiel > Fix For: 0.24.0 > > Attachments: reportDiff.patch, reportDiff.patch-2, > reportDiff.patch-3, reportDiff.patch-4, reportDiff.patch-5 > > > When a block report is processed at the NN, the BlockManager.reportDiff > traverses all blocks contained in the report, and for each one block, which > is also present in the corresponding datanode descriptor, the block is moved > to the head of the list of the blocks in this datanode descriptor. > With HDFS-395 the huge majority of the blocks in the report, are also present > in the datanode descriptor, which means that almost every block in the report > will have to be moved to the head of the list. > Currently this operation is performed by DatanodeDescriptor.moveBlockToHead, > which removes a block from a list and then inserts it. In this process, we > call findDatanode several times (afair 6 times for each moveBlockToHead > call). findDatanode is relatively expensive, since it linearly goes through > the triplets to locate the given datanode. > With this patch, we do some memoization of findDatanode, so we can reclaim 2 > findDatanode calls. Our experiments show that this can improve the reportDiff > (which is executed under write lock) by around 15%. Currently with HDFS-395, > reportDiff is responsible for almost 100% of the block report processing time. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa For more information on JIRA, see: http://www.atlassian.com/software/jira