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https://issues.apache.org/jira/browse/HDFS-2495?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13568711#comment-13568711
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Hudson commented on HDFS-2495:
------------------------------
Integrated in Hadoop-Hdfs-0.23-Build #512 (See
[https://builds.apache.org/job/Hadoop-Hdfs-0.23-Build/512/])
merge -r 1199023:1199024 Merging from trunk to branch-0.23 to fix HDFS-2495
(Revision 1441249)
Result = SUCCESS
kihwal : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1441249
Files :
* /hadoop/common/branches/branch-0.23
*
/hadoop/common/branches/branch-0.23/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
*
/hadoop/common/branches/branch-0.23/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java
*
/hadoop/common/branches/branch-0.23/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestBlockManager.java
> Increase granularity of write operations in ReplicationMonitor thus reducing
> contention for write lock
> ------------------------------------------------------------------------------------------------------
>
> Key: HDFS-2495
> URL: https://issues.apache.org/jira/browse/HDFS-2495
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: namenode
> Affects Versions: 0.23.0
> Reporter: Tomasz Nykiel
> Assignee: Tomasz Nykiel
> Fix For: 2.0.0-alpha, 0.23.7
>
> Attachments: replicationMon.patch, replicationMon.patch-1
>
>
> For processing blocks in ReplicationMonitor
> (BlockManager.computeReplicationWork), we first obtain a list of blocks to be
> replicated by calling chooseUnderReplicatedBlocks, and then for each block
> which was found, we call computeReplicationWorkForBlock. The latter processes
> a block in three stages, acquiring the writelock twice per call:
> 1. obtaining block related info (livenodes, srcnode, etc.) under lock
> 2. choosing target for replication
> 3. scheduling replication (under lock)
> We would like to change this behaviour and decrease contention for the write
> lock, by batching blocks and executing 1,2,3, for sets of blocks, rather than
> for each one separately. This would decrease the number of writeLock to 2,
> from 2*numberofblocks.
> Also, the info level logging can be pushed outside the writelock.
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