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https://issues.apache.org/jira/browse/HDFS-2751?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13189795#comment-13189795
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Hudson commented on HDFS-2751:
------------------------------
Integrated in Hadoop-Mapreduce-trunk #964 (See
[https://builds.apache.org/job/Hadoop-Mapreduce-trunk/964/])
HDFS-2751. Datanode may incorrectly drop OS cache behind reads even for
short reads. Contributed by Todd Lipcon.
todd : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1233796
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/datanode/BlockSender.java
> Datanode drops OS cache behind reads even for short reads
> ---------------------------------------------------------
>
> Key: HDFS-2751
> URL: https://issues.apache.org/jira/browse/HDFS-2751
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: data-node
> Affects Versions: 0.23.0, 0.24.0
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Fix For: 0.24.0, 0.23.1
>
> Attachments: hdfs-2751.txt, hdfs-2751.txt
>
>
> HDFS-2465 has some code which attempts to disable the "drop cache behind
> reads" functionality when the reads are <256KB (eg HBase random access). But
> this check was missing in the {{close()}} function, so it always drops cache
> behind reads regardless of the size of the read. This hurts HBase random read
> performance when this patch is enabled.
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