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From "Hudson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6735) A minor optimization to avoid pread() be blocked by read() inside the same DFSInputStream
Date Wed, 03 Dec 2014 11:47:15 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6735?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14232903#comment-14232903
] 

Hudson commented on HDFS-6735:
------------------------------

FAILURE: Integrated in Hadoop-Yarn-trunk #763 (See [https://builds.apache.org/job/Hadoop-Yarn-trunk/763/])
HDFS-6735. A minor optimization to avoid pread() be blocked by read() inside the same DFSInputStream
(Lars Hofhansl via stack) (stack: rev 7caa3bc98e6880f98c5c32c486a0c539f9fd3f5f)
* hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSInputStream.java
* hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
* hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/shortcircuit/ShortCircuitReplica.java
* hadoop-hdfs-project/hadoop-hdfs/dev-support/findbugsExcludeFile.xml
* hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/LocatedBlocks.java
* hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/shortcircuit/ShortCircuitCache.java


> A minor optimization to avoid pread() be blocked by read() inside the same DFSInputStream
> -----------------------------------------------------------------------------------------
>
>                 Key: HDFS-6735
>                 URL: https://issues.apache.org/jira/browse/HDFS-6735
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: hdfs-client
>    Affects Versions: 3.0.0
>            Reporter: Liang Xie
>            Assignee: Lars Hofhansl
>             Fix For: 2.7.0
>
>         Attachments: HDFS-6735-v2.txt, HDFS-6735-v3.txt, HDFS-6735-v4.txt, HDFS-6735-v5.txt,
HDFS-6735-v6.txt, HDFS-6735-v7.txt, HDFS-6735-v8.txt, HDFS-6735.txt
>
>
> In current DFSInputStream impl, there're a couple of coarser-grained locks in read/pread
path, and it has became a HBase read latency pain point so far. In HDFS-6698, i made a minor
patch against the first encourtered lock, around getFileLength, in deed, after reading code
and testing, it shows still other locks we could improve.
> In this jira, i'll make a patch against other locks, and a simple test case to show the
issue and the improved result.
> This is important for HBase application, since in current HFile read path, we issue all
read()/pread() requests in the same DFSInputStream for one HFile. (Multi streams solution
is another story i had a plan to do, but probably will take more time than i expected)



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