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https://issues.apache.org/jira/browse/HDFS-6735?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Lars Hofhansl updated HDFS-6735:
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Attachment: HDFS-6735-v5.txt
Looked through the findbugs warning for DFSInputStream:
* indeed currentNode was wrongly synchronized (was so even before the patch).
In getCurrentDataNode I had added synchronized(infoLock) but getCurrentData
should just synchronized as currentNode is seek+read state.
* added a synchronized block in getBlockAt around access to pos, blockEnd,
currentLocatedBlock. As explained in comment that is not needed, since we never
get into that if block if we coming from a called synchronized on <this>. But
if that is so the extra synchronized won't hurt and it should make findbugs
happy.
> 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: Liang Xie
> Attachments: HDFS-6735-v2.txt, HDFS-6735-v3.txt, HDFS-6735-v4.txt,
> HDFS-6735-v5.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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