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https://issues.apache.org/jira/browse/HDFS-13540?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16488398#comment-16488398
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Xiao Chen commented on HDFS-13540:
----------------------------------

Thanks a lot Sammi!

> DFSStripedInputStream should only allocate new buffers when reading
> -------------------------------------------------------------------
>
>                 Key: HDFS-13540
>                 URL: https://issues.apache.org/jira/browse/HDFS-13540
>             Project: Hadoop HDFS
>          Issue Type: Bug
>    Affects Versions: 3.0.0
>            Reporter: Xiao Chen
>            Assignee: Xiao Chen
>            Priority: Major
>             Fix For: 3.2.0, 3.1.1, 3.0.3
>
>         Attachments: HDFS-13540.01.patch, HDFS-13540.02.patch, 
> HDFS-13540.03.patch, HDFS-13540.04.patch, HDFS-13540.05.patch, 
> HDFS-13540.06.patch
>
>
> This was found in the same scenario where HDFS-13539 is caught.
> There are 2 OOM that looks interesting:
> {noformat}
> FSDataInputStream#close error:
> OutOfMemoryError: Direct buffer memoryjava.lang.OutOfMemoryError: Direct 
> buffer memory
>         at java.nio.Bits.reserveMemory(Bits.java:694)
>         at java.nio.DirectByteBuffer.<init>(DirectByteBuffer.java:123)
>         at java.nio.ByteBuffer.allocateDirect(ByteBuffer.java:311)
>         at 
> org.apache.hadoop.io.ElasticByteBufferPool.getBuffer(ElasticByteBufferPool.java:95)
>         at 
> org.apache.hadoop.hdfs.DFSStripedInputStream.resetCurStripeBuffer(DFSStripedInputStream.java:118)
>         at 
> org.apache.hadoop.hdfs.DFSStripedInputStream.closeCurrentBlockReaders(DFSStripedInputStream.java:205)
>         at 
> org.apache.hadoop.hdfs.DFSInputStream.close(DFSInputStream.java:672)
>         at 
> org.apache.hadoop.hdfs.DFSStripedInputStream.close(DFSStripedInputStream.java:181)
>         at java.io.FilterInputStream.close(FilterInputStream.java:181)
> {noformat}
> and 
> {noformat}
> org/apache/hadoop/fs/FSDataInputStream#unbuffer failed: error:
> OutOfMemoryError: Direct buffer memoryjava.lang.OutOfMemoryError: Direct 
> buffer memory
>         at java.nio.Bits.reserveMemory(Bits.java:694)
>         at java.nio.DirectByteBuffer.<init>(DirectByteBuffer.java:123)
>         at java.nio.ByteBuffer.allocateDirect(ByteBuffer.java:311)
>         at 
> org.apache.hadoop.io.ElasticByteBufferPool.getBuffer(ElasticByteBufferPool.java:95)
>         at 
> org.apache.hadoop.hdfs.DFSStripedInputStream.resetCurStripeBuffer(DFSStripedInputStream.java:118)
>         at 
> org.apache.hadoop.hdfs.DFSStripedInputStream.closeCurrentBlockReaders(DFSStripedInputStream.java:205)
>         at 
> org.apache.hadoop.hdfs.DFSInputStream.unbuffer(DFSInputStream.java:1782)
>         at 
> org.apache.hadoop.fs.StreamCapabilitiesPolicy.unbuffer(StreamCapabilitiesPolicy.java:48)
>         at 
> org.apache.hadoop.fs.FSDataInputStream.unbuffer(FSDataInputStream.java:230)
> {noformat}
> As the stack trace goes, {{resetCurStripeBuffer}} will get buffer from the 
> buffer pool. We could save the cost of doing so if it's not for a read (e.g. 
> close, unbuffer etc.)



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