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https://issues.apache.org/jira/browse/HDFS-13540?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16478871#comment-16478871
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SammiChen commented on HDFS-13540:
----------------------------------
[~xiaochen], thanks for the explanation. It makes sense to change the Jira
title as your proposal. I double checked the code, *curStripeBuf* is only used
in two EC read functions.
For the new test case, I would suggest,
# change the name from testCloseDoesNotGetBuffer to
testCloseDoesNotAllocateNewBuffer. It's more clear.
# the test case always passes even when I use "true" in
closeCurrentBlockReaders. Because the *curStripeBuf* will be set to *null*
after *stream.close* is called. So *assertNull(stream.getCurStripeBuf());*
always stands.
The alternative to check whether buffer is allocated or not is to check the
number of buffers holds by *ElasticByteBufferPool*.
> DFSStripedInputStream should not allocate new buffers during close / unbuffer
> -----------------------------------------------------------------------------
>
> 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
> Attachments: HDFS-13540.01.patch, HDFS-13540.02.patch,
> HDFS-13540.03.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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