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https://issues.apache.org/jira/browse/HADOOP-18296?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17959749#comment-17959749
]
ASF GitHub Bot commented on HADOOP-18296:
-----------------------------------------
steveloughran commented on PR #7732:
URL: https://github.com/apache/hadoop/pull/7732#issuecomment-2963095009
```
./hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/impl/TrackingByteBufferPool.java:101:
public static class LeakDetectorHeapByteBufferPoolException extends
RuntimeException {: Class LeakDetectorHeapByteBufferPoolException should be
declared as final. [FinalClass]
./hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/contract/AbstractContractVectoredReadTest.java:643:
TrackingByteBufferPool pool = TrackingByteBufferPool.wrap(getPool());:28:
'pool' hides a field. [HiddenField]
./hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/contract/AbstractContractVectoredReadTest.java:679:
LOG.info("Slicing is enabled; we saw leaked buffers: {} after {} releases
of unknown bufferfs",: Line is longer than 100 characters (found 101).
[LineLength]
```
> Memory fragmentation in ChecksumFileSystem Vectored IO implementation.
> ----------------------------------------------------------------------
>
> Key: HADOOP-18296
> URL: https://issues.apache.org/jira/browse/HADOOP-18296
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: common
> Affects Versions: 3.4.0
> Reporter: Mukund Thakur
> Assignee: Steve Loughran
> Priority: Minor
> Labels: fs, pull-request-available
>
> As we have implemented merging of ranges in the ChecksumFSInputChecker
> implementation of vectored IO api, it can lead to memory fragmentation. Let
> me explain by example.
>
> Suppose client requests for 3 ranges.
> 0-500, 700-1000 and 1200-1500.
> Now because of merging, all the above ranges will get merged into one and we
> will allocate a big byte buffer of 0-1500 size but return sliced byte buffers
> for the desired ranges.
> Now once the client is done reading all the ranges, it will only be able to
> free the memory for requested ranges and memory of the gaps will never be
> released for eg here (500-700 and 1000-1200).
>
> Note this only happens for direct byte buffers.
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