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https://issues.apache.org/jira/browse/HADOOP-18296?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17957045#comment-17957045
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ASF GitHub Bot commented on HADOOP-18296:
-----------------------------------------
steveloughran opened a new pull request, #7732:
URL: https://github.com/apache/hadoop/pull/7732
### Description of PR
* Lets you turn off checksumming in local fs (but not hdfs!) with option
`file.verify-checksum`
* Has copy of Parquet's `TrackingByteBufferAllocator`, modified for Hadoop
APIs and named
`TrackingByteBufferPool`; not yet used in tests.
* New capability "fs.capability.vectoredio.sliced" to declare that you slice
buffers.
### How was this patch tested?
no tests yet.
### For code changes:
- [X] Does the title or this PR starts with the corresponding JIRA issue id
(e.g. 'HADOOP-17799. Your PR title ...')?
- [ ] Object storage: have the integration tests been executed and the
endpoint declared according to the connector-specific documentation?
- [ ] If adding new dependencies to the code, are these dependencies
licensed in a way that is compatible for inclusion under [ASF
2.0](http://www.apache.org/legal/resolved.html#category-a)?
- [ ] If applicable, have you updated the `LICENSE`, `LICENSE-binary`,
`NOTICE-binary` files?
> 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
>
> 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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