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https://issues.apache.org/jira/browse/HDFS-5851?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14007631#comment-14007631
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Todd Lipcon commented on HDFS-5851:
-----------------------------------
{quote}
>> The case of a local short circuit read having access to the open file is
>> interesting... does this pin the memory until the possibly misbehaved client
>> process closes the socket / FD?
> Yes this is correct. This should be the existing behavior with short-circuit
> reads.
{quote}
Not quite - it doesn't pin the memory, since the memory pinning is implemented
by the datanode calling "mlock". The datanode can still munlock the memory even
if the client holds the fd open, and the client will fall back to reading from
disk (through normal linux read path)
> Support memory as a storage medium
> ----------------------------------
>
> Key: HDFS-5851
> URL: https://issues.apache.org/jira/browse/HDFS-5851
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: datanode
> Affects Versions: 3.0.0
> Reporter: Arpit Agarwal
> Assignee: Arpit Agarwal
> Attachments:
> SupportingMemoryStorageinHDFSPersistentandDiscardableMemory.pdf,
> SupportingMemoryStorageinHDFSPersistentandDiscardableMemory.pdf
>
>
> Memory can be used as a storage medium for smaller/transient files for fast
> write throughput.
> More information/design will be added later.
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