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https://issues.apache.org/jira/browse/HDFS-5182?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13891238#comment-13891238
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Colin Patrick McCabe commented on HDFS-5182:
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[~wheat9]: I think you're mixing up the two choices a little bit. choice #1
does pass the file descriptor, and use the shared memory segment for
communication. Choice #2 passes everything over UNIX domain sockets. SIGBUS
is not an issue since the shared memory segment is in memory (SIGBUS should
only happen on disk error). Virtual memory space is not an issue on 64-bit
machines. Portability is not an issue since Windows supports shared memory as
well, as you note.
> BlockReaderLocal must allow zero-copy reads only when the DN believes it's
> valid
> ---------------------------------------------------------------------------------
>
> Key: HDFS-5182
> URL: https://issues.apache.org/jira/browse/HDFS-5182
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs-client
> Affects Versions: 3.0.0
> Reporter: Colin Patrick McCabe
> Assignee: Colin Patrick McCabe
>
> BlockReaderLocal must allow zero-copy reads only when the DN believes it's
> valid. This implies adding a new field to the response to
> REQUEST_SHORT_CIRCUIT_FDS. We also need some kind of heartbeat from the
> client to the DN, so that the DN can inform the client when the mapped region
> is no longer locked into memory.
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