Colin Patrick McCabe created HDFS-4953:
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Summary: enable HDFS local reads via mmap
Key: HDFS-4953
URL: https://issues.apache.org/jira/browse/HDFS-4953
Project: Hadoop HDFS
Issue Type: New Feature
Affects Versions: 2.2.0
Reporter: Colin Patrick McCabe
Assignee: Colin Patrick McCabe
Currently, the short-circuit local read pathway allows HDFS clients to access
files directly without going through the DataNode. However, all of these reads
involve a copy at the operating system level, since they rely on the read() /
pread() / etc family of kernel interfaces.
We would like to enable HDFS to read local files via mmap. This would enable
truly zero-copy reads.
In the initial implementation, zero-copy reads will only be performed when
checksums were disabled. Later, we can use the DataNode's cache awareness to
only perform zero-copy reads when we know that checksum has already been
verified.
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