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https://issues.apache.org/jira/browse/CASSANDRA-1714?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12980966#action_12980966
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T Jake Luciani commented on CASSANDRA-1714:
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Still needs to copy MappedByteBuffers before row or key caching
See
http://download.oracle.com/javase/1.4.2/docs/api/java/nio/MappedByteBuffer.html
"All or part of a mapped byte buffer may become inaccessible at any time, for
example if the mapped file is truncated. An attempt to access an inaccessible
region of a mapped byte buffer will not change the buffer's content and will
cause an unspecified exception to be thrown either at the time of the access or
at some later time. It is therefore strongly recommended that appropriate
precautions be taken to avoid the manipulation of a mapped file by this
program, or by a concurrently running program, except to read or write the
file's content."
> zero-copy reads
> ---------------
>
> Key: CASSANDRA-1714
> URL: https://issues.apache.org/jira/browse/CASSANDRA-1714
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Jonathan Ellis
> Assignee: Pavel Yaskevich
> Fix For: 0.7.1
>
> Attachments: 1714-v5-07.txt, CASSANDRA-1714-0.7.patch,
> CASSANDRA-1714-v2.patch, CASSANDRA-1714-v3.patch,
> CASSANDRA-1714-v4-trunk.patch, CASSANDRA-1714.patch, zerocopy.txt
>
> Original Estimate: 32h
> Time Spent: 32h
> Remaining Estimate: 0h
>
> Since we are already using mmap'd ByteBuffers in MappedFileDataInput we
> should be able to do zero-copy reads (via buffer.slice()), which would give
> us better performance than CASSANDRA-1651 without having to worry about
> buffer management.
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