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https://issues.apache.org/jira/browse/CASSANDRA-1788?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12965783#action_12965783
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Gary Dusbabek commented on CASSANDRA-1788:
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Could you save another copy on send if packIt returned a Message augmented with
header information that would then be placed in the OutboundTcpConnection
queue? The consumer there would then take the message and serialize it
directly to the stream. The obvious disadvantage I see is that it shifts the
serialization work onto the writer thread, which might be undesirable.
> reduce copies on read, write paths
> ----------------------------------
>
> Key: CASSANDRA-1788
> URL: https://issues.apache.org/jira/browse/CASSANDRA-1788
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Jonathan Ellis
> Assignee: Jonathan Ellis
> Priority: Minor
> Fix For: 0.7.0
>
> Attachments: 1788.txt
>
>
> Currently, we do _three_ unnecessary copies (that is, writing to the socket
> is necessary; any other copies made are overhead) for each message:
> - constructing the Message body byte[] (this is typically a call to a
> ICompactSerializer[2] serialize method, but sometimes we cheat e.g. in
> SchemaCheckVerbHandler's reply)
> - which is copied to a buffer containing the entire Message (i.e. including
> Header) when sendOneWay calls Message.serializer.serialize()
> - which is copied to a newly-allocated ByteBuffer when sendOneWay calls packIt
> - which is what we write to the socket
> For deserialize we perform a similar orgy of copies:
> - IncomingTcpConnection reads the Message length, allocates a byte[], and
> reads the serialized Message into it
> - ITcpC then calls Message.serializer().deserialize, which allocates a new
> byte[] for the body and copies that part
> - finally, the verbHandler (determined by the now-deserialized Message
> header) deserializes the actual object represented by the body
> Most of these are out of scope for 0.7 but I think we can at least elide the
> last copy on the write path and the first on the read.
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