[jboss-jira] [JBoss JIRA] (JGRP-1989) Bundlers: reuse send buffer when transport == sync.

[Bela Ban (JIRA)]

    [ https://issues.jboss.org/browse/JGRP-1989?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13134697#comment-13134697 ] 

Bela Ban commented on JGRP-1989:
--------------------------------

Another alternative is to always send the reusable buffer and copy at the {{TCP_NIO2}} level *if needed*. For example, if a write of 1000 bytes succeeds than we know that 1000 bytes have been written and the buffer can get reused.
If the write returns rc=800, then we know that we still need to write the final 200 bytes. In this case, we could *copy* the bytes in range {{buf[801..1000]}}. I assume that a TCP write would succeed in most cases, so this would not do a lot of copying.
Downside: an NIO write is done deep inside JGroups NIO ({{NioConnection}}), so we'd have to let this class somehow know whether or not to copy data. For instance, if a user always provides copied data in the first place, there'd be no need o copy at all.

> Bundlers: reuse send buffer when transport == sync.
> ---------------------------------------------------
>
>                 Key: JGRP-1989
>                 URL: https://issues.jboss.org/browse/JGRP-1989
>             Project: JGroups
>          Issue Type: Enhancement
>            Reporter: Bela Ban
>            Assignee: Bela Ban
>             Fix For: 3.6.7
>
>
> With the addition of {{TCP_NIO2}}, all bundlers now create new send buffers for every message (or message list). This generates a lot of memory allocations, perhaps it is better to revert this change for *synchronous transports* such as {{UDP}} and {{TCP}}, and still create new buffers for *asynchronous transports* such as {{TCP_NIO2}}.
> Synchronous transports guarantee a message has been put on the wire when {{TP.send()}} returns, whereas asynchronous transports may only have completed a partial write (so we cannot reuse the buffer).
> The code in the bundler should check for this, and copy if async or not copy if sync.
> Whether or not a transport is sync is determined by a new abstract method that needs to be overridden by every transport.



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