[jboss-jira] [JBoss JIRA] Commented: (JGRP-1043) UNICAST: high contention

[Bela Ban (JIRA)]

    [ https://jira.jboss.org/jira/browse/JGRP-1043?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12485815#action_12485815 ] 

Bela Ban commented on JGRP-1043:
--------------------------------

Re:
>> 2) if(!added && !win.hasMessagesToRemove()) { // no ack if we didn't add the msg (e.g. duplicate)
>>               return;
>>           } 

Agreed, this code is not necessary, I removed it

> UNICAST: high contention
> ------------------------
>
>                 Key: JGRP-1043
>                 URL: https://jira.jboss.org/jira/browse/JGRP-1043
>             Project: JGroups
>          Issue Type: Task
>            Reporter: Bela Ban
>            Assignee: Bela Ban
>             Fix For: 2.6.13, 2.8
>
>
> If UNICAST receives a high number of messages *and* sends a high number of messages concurrently, there will be a lot of retransmissions. Reason is contention on 'connections', with up- and down messages accessing it concurrently. Both up- and down- messages impede each other and thus messages are not received in time, causing retransmissions (ACKs to be resent).
> SOLUTION:
> #1 Reduce contention and turn 'connections' from HashMap into ConcurrentHashMap
> #2 Break 'connections' into a send-table and receive-table: sends and acks access the send-table, receives the receive-table

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