[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=12485889#action_12485889 ] 

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

The DelayQueue (based on PriorityQueue) used by ScheduledThreadPoolExecutor seems to be inefficient regarding adding and removing elements. These methods apparently need rebalancing of the tree.

ConcurrentSkipListSet promises log(n) cost for add() and remove(), maybe we should take a look at replacing ScheduledThreadPoolExecutor in TimeScheduler with this !

Disadvantage: ConcurrentSkipListSet requires JDK 6 as base line...

> 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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