[jboss-jira] [JBoss JIRA] Commented: (JGRP-1043) UNICAST: high contention
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https://jira.jboss.org/jira/browse/JGRP-1043?page=com.atlassian.jira.plug...
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Bela Ban commented on JGRP-1043:
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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
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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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