[jboss-jira] [JBoss JIRA] Commented: (JGRP-1104) Revisit critical path in NAKACK

[Vladimir Blagojevic (JIRA)]

    [ https://jira.jboss.org/jira/browse/JGRP-1104?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12496377#action_12496377 ] 

Vladimir Blagojevic commented on JGRP-1104:
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Vladimir:

If oob message is added to NRW it is immediately delivered by its own oob thread propelling that message up, right? So, what is the scenario when #1 occurs ?

Bela:

I forgot, but this *can* occur. That's why I wrote that code. I think the use case was the OOB message was dropped and then retransmitted (as reg message). 

> Revisit critical path in NAKACK
> -------------------------------
>
>                 Key: JGRP-1104
>                 URL: https://jira.jboss.org/jira/browse/JGRP-1104
>             Project: JGroups
>          Issue Type: Task
>    Affects Versions: 2.8
>            Reporter: Vladimir Blagojevic
>            Assignee: Vladimir Blagojevic
>             Fix For: 2.9
>
>
> Revisit NAKACK#handleMessage and see if we can:
> a) lower contention on NRW lock by not attempting to propel up oob messages one-by-one
> I have no profiling data so I am speaking without a solid proof to back my claims. I am envisioning both oob and regular threads contending for a window as they push messages up the stack. oob threads are always going to attempt to lock per message (line 788). In an event that we received missing oob message in a series of oob messages we are going to repeatedly lock window per message traversed. Not good. We don't need this IMHO. I really like lock efficient removeMany algorithm. Let removeMany propel messages up the stack as much as possible, even oob messages.
> b) why are we propelling oob messages on a timer (line 833)? Is it to lower the workload of the current thread, or is there a more fundamental reason?
> c) undelivered_msgs is complicating things unnecessarily IMHO. Why don't we let oob threads go into removeMany code and remove as much messages as they can - both oob and regular and push them up rather than lock NRW per message? 

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