[jboss-jira] [JBoss JIRA] Resolved: (JGRP-457) Optimization: make threads return immediately if NAKACK has another active thread for the same sender

[Bela Ban (JIRA)]

     [ http://jira.jboss.com/jira/browse/JGRP-457?page=all ]

Bela Ban resolved JGRP-457.
---------------------------

    Resolution: Done

> Optimization: make threads return immediately if NAKACK has another active thread for the same sender
> -----------------------------------------------------------------------------------------------------
>
>                 Key: JGRP-457
>                 URL: http://jira.jboss.com/jira/browse/JGRP-457
>             Project: JGroups
>          Issue Type: Feature Request
>            Reporter: Bela Ban
>         Assigned To: Bela Ban
>            Priority: Minor
>             Fix For: 2.5
>
>
> In NAKACK, when a thread places a message for sender S into the NakReceiverWindow NRW, it subsequently acquires a lock on NRW (lock by sender) and removes as many messages as possible and passes them up.
> If many threads do this at the same time, all threads but one are blocked, and - when finally unblocked - usually return. This causes context switches and possibly cache flushing, so a better way would be to have the threads check whether another thread is already removing messages using a CAS operation *before* acquiring the lock.
> The effect should be that no threads will wait on the lock unnecessarily, and thus fewer context switches, and more threads available to the pool.

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