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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DERBY-2327) Reduce monitor contention in LockSet
Date Tue, 13 Feb 2007 15:42:05 GMT

     [ https://issues.apache.org/jira/browse/DERBY-2327?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Knut Anders Hatlen updated DERBY-2327:

    Attachment: ConcurrentHashMap.diff

I agree that ConcurrentHashMap is the way to go. ConcurrentHashMap.diff is an experimental
patch which replaces the HashMap in LockSet with a ConcurrentHashMap. It seems to have good
effect on the 1000x10000 join load from DERBY-1961 on multi-CPUs. It doesn't come for free
in single-user environments though, but that could just as well be caused by stupid implementation
by me. Note that the patch is in a very experimental state. It runs, but exotic features like
deadlock detection certainly don't work. Also, in its current state it requires JDK6 to compile
and run.

> Reduce monitor contention in LockSet
> ------------------------------------
>                 Key: DERBY-2327
>                 URL: https://issues.apache.org/jira/browse/DERBY-2327
>             Project: Derby
>          Issue Type: Sub-task
>          Components: Performance, Services
>    Affects Versions:
>            Reporter: Knut Anders Hatlen
>            Priority: Minor
>         Attachments: ConcurrentHashMap.diff
> When multiple threads enter the lock manager, only one can access the hash table in LockSet.
To improve scalability on multiple CPUs, it should be possible to have more than one thread
accessing the lock table at the same time.

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