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From "Daniel John Debrunner (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-1704) Allow more concurrency in the lock manager
Date Mon, 13 Nov 2006 14:45:38 GMT
    [ http://issues.apache.org/jira/browse/DERBY-1704?page=comments#action_12449382 ] 
            
Daniel John Debrunner commented on DERBY-1704:
----------------------------------------------

I haven't had time to look at the patch  but the original intention was for there to be a
multi-thread lock manager
using multiple LockSets, e.g. a MultiPool implementation instead of a SinglePool implementation.
Just FYI.

With the multiple synchronization how is deadlock detection to be handled?

> Allow more concurrency in the lock manager
> ------------------------------------------
>
>                 Key: DERBY-1704
>                 URL: http://issues.apache.org/jira/browse/DERBY-1704
>             Project: Derby
>          Issue Type: Improvement
>          Components: Services, Performance
>    Affects Versions: 10.2.1.6
>            Reporter: Knut Anders Hatlen
>         Assigned To: Knut Anders Hatlen
>            Priority: Minor
>         Attachments: 1cpu.png, 2cpu.png, 8cpu.png, split-hashtables.diff, split-hashtables.stat
>
>
> I have seen indications of severe monitor contention in SinglePool
> (the current lock manager) when multiple threads access a Derby
> database concurrently. When a thread wants to lock an object, it needs
> to obtain the monitor for both SinglePool and LockSet (both of them
> are global synchronization points). This leads to poor scalability.
> We should investigate how to allow more concurrency in the lock
> manager, and either extend SinglePool or implement a new manager.

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