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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-2911) Implement a buffer manager using java.util.concurrent classes
Date Wed, 29 Aug 2007 06:49:30 GMT

    [ https://issues.apache.org/jira/browse/DERBY-2911?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12523478
] 

Knut Anders Hatlen commented on DERBY-2911:
-------------------------------------------

Thanks for your comments, Dan and Bryan.

I was thinking about using Derby's module loader, which would basically do what Bryan says.
With JDK 1.4 or J2ME, the old one is used, and with JDK 1.5+ the new one. It is possible to
override the default by specifying -Dderby.module.cacheManager=org.apache.derby... on the
command line, but only when using sane builds, I think. Except for the obvious case where
there is a bug in the new implementation, I don't think users would want to override it. The
one thing I can think of, is if the old implementation performs better for a certain load/configuration.

> Implement a buffer manager using java.util.concurrent classes
> -------------------------------------------------------------
>
>                 Key: DERBY-2911
>                 URL: https://issues.apache.org/jira/browse/DERBY-2911
>             Project: Derby
>          Issue Type: Improvement
>          Components: Performance, Services
>    Affects Versions: 10.4.0.0
>            Reporter: Knut Anders Hatlen
>            Assignee: Knut Anders Hatlen
>            Priority: Minor
>
> There are indications that the buffer manager is a bottleneck for some types of multi-user
load. For instance, Anders Morken wrote this in a comment on DERBY-1704: "With a separate
table and index for each thread (to remove latch contention and lock waits from the equation)
we (...) found that org.apache.derby.impl.services.cache.Clock.find()/release() caused about
5 times more contention than the synchronization in LockSet.lockObject() and LockSet.unlock().
That might be an indicator of where to apply the next push".
> It would be interesting to see the scalability and performance of a buffer manager which
exploits the concurrency utilities added in Java SE 5.

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