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From "Bryan Pendleton (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-2911) Implement a buffer manager using java.util.concurrent classes
Date Tue, 28 Aug 2007 17:35:31 GMT

    [ https://issues.apache.org/jira/browse/DERBY-2911?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12523288
] 

Bryan Pendleton commented on DERBY-2911:
----------------------------------------

Would a particular instantiation of the engine ever have more than
one buffer manager at a time? How (and why) would a user choose
one buffer manager implementation versus the other? Would it
be as simple as:
 - if this is JDK 1.5+, we always unconditionally use the new one
 - if this is JDK 1.4, we always unconditionally use the old one
Or is there some other reason that a user would want to override this?


> 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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