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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, 05 Sep 2007 08:20:34 GMT

    [ https://issues.apache.org/jira/browse/DERBY-2911?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12525012
] 

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

Thanks Manish, that's a great suggestion, but since the objects in the cache need to implement
the Cacheable interface and Cacheable.getIdentity() returns an Object, we're kind of locked
into declaring the hash key as Object. We could work around that problem by casting the identity
to the parametrized type K, like

    K key = (K) cacheable.getIdentity();
    cache.remove(key);

but that'll give us a compile-time warning about an unchecked cast. So until the interfaces
that we need to work with are rewritten using generics, I think it's best not to parametrize
the key type.

> 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
>         Attachments: d2911-1.diff, d2911-1.stat, d2911-2.diff, d2911-unused.diff, d2911-unused.stat,
d2911perf.java
>
>
> 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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