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https://issues.apache.org/jira/browse/DERBY-2911?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12543524
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Knut Anders Hatlen commented on DERBY-2911:
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Committed patch #8 with revision 596265.
Now the only thing that is not implemented, is shrinking the clock when it has
exceeded its maximum size (this happens if no evictable items are found by
rotateClock()). The old buffer manager would delegate the shrinking to its
daemon service from rotateClock() if it had a daemon service. If it didn't have
a daemon service, it would do the work itself from release(). I think we should
try the same approach for ConcurrentCache.
> 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: cleaner.diff, cleaner.tar, d2911-1.diff, d2911-1.stat,
> d2911-2.diff, d2911-3.diff, d2911-4.diff, d2911-5.diff, d2911-6.diff,
> d2911-6.stat, d2911-7.diff, d2911-7a.diff, d2911-entry-javadoc.diff,
> d2911-unused.diff, d2911-unused.stat, d2911perf.java, derby-2911-8.diff,
> derby-2911-8.stat, perftest6.pdf, poisson_patch8.tar
>
>
> 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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