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https://issues.apache.org/jira/browse/DERBY-2911?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12529330
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Knut Anders Hatlen commented on DERBY-2911:
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Committed d2911-5 with revision 578006.
When I reran suites.All and derbyall with the new buffer manager enabled after
applying this patch, I only saw the expected failures in suites.All and two
failures in derbyall.
To find out which of the failures that are to be expected when the buffer
manager has no replacement algorithm, I ran the regression tests with the old
buffer manager modified so that the replacement algorithm wasn't used (that is,
I hard coded the Clock.maximumSize to Integer.MAX_VALUE). Then I saw the same
failures in suites.All, but only one failure in derbyall. That leaves us with
one "unexplained" error: unit/T_RawStoreFactory.unit which runs out of time.
> 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, d2911-3.diff,
> d2911-4.diff, d2911-5.diff, d2911-entry-javadoc.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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