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https://issues.apache.org/jira/browse/DERBY-2911?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Knut Anders Hatlen updated DERBY-2911:
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Attachment: d2911-7.diff
Attaching a new patch (d2911-7.diff) which implements reuse of free holder
objects if the maximum size of the cache has not been reached (it only touches
one file - ClockPolicy.java). The patch fixes the failure in
unit/T_RawStoreFactory.unit. I have also started the full regression test suite.
The failure in T_RawStoreFactory is still a mystery to me. I ended up with
scanning for free items backwards from the end of the clock. If the scan
started from the beginning, the test would fail. I suspect that either the test
does not test what it's supposed to test, or perhaps there is a bug somewhere,
but since I see the same failure if I change the scan direction in the old
buffer manager, I'm confident that the buffer manager is not the problem.
> 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, d2911-6.diff, d2911-6.stat, d2911-7.diff,
> d2911-entry-javadoc.diff, d2911-unused.diff, d2911-unused.stat,
> d2911perf.java, perftest6.pdf
>
>
> 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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