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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: d2911-11.diff
Attaching a new patch which (d2911-11) which makes the new buffer manager use
the initialSize parameter in CacheFactory.newCacheManager(). It only uses the
parameter to specify the initial capacity of the ConcurrentHashMap in
ConcurrentCache and the ArrayList in ClockPolicy. The interface actually says
that we should create enough holder objects to hold that number of objects, but
that's not what the old buffer manager does. I have logged an issue DERBY-3275
for making the code and the comments match.
> 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,
> d2911-10.diff, d2911-10.stat, d2911-11.diff, d2911-2.diff, d2911-3.diff,
> d2911-4.diff, d2911-5.diff, d2911-6.diff, d2911-6.stat, d2911-7.diff,
> d2911-7a.diff, d2911-9.diff, d2911-9.stat, 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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