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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: d2911-10.stat
d2911-10.diff
Attaching a new patch (d2911-10). This patch addresses the potential deadlock
issue if user code (i.e., Cacheable.setIdentity() or
Cacheable.createIdentity()) reenters the cache. It makes the callers of
setIdentity()/createIdentity() release the ReentrantLock on the cache entry
before calling one of those methods. Other threads that want to access the
object in that entry therefore have to wait until the identity has been set,
whereas threads scanning the cache (e.g., checkpoint or clock rotation) skip
the entry instead of waiting since they just see an invalid/kept entry.
All the regression tests passed when I enabled ConcurrentCache in
modules.properties.
> 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, d2911-2.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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