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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DERBY-2911) Implement a buffer manager using java.util.concurrent classes
Date Tue, 02 Oct 2007 13:56:50 GMT

     [ https://issues.apache.org/jira/browse/DERBY-2911?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Knut Anders Hatlen updated DERBY-2911:
--------------------------------------

    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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