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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 Fri, 12 Oct 2007 13:54:50 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: d2911-7a.diff

The attached patch 7a replaces patch 7. It implements reuse of free entries when the cache
is smaller than its max size. What's changed is that the scan for reusable entries is performed
by rotateClock() instead of a separate method. This means that we will also try to reuse free
entries when the cache is full and we know there is at least one free entry, even though we
didn't find a free or evictable entry after scanning 20% of the cache.

Derbyall and suites.All both ran cleanly with the new buffer manager enabled 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: 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, d2911-7a.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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