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Date: Thu, 27 Sep 2007 05:05:53 -0700 (PDT)
From: "Knut Anders Hatlen (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
Subject: [jira] Updated: (DERBY-2911) Implement a buffer manager using
 java.util.concurrent classes
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     [ https://issues.apache.org/jira/browse/DERBY-2911?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

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

    Attachment: d2911-6.stat
                d2911-6.diff

Attaching a new patch (d2911-6.diff) which implements a replacement algorithm using the interface and synchronization model described in the previous comments. The main part of the patch is the new ClockPolicy class and its rotateClock() method. I have done my best to state all requirements about synchronization and lock order in comments, so I hope it is possible for others to understand the code...

I manually edited modules.properties to enable the new buffer manager and ran the full regression test suite. suites.All ran successfully, whereas derbyall had one failure. The failure in derbyall was unit/T_RawStoreFactory.unit which has been mentioned before. This is an expected failure until reuse of invalid entries has been enabled for caches whose size is smaller than the maximum size.

I have not run any performance tests on this last patch, but I will do so. The performance test attached to this issue doesn't test the replacement algorithm since it creates just a small database. I will therefore see if I can run some other tests with different buffer sizes and also test it with update load, for instance using the test client attached to DERBY-1961.

What's left to do:
  - reuse Cacheable from invalid entries instead of growing the clock when size < maxSize (will fix the failure in unit/T_RawStoreFactory.unit)
  - implement a background cleaner
  - shrink the cache if it exceeds the maximum size

> 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-entry-javadoc.diff, d2911-unused.diff, d2911-unused.stat, d2911perf.java
>
>
> 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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