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From "Ian Boston (JIRA)" <j...@apache.org>
Subject [jira] Commented: (JCR-2699) Improve read/write concurrency
Date Fri, 08 Oct 2010 12:29:31 GMT

    [ https://issues.apache.org/jira/browse/JCR-2699?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12919265#action_12919265
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Ian Boston commented on JCR-2699:
---------------------------------

The AccessControlProviderHolder attached here does put more pressure on the Heap than before
and we have seen it result in high GC levels as it extracts all the space it can out of the
JVM under heavy load (100 concurrent request threads).  There is an updated version being
maintained at http://github.com/ieb/open-experiments/blob/master/bundles/server/src/main/java/org/apache/jackrabbit/core/AccessControlProviderHolder.java
(for the record ASF License granted), this uses soft references and a reference queue to allow
the GC to evict SystemSessions when under pressure, although I found that this still put the
GC under undue pressure so it also explicitly evicts AccessControlProviders when they get
old and full ensuring that heap is never overloaded. Teste with Jmeter scripts over several
hours. Will make a brief comment on JCR-2573

> Improve read/write concurrency
> ------------------------------
>
>                 Key: JCR-2699
>                 URL: https://issues.apache.org/jira/browse/JCR-2699
>             Project: Jackrabbit Content Repository
>          Issue Type: Improvement
>          Components: jackrabbit-core
>            Reporter: Jukka Zitting
>            Assignee: Jukka Zitting
>             Fix For: 2.2.0
>
>         Attachments: AccessControlProviderHolder.java, ConcurrentReadTest.png, ConcurrentReadTest.png,
ConcurrentReadWriteTest.png, DynamicSecurityManager-JCR2699.patch
>
>
> I'd like to set up a few performance tests to help identify our worst bottlenecks for
various kinds of concurrent read-only and read-write access patterns.
> Once identified, I'm hoping to fix at least some of those bottlenecks.

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