jackrabbit-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Manuel Molaschi (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (JCR-2892) Large fetch sizes have potentially deleterious effects on VM memory requirements when using Oracle
Date Mon, 05 Sep 2011 14:08:09 GMT

    [ https://issues.apache.org/jira/browse/JCR-2892?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13097151#comment-13097151
] 

Manuel Molaschi commented on JCR-2892:
--------------------------------------

We have a different problem with the same cause... We experience a big performance loss on
an app built on Magnolia CMS and starting on Tomcat (configured with xmx at 1024m)
After a long investigation we assumed that this behaviour was caused by jvm spending a lot
of time in GC (cpu usage was always very high)

These are the startup time on different jr versions / fetch size

with jr 2.2.1: 129 sec
with jr 2.2.8 (fetch size 10000): > 1h
with jr 2.2.8 (patch applied on ConnectionHelper to comment out stmt.setFetchSize): 135 sec

> Large fetch sizes have potentially deleterious effects on VM memory requirements when
using Oracle
> --------------------------------------------------------------------------------------------------
>
>                 Key: JCR-2892
>                 URL: https://issues.apache.org/jira/browse/JCR-2892
>             Project: Jackrabbit Content Repository
>          Issue Type: Bug
>          Components: jackrabbit-core, sql
>    Affects Versions: 2.2.2
>         Environment: Oracle 10g+
>            Reporter: Christopher Elkins
>
> Since Release 10g, Oracle JDBC drivers use the fetch size to allocate buffers for caching
row data.
> cf. http://www.oracle.com/technetwork/database/enterprise-edition/memory.pdf
> r1060431 hard-codes the fetch size for all ResultSet-returning statements to 10,000.
This value has significant, potentially deleterious, effects on the heap space required for
even moderately-sized repositories. For example, the BUNDLE table (from 'oracle.ddl') has
two columns -- NODE_ID raw(16) and BUNDLE_DATA blob -- which require 16 b and 4 kb of buffer
space, respectively. This requires a buffer of more than 40 mb [(16+4096) * 10000 = 41120000].
> If the issue described in JCR-2832 is truly specific to PostgreSQL, I think its resolution
should be moved to a PostgreSQL-specific ConnectionHelper subclass. Failing that, there should
be a way to override this hard-coded value in OracleConnectionHelper.

--
This message is automatically generated by JIRA.
For more information on JIRA, see: http://www.atlassian.com/software/jira

        

Mime
View raw message