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https://issues.apache.org/jira/browse/OPENJPA-474?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tim McConnell reassigned OPENJPA-474:
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Assignee: Tim McConnell
> Memory overhead by openjpa
> --------------------------
>
> Key: OPENJPA-474
> URL: https://issues.apache.org/jira/browse/OPENJPA-474
> Project: OpenJPA
> Issue Type: Bug
> Environment: Windows XP, Kodo 4.1.4, Sun JDK 1.6.2, ms sql server
> 2005, JTDS driver
> Reporter: Christiaan
> Assignee: Tim McConnell
> Attachments: testcase-memoryusage.zip
>
>
> I am doing some analysis for the memory usage since we are running into a
> couple of problems in our project when doing import of large quantities of
> objects. I've created a simple testcase which does the following:
> 1) Create all objects (2 classes, one class with 5 string attributes, the
> other is embedded and has no attributes);
> 2) Call makePersistent() on the objects;
> 3) Call commit();
> The results:
> - After step 1) takes up 23 mb of memory in the testcase;
> - After step 2) the memory usage has increased to 191 mb. Actually there are
> 3 scenarios I used:
> 1) Creating objects without the embedded class (which has no attributes, just
> an empty class): 75 mb
> 2) Creating objects with the embedded class instantiated: 180 mb;
> 3) Creating objects with the embedded class instantiated and after
> makePersistent() again instantiated (overwriting the previous value): 191 mb
> - During step 3) commit() the memory usage peaks at 580mb
> So,
> 1) to persist objects which take up 23mb of memory, a total of 580mb so
> giving a memory overhead of a factor 25 by the openjpa!
> 2) maintaining the datastructure whether objects are persistent increases the
> memory with a factor of 4 to 8, depending whether embeddable objects are
> used;
> 3) "overwriting" embedded objects within a transaction, the previous embedded
> object still seems to take up some memory;
> I haven't done a thorough analysis on this but some interesting things I
> noticed from the profiler:
> 1) One of the hotspots is in storing the RowImpl._sql. If I am not mistaken,
> this sql is stored (cached) for each object to be inserted. So in large
> transactions where a lot of similar objects and modifications are involved,
> this is quite a duplication which leads to unnecessary memory overhead. Of
> course there is a performance gain of caching it, but may be this should be
> better balanced with memory usage?;
> 2) Though I've set kodo.Log=none there is a hotspot in
> LoggingConnectionDecorator? Is this decorator used for something else as well
> or is this a bug? I removed it in code from DecoratingDatasource and this
> reduced the total memory usage to 500mb
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