Georgi,
One of the first areas I would look at is the creation and destruction of
the EntityManagers. You mention that you are running with an extended
context, but does the application create or pool EntityManagers? Although
our testing has been with IBM databases, we have found that we get the best
performance with the minimum number of EntityManager creations. If you can
clear and reuse the EntityManagers, the overall performance will be better.

There is another cache that helps with sql generation as well. It has a
couple of restrictions, but if the majority of your queries are simple
findby operations, this cache will help considerably. The property is
QuerySQLCache and it is documented in the OpenJPA 1.2.x manual (
http://openjpa.apache.org/builds/1.2.0/apache-openjpa-1.2.0/docs/manual/manual.html#ref_guide_cache_querysql
).

Hope this helps with getting better performance.

Kevin

On Mon, Aug 25, 2008 at 3:21 PM, Georgi Naplatanov <gosho@(protected):

> Hello,
>
> I'm porting SQL/JDBC web application to JPA and i made some performance
> tests with PostgreSQL 8.3.3 and MySql 5.0.51a Community edition, with
> both - SQL/JDBC and OpenJPA implementations of the application.
>
>           Apache ab     Apache Jmeter
> PostgreSQL 8.3  -15%             -12%
> MySql 5.0.51a   -64%             -27%
>
> On both tests on PostgreSQL the performance loss is about 15% compared
> to pure SQL/JDBC implementation.
>
> On MySql the performance loss is very big especially on test with Apache
> ab utility.
>
> In the tests, OpenJPA 1.2.0 is configured with data cache enabled, query
> data cache disabled and query compilation cache - enabled. OpenJPA
> operates in extended context with Apache DBCP and statement pooling.
>
> Is this performance loss on MySql normal ? Does OpenJPA require some
> special configuration for MySql ?
>
> It is my persistence.xml file.
>
> <property name="openjpa.ConnectionProperties"
>                 value="DriverClassName=com.mysql.jdbc.Driver,
>                 Url=jdbc:mysql://localhost/mydb,
>                 Username=root,
>                 Password=123,
>                 maxActive=25,
>                 maxWait=25,
>                 minIdle=3,
>                 maxIdle=25,
>                 whenExhaustedAction=block,
>                 testOnBorrow=false,
>                 testWhileIdle=true,
>                 timeBetweenEvictionRunsMillis=3600000,
>                 numTestsPerEvictionRun=3,
>                 minEvictableIdleTime=1800000,
>                 testQuery=select 1,
>                 poolPreparedStatements=true"/>
>            <property name="openjpa.ConnectionDriverName"
>                 value="org.apache.commons.dbcp.BasicDataSource"/>
>
> <property name="openjpa.QueryCompilationCache" value="true"/>
> <property name="openjpa.QueryCache" value="false"/>
> <property name="openjpa.RemoteCommitProvider" value="sjvm"/>
> <property name="openjpa.DataCache" value="true(CacheSize=2000,
> SoftReferenceSize=0)"/>
> <property name="openjpa.FetchBatchSize" value="100"/>
> <property name="openjpa.ConnectionRetainMode" value="on-demand"/>
> <property name="openjpa.FlushBeforeQueries" value="true"/>
> <property name="openjpa.jdbc.DBDictionary"
>
> value="org.apache.openjpa.jdbc.sql.MySQLDictionary(SupportsSubselect=true)"/>
>
> Best regards
> Georgi
>