[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-2645) Synchronization bottleneck in EntityModeToTuplizerMapping

[Diego Pires Plentz (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-2645?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_28596 ] 

Diego Pires Plentz commented on HHH-2645:
-----------------------------------------

Just to remember, we can't use java 5+ features, since we must sill compatible with java 1.4(at least)

> Synchronization bottleneck in EntityModeToTuplizerMapping
> ---------------------------------------------------------
>
>                 Key: HHH-2645
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2645
>             Project: Hibernate3
>          Issue Type: Patch
>          Components: core
>    Affects Versions: 3.2.3, 3.2.4, 3.2.4.sp1
>         Environment: Hibernate 3.2.3 (and later), Sun's JDK 1.4.2_12 (server VM) on SunOS 5.10, Oracle 10g R2
>            Reporter: Erik Bergersjö
>            Assignee: Gail Badner
>            Priority: Minor
>         Attachments: concurrentreader.patch
>
>
> We have had a major performance bottleneck in EntityModeToTuplizerMapping with Hibernate version 3.2.3 and the code for that class in 3.2.4sp1 is unchanged. We have found a solution that solves the issue and would like to get it into the real version. I submitted to the user forum first and was asked to create a JIRA issue.
> The problematic line is:
> private final Map tuplizers = Collections.synchronizedMap( new SequencedHashMap() );
> We have changed it to (using util.concurrent):
> private final Map tuplizers = new EDU.oswego.cs.dl.util.concurrent.ConcurrentReaderHashMap();
> This change alone makes our use cases six times faster. The difference is that ConcurrentReaderHashMap handles concurrent readers much better, they don't have to wait for each other.
> The problem occurs when a high number of threads try to initialize sets (see mapping below). A thread dump showed a high number of threads waiting for the same monitor, see partial stack trace below.
> The code runs on Sun's JDK 1.4.2_12 (server VM) on SunOS 5.10 and the kernel spends a lot of time handling mutexes with the original implementation. That time disappears from the radar screen with the fixed version.
> Example mapping for set:
> [code]
> <set name="lines" lazy="true"  inverse="true" cascade="all-delete-orphan">
>   <key>
>       <column name="col1" not-null="true" />
>       <column name="col2" not-null="true" />
>    </key>
>    <one-to-many class="LineClass" />
> </set>
> [/code]
> Stack trace (partial):
> "Thread-108" prio=5 tid=0x05852e90 nid=0x103 waiting for monitor entry [0x3ed7e000..0x3ed7fc28]
>         at java.util.Collections$SynchronizedMap.get(Collections.java:1942)
>         - waiting to lock <0x89d30788> (a java.util.Collections$SynchronizedMap)
>         at org.hibernate.tuple.EntityModeToTuplizerMapping.getTuplizerOrNull(EntityModeToTuplizerMapping.java:53)
>         at org.hibernate.tuple.EntityModeToTuplizerMapping.getTuplizer(EntityModeToTuplizerMapping.java:66)
>         at org.hibernate.type.ComponentType.getPropertyValues(ComponentType.java:353)
>         at org.hibernate.type.ComponentType.isEqual(ComponentType.java:141)
>         at org.hibernate.engine.CollectionKey.equals(CollectionKey.java:50)
>         at java.util.HashMap.eq(HashMap.java:274)
>         at java.util.HashMap.get(HashMap.java:323)
>         at org.hibernate.engine.loading.CollectionLoadContext.getLocalLoadingCollectionEntry(CollectionLoadContext.java:163)
>         at org.hibernate.engine.loading.CollectionLoadContext.locateLoadingCollectionEntry(CollectionLoadContext.java:150)
>         at org.hibernate.engine.loading.CollectionLoadContext.getLoadingCollection(CollectionLoadContext.java:92)
>         at org.hibernate.loader.Loader.readCollectionElement(Loader.java:1003)
>         at org.hibernate.loader.Loader.readCollectionElements(Loader.java:646)
>         at org.hibernate.loader.Loader.getRowFromResultSet(Loader.java:591)
>         at org.hibernate.loader.Loader.doQuery(Loader.java:701)
>         at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:236)
>         at org.hibernate.loader.Loader.loadCollection(Loader.java:1994)
>         at org.hibernate.loader.collection.CollectionLoader.initialize(CollectionLoader.java:36)
>         at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:565)
>         at org.hibernate.event.def.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:60)
>         at org.hibernate.impl.SessionImpl.initializeCollection(SessionImpl.java:1716)
>         at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:344)
>         at org.hibernate.collection.AbstractPersistentCollection.read(AbstractPersistentCollection.java:86)
>         at org.hibernate.collection.PersistentSet.iterator(PersistentSet.java:163)
>  

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