Hi, The read only version is not faster on reads compared to a writable store. Internally the only difference is we open files in read only mode.
The reason you get the error is that your OS does not support to place a memory mapped region to a file (opened in read only mode) when the region maps outside the file data (in write mode the file will grow in size when that happens). -Johan On Mon, Mar 29, 2010 at 9:03 PM, Marc Preddie <[email protected]> wrote: > Hi, > > I've had some time to look into this issue and it seems that when using the > "ReadOnly" versions of the classes, I get the memory mapping warnings and > when using the "Writable" versions of the classes, the warning does not > occur (I'm assuming memory mapping gets enabled). > > I'm not against using the "writable" versions of the classes; my only > concern is performance. Are the "readonly" versions faster that the > "writable" versions? And if they are; then if memory mapping is not enabled, > are they faster that the "writable" versions with memory mapping? > > I'll run some tests, but I guess I would like an expert opinion. > > Regards, > Marc > > On Mon, Mar 22, 2010 at 10:24 AM, Tobias Ivarsson < > [email protected]> wrote: > >> Hi, >> >> We have seen this message before emitted as a warning from Neo4j. Are you >> seing this as a warning as well, or are you getting an exception thrown to >> your application code? >> >> It's hard to deal with these errors since nio only throws IOException, and >> not any more semantic information than that, I believe we deal with all >> cases by issuing a warning and then falling back to another method of >> performing the same operation, but if you are getting exceptions we need to >> resolve it. If you are indeed getting exceptions, some code that triggers >> it >> would be very helpful. >> >> Cheers, >> Tobias >> >> On Wed, Mar 17, 2010 at 1:47 PM, Marc Preddie <[email protected]> wrote: >> >> > Hi, >> > >> > I've look at the mailing list and found 1 similar situation, but no real >> > solution. So I was hoping someone could shed some light on this. >> > >> > I seem to have an issue with neo4j being able to use memory mapped files. >> > I've run my service on Win XP 64bit, Mac OSX Snow Leopard 10.6.2 and >> Centos >> > 5.x 64bit and always get the same error when launching. I'm using APOC >> 1.0 >> > and have a DB of approx 600M. In my neo config I allocate about 5M more >> for >> > each type of file than the actual file size (I've tried multiple >> different >> > settings). On each machine I also leave at least 1.5G for the OS and have >> > at >> > least 2.5G heap for the Java process. I'm also using the >> > classes EmbeddedReadOnlyGraphDatabase and LuceneReadOnlyIndexService to >> > access and browse DB. >> > >> > Neo config >> > >> > neostore.nodestore.db.mapped_memory=10M >> > neostore.relationshipstore.db.mapped_memory=110M >> > neostore.propertystore.db.mapped_memory=85M >> > neostore.propertystore.db.index.mapped_memory=10M >> > neostore.propertystore.db.index.keys.mapped_memory=10M >> > neostore.propertystore.db.strings.mapped_memory=320M >> > neostore.propertystore.db.arrays.mapped_memory=10M >> > >> > Here is the error >> > >> > org.neo4j.kernel.impl.nioneo.store.MappedMemException: Unable to map >> > pos=3005872 recordSize=33 totalSize=1153416 >> > at >> > >> > >> org.neo4j.kernel.impl.nioneo.store.MappedPersistenceWindow.<init>(MappedPersistenceWindow.java:59) >> > at >> > >> > >> org.neo4j.kernel.impl.nioneo.store.PersistenceWindowPool.allocateNewWindow(PersistenceWindowPool.java:530) >> > at >> > >> > >> org.neo4j.kernel.impl.nioneo.store.PersistenceWindowPool.refreshBricks(PersistenceWindowPool.java:430) >> > at >> > >> > >> org.neo4j.kernel.impl.nioneo.store.PersistenceWindowPool.acquire(PersistenceWindowPool.java:122) >> > at >> > >> > >> org.neo4j.kernel.impl.nioneo.store.CommonAbstractStore.acquireWindow(CommonAbstractStore.java:459) >> > at >> > >> > >> org.neo4j.kernel.impl.nioneo.store.RelationshipStore.getChainRecord(RelationshipStore.java:248) >> > at >> > >> > >> org.neo4j.kernel.impl.nioneo.xa.NeoReadTransaction.getMoreRelationships(NeoReadTransaction.java:103) >> > at >> > >> > >> org.neo4j.kernel.impl.nioneo.xa.NioNeoDbPersistenceSource$ReadOnlyResourceConnection.getMoreRelationships(NioNeoDbPersistenceSource.java:275) >> > at >> > >> > >> org.neo4j.kernel.impl.persistence.PersistenceManager.getMoreRelationships(PersistenceManager.java:93) >> > at >> > >> > >> org.neo4j.kernel.impl.core.NodeManager.getMoreRelationships(NodeManager.java:585) >> > at >> > >> org.neo4j.kernel.impl.core.NodeImpl.getMoreRelationships(NodeImpl.java:332) >> > at >> > >> > >> org.neo4j.kernel.impl.core.NodeImpl.ensureFullRelationships(NodeImpl.java:320) >> > at >> > >> > >> org.neo4j.kernel.impl.core.NodeImpl.getAllRelationshipsOfType(NodeImpl.java:129) >> > at >> > >> > >> org.neo4j.kernel.impl.core.NodeImpl.getSingleRelationship(NodeImpl.java:179) >> > at >> > >> > >> org.neo4j.kernel.impl.core.NodeProxy.getSingleRelationship(NodeProxy.java:98) >> > .... >> > Caused by: java.io.IOException: Access is denied >> > at sun.nio.ch.FileChannelImpl.truncate0(Native Method) >> > at sun.nio.ch.FileChannelImpl.map(FileChannelImpl.java:728) >> > at >> > >> > >> org.neo4j.kernel.impl.nioneo.store.MappedPersistenceWindow.<init>(MappedPersistenceWindow.java:53) >> > ... 78 more >> > >> > >> > Regards >> > Marc _______________________________________________ Neo mailing list [email protected] https://lists.neo4j.org/mailman/listinfo/user
