Hello,

I am using IBM Cloudscape Version 10.0 with Hibernate 3.0 and it works great. But at the time I was deploying my project on a target with a Hyperthreating CPU things went wrong. It seems that Cloudscape is not stable on multiprocessor or Hyperthreating architectures. Both the reaction from developerworks:

http://www-128.ibm.com/developerworks/forums/dw_thread.jsp?message=13715134&cat=19&thread=80481&forum=370#13715134

and the Derby Jira:

http://issues.apache.org/jira/browse/DERBY-260?page=comments#action_64651

Indicated that the Cloudscape/Derby should work on multiprocessor or Hyperthreating architectures. This could mean a problem with Hibernate on multiprocessor or Hyperthreating architectures. Is Hibernate working on these architectures?

Regards,

Roland Beuker

The JVM is more likely to affect the stability on modern architectures than Java level code. I am not aware of any code in Hibernate that would be a problem. I have had projects (pre Hibernate) that were deployed on Multi-CPU hardware and became unstable - this was due to the hardware and its communications implementation between the CPUs etc. Deploy same app on alternate hardware turned out fine. The unstable hardware was fine if a CPU was pulled (it was a dual) so its down to a single CPU. There can be issues with modern processors in term of out of order byte code execution when code has (proven to be incorrect) optimisations such as certain locking (synchronisation) arrangements for singleton creation. There are a number of articles you can reference.

Your problem with an unstable Hibernate example seems to be the same as my problem. When I turn of Hyperthreating or the second CPU things are running fine, with Hyperthreating or more CPU’s my program is becoming unstable. This problem seems to be independent of the underlying database (tested with MySql, Jdatasore, Derby). I also tested on two different virtual machines: The standard Sun 1.5 JRE and Excelsion JET 3.7 (http://www.excelsior-usa.com/landing/jet-mem.html). On both virtual machines I experienced the same problem… Is the Hibernate code prepared for multiple CPU’s or dual core processing? This could be a problem with the upcoming dual core versions…

Hibernate uses standard Java code. It's the job of the VM to make the physical environment virtual. Your search should focus on that.

Christian is correct and backs what I said above. The JVM's implementation is the likely cause of any instability on modern processors. I would not expect and never found any issue with hibernate deployed on multi-processor platforms. I did (detailed above) have issues in the past on a non-hibernate project (that currently runs on a quad processor box) with certain hardware that did not implement its dual processor setup correctly. Today it is common and I have not found any issues since then (about 7 years ago). I would not expect any issues at all from dual-core processors.