On 12/11/2015 09:30 AM, Steve Ebersole wrote: > It's hard to say without understanding the scenario where you are seeing > this as a problem. I have some guesses as to what may be the problem, > but without understanding more about why you see this as a problem in > the first place it is hard to give you an answer. For example, I wonder > if for environments not using multi-tenancy whether the recent changes > for the generators to support multi-tenancy might be the culprit. If > that is the case, and those changes are in fact the underlying cause of > the perf issues you see then I think there is actually a better > solution. But again, its hard to say unless we understand the reason > this "shows up" as a perf problem for you.
As best as I can tell from looking at the current PooledLoOptimizer, versus the proposed change (to have a chunk of ids per thread), we went from accessing a contented lock, to instead using per thread memory (eliminating the contended lock on PooledLoOptimizer.generate()). > > Until we hear more I think at this stage I'd vote for a separate > optimizer. And maybe even not one that is upstream. > > Also I agree with Scott that I am VERY leery of not cleaning up a > ThreadLocal. My mistake, as Stuart pointed out, the TL is not static, so we shouldn't introduce any leaks. > > On Fri, Dec 11, 2015 at 7:55 AM Scott Marlow <smar...@redhat.com > <mailto:smar...@redhat.com>> wrote: > > Should this be a specialized pooled optimizer that is only used in > environments that do not suffer from leaving the ThreadLocal around > after the application is undeployed? In other words, the expectation is > that classloader leaks with this pooled optimizer are expected (e.g. > user must restart the jvm to really undeploy the application > completely). > > I am thinking that there are at least three typical situations: > > 1. Applications are deployed in Java standalone edition. Generally, > when the app undeploys the jvm is shutting down. > > 2. Applications are deployed as part of some container (e.g. an EE > server) and the Hibernate jars are on the global classloader path (or > something like that). On each shared container thread, there would be > one Optimizer for all deployed applications. I wonder if instead, we > would want one Optimizer instance per Hibernate SessionFactory > associated with the many container threads? > > 3. Applications are deployed as part of some container (e.g. an EE > server) and the Hibernate jars are deployed with the application. The > ThreadLocals are associated with threads that are shared by different > deployed applications. The application classloader contains the > Hibernate classes. Each deployed application has its own Optimizer > threadlocal. On each shared container thread, there would be one > Optimizer per application (since each application has its Optimizer TL). > Like (2), there would be sharing of the same Optimizer with the many > application session factories. Should we instead have an optimizer per > session factory? > > Scott > > On 12/10/2015 11:31 PM, Stuart Douglas wrote: > > Hello, > > > > I have been working on a change to the pooled optimizer that we > have been seeing good performance results with. Basically it hands > out blocks of ID's to a thread local, rather than having every > thread contend on the lock every time an ID is required. > > > > > > https://github.com/hibernate/hibernate-orm/compare/master...stuartwdouglas:pooled-optimiser-hack > > > > What would I need to do to get a change like this in? In particular: > > > > - Does it need to be a new type of optimizer, or is modifying the > existing one like I have done OK? > > - How should it be configured? > > > > I am happy to do up a PR for this, but I am just not really sure > what would be required to get it to a point where it would be > acceptable for inclusion. > > > > Stuart > > _______________________________________________ > > hibernate-dev mailing list > > hibernate-dev@lists.jboss.org <mailto:hibernate-dev@lists.jboss.org> > > https://lists.jboss.org/mailman/listinfo/hibernate-dev > > > _______________________________________________ > hibernate-dev mailing list > hibernate-dev@lists.jboss.org <mailto:hibernate-dev@lists.jboss.org> > https://lists.jboss.org/mailman/listinfo/hibernate-dev > _______________________________________________ hibernate-dev mailing list hibernate-dev@lists.jboss.org https://lists.jboss.org/mailman/listinfo/hibernate-dev
