[hibernate-dev] Pooled Optimiser Improvements
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 https://lists.jboss.org/mailman/listinfo/hibernate-dev
Re: [hibernate-dev] Pooled Optimiser Improvements
- Original Message - > From: "Scott Marlow" > To: "Stuart Douglas" , hibernate-dev@lists.jboss.org > Sent: Friday, 11 December, 2015 10:54:15 PM > Subject: Re: [hibernate-dev] Pooled Optimiser Improvements > > 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. In this case it is a non-issue, as the JVM will be destroyed on shutdown. > > 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? AFAIK there is one optimiser per table, not one global optimiser. On undeploy these Optimisers will no longer be referenced and should be eligible for GC, which will clean up the thread local. It is importable to note that this is not a static thread local, which are very prone to leaks. > > 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? The same this applied here, once the application is undeployed the ThreadLocal should be eligible for GC. Stuart > > 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 > > 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
Re: [hibernate-dev] Pooled Optimiser Improvements
With my original patch the intention was that that the thread local blocks were smaller than the incrementSize, so not every thread local allocation would require a DB call. Your patch changes that approach but I don't think it actually matters that much, the overall performance should still be similar, and it has the advantage of not needed an extra configuration value. Stuart - Original Message - > From: "Scott Marlow" > To: "Steve Ebersole" , "Stuart Douglas" > , hibernate-dev@lists.jboss.org > Sent: Wednesday, 16 December, 2015 10:15:49 AM > Subject: Re: [hibernate-dev] Pooled Optimiser Improvements > > https://github.com/scottmarlow/hibernate-orm/commits/pooledOptimizer_5.x > is looking more correct now, if others want to look at that. > > On 12/15/2015 07:58 PM, Scott Marlow wrote: > > > > > > On 12/15/2015 05:58 PM, Scott Marlow wrote: > >> > >> > >> On 12/15/2015 05:40 PM, Scott Marlow wrote: > >>> I changed the new test methods a bit. [2] seems to be passed the tests > >>> but I am not understanding how PooledThreadLocalLoOptimizer should > >>> coordinate with the AccessCallback to allocate the next chunk of > >>> sequence numbers. > >>> > >>> We seem to be able to call AccessCallback.getNextValue() to get the next > >>> available sequence number but how do we reserve a block of 5000 sequence > >>> ids? Am I supposed to call callback.getNextValue() an extra time to get > >>> a range of values? Is there a separate database transaction that is > >>> used by the AccessCallback.getNextValue() calls? I'm missing something. > >> > >> Thinking more about this, I assume that AccessCallback.getNextValue() is > >> operating under a database transaction that we are probably ending > >> before AccessCallback.getNextValue() returns. It also sounds like the > >> database table is tracking the "lo" value, as mentioned in the > >> PooledLoOptimizer. This implies that only the application layer knows > >> what the range is. This seems like an important dependency to understand. > >> > >> Make sense? > > > > http://in.relation.to/2007/04/10/new-323-hibernate-identifier-generators > > seems to explain how increment_size is used. Since the user is already > > configured that, will look into switching to that for > > PooledThreadLocalLoOptimizer. > > > >> > >>> > >>> Note that [2] also includes a test change to comment out a few lines in > >>> SchemaUpdateDelimiterTest, due to the compiler error that I am seeing in > >>> intellij. Will need to remember to remove that change. > >>> > >>> [2] > >>> https://github.com/scottmarlow/hibernate-orm/commits/pooled-optimiser-hack-2 > >>> > >>> On 12/15/2015 12:36 PM, Steve Ebersole wrote: > >>>> Those tests tend to assert the increments. We seem to agree that this > >>>> ThreadLocal one can skip gaps of values. I'd look there first. > >>>> > >>>> > >>>> On Tue, Dec 15, 2015 at 11:34 AM Scott Marlow >>>> <mailto:smar...@redhat.com>> wrote: > >>>> > >>>>I'm trying to move the optimizer to PooledThreadLocalLoOptimizer > >>>>[1]. > >>>>We are currently failing some new unit tests, which are cloned > >>>>from > >>>>existing PooledLoOptimizer tests which might be part of the > >>>>problem. > >>>> > >>>>Scott > >>>> > >>>>[1] > >>>> > >>>> https://github.com/scottmarlow/hibernate-orm/tree/pooled-optimiser-hack > >>>> > >>>>On 12/14/2015 10:12 PM, Scott Marlow wrote: > >>>> > > >>>> > > >>>> > 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, >
