[hibernate-issues] [Hibernate-JIRA] Reopened: (HHH-2175) L2 Cache performance is very very bad when writing other kinds of objects in the same transaction

L2 Cache performance is very very bad when writing other kinds of objects in the same transaction ------------------------------------------------------------------------------------------------- Key: HHH-2175 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2175 Project: Hibernate3 Type: Improvement

Components: core Versions: 3.2.0.ga Environment: Hibernate Entity Manager 3.2.0 + Annotations + Core Reporter: Sami Dalouche

Hibernate L2 Cache performance is very slow when writing objects in the same transaction. For instance. Let's say we have 2 completly unrelated classes A and B let's say A never changes, and we write tons of instances of B to the database. Both A and B are managed by the cache, but into differet cache regions (with different Ehcache configurations). So, let's consider a simple example like : loop 1: for(int i = 0 ; i < 10000 ; i++){ new A(); } and loop2: for(int i = 0 ; i < 10000 ; i++){ aDao.findAByKey("key"); } Since the L2 cache + Query cache is activatedon a + findAByKey, loop2's performance is comparable to loop's 1 one. It's pretty much the same, so everything is fine, so far. Let's call X the time taken by loop1 or loop2, that we consider equal. Now, let's consider loop3 and loop4: loop 3: for(int i = 0 ; i < 10000 ; i++){ new A(); bDao.save(new B()); } and loop4: for(int i = 0 ; i < 10000 ; i++){ aDao.findAByKey("key"); bDao.save(new B()); } So, now, let's consider that saving bDao.save(new B()) takes Y seconds for 10,000 iterations. You would expect loop3 and loop4 to have the same performance, roughly , X + Y, right ? Well, actually, loop3 takes X + Y. But loop4 takes around 20 * (X + Y) !!!!!!! (on my machine, so it can be slighly different). But you see the point : there is a HUGE difference of performance. I am sure there are design reasons for this, that's why I set this bug as an enhancement.. So, 2 things : * either it is possible to solve this issue, and it would be nice to correct it * either it is not possible to solve this issue, and it would be nice to add a section in the reference manual, explaining why hibernate behaves that way. Regards, Sami Dalouche