[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-5927) Performance risk: Suboptimal synchronization in org.hibernate.engine.query.QueryPlanCache.getHQLQueryPlan

From what I've read the Guava Cache uses a per-segment LRU algorithm for eviction so your LRU eviction behavior wouldn't be in strict LRU order but for a cache like this that seems ok.

Performance risk: Suboptimal synchronization in org.hibernate.engine.query.QueryPlanCache.getHQLQueryPlan --------------------------------------------------------------------------------------------------------- Key: HHH-5927 URL: https://hibernate.onjira.com/browse/HHH-5927 Project: Hibernate ORM Issue Type: Improvement Components: core Reporter: Strong Liu Assignee: Strong Liu Attachments: hotspot.png with Order Demo (real-life simulation attempt test app) I have noticed that there is thread contention on createNamesQuery() which sounds suspicious. After investigation it boils down to org.hibernate.engine.query.QueryPlanCache.getHQLQueryPlan. It serves as a cache (internal, not replacable) for queries using LRU algorithm (supplied from Apache utils). Generally speaking, blocking threads in any sort of caches indicates a problem. From about 2000 calls, 700 got blocked (which is also not nice for context switching). I guess, one of the problems is that there is exclusive synchronization in get method: public synchronized Object get(Object key) {...} which could be replaced by a more granular read-write lock. org/hibernate/engine/query/QueryPlanCache.java org/hibernate/util/SoftLimitMRUCache.java