[jboss-dev-forums] [Design of JBossCache] - Re: Should acquired locks be released in the order they were

[bdueck]

Folks;

This is a bit of a stale thread, but I do now have some data that confirms the change I proposed to TransactionEntry does indeed have a positive effect on scalability. My tests show it improves overall scalability by up to 6%. Some tests show no improvement, but none show degredation.

Can everyone please re-review the proposal below as well as the earlier posts in this thread? If there are no objections, I'll make the change this week.

anonymous wrote : 
  | org.jboss.cache.TransactionEntry
  | 	- changed TransactionEntry.locks from List based implementation to 
  | 	ConcurrentReaderHashMap. This avoids expensive linear scannng calls 
  | 	to locks.contains() in addLock() and also improves concurrency by 
  | 	avoiding blocking synchroized() calls where most of the access to 
  | 	locks is read-only. I'm using ConcurrentReaderHashMap here more as 
  | 	a Set than a Map since there is no value to store. We're really just
  | 	interested in efficient searches in locks and highly concurrent reads.
  | 	
  | 	- I'm not sure of the impact of this change on 
  | 	org.jboss.cache.interceptors.OptimisticLockingInterceptor and 
  | 	org.jboss.cache.interceptors.PessimisticLockInterceptor 
  | 	which might be relying on some implementation specifics of the order of 
  | 	insertion of entries into what getLocks() returns. Seems to me though 
  | 	that if they do have some sort of dependency on ordering that there 
  | 	should be a better way to deal with this...
  | 	
  | 	- this change impacts one public method - getLocks() which previously 
  | 	returned a java.util.List and now returns a java.util.Set. Only one test
  | 	is affected by this  (org.jboss.cache.cache.optimistic.OpLockingInterceptorTest) 
  | 	which depends on List.get(int) method that isn't available in Set.
  | 


Thanks,

Brian.

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