[jira] [Commented] (CASSANDRA-7359) Optimize locking in PaxosState

["Benedict (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-7359?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14019171#comment-14019171 ] 

Benedict commented on CASSANDRA-7359:
-------------------------------------

It's probably a lot easier to either 1) simply expand the bucket range; or 2) use a ConcurrentHashMap and perform putIfAbsent with the exact hash, so that there is no limit to the number of concurrent operations

> Optimize locking in PaxosState
> ------------------------------
>
>                 Key: CASSANDRA-7359
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7359
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: sankalp kohli
>            Priority: Minor
>
> In PaxosState, we want to lock on same rows and have created 1024 size array with java Objects in them to be used for locking. 
> We should replace these Objects with some Lock so that we can know whether there is contention trying to acquire a lock for different rows.
> We can achieve that by also storing the hash of the row which acquired the lock. This will tell us if this needs to be improved. 
> Here is an improvement which I was thinking about. 
> Say two rows A and B map to the same 1024 bucket which we have. A get the lock and B has to wait. Here B can check if his hash is different and create a new object and chain it to the other one. 
> This looks close to a hashMap with chaining for same key. 
> The hard part will be removing the entries no longer being used.  



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