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

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

     [ https://issues.apache.org/jira/browse/CASSANDRA-7359?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Aleksey Yeschenko reassigned CASSANDRA-7359:
--------------------------------------------

    Assignee: Aleksey Yeschenko  (was: Benedict)

> Optimize locking in PaxosState
> ------------------------------
>
>                 Key: CASSANDRA-7359
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7359
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: sankalp kohli
>            Assignee: Aleksey Yeschenko
>            Priority: Minor
>             Fix For: 2.1.0
>
>         Attachments: 7359-2.txt, 7359.txt
>
>
> 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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