[jira] [Closed] (ASTERIXDB-1147) ConcurrentLockManager's performance bug when there are many locks on a single resource, such as dataset level lock

["Young-Seok Kim (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ASTERIXDB-1147?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Young-Seok Kim closed ASTERIXDB-1147.
-------------------------------------
    Resolution: Invalid

> ConcurrentLockManager's performance bug when there are many locks on a single resource, such as dataset level lock
> ------------------------------------------------------------------------------------------------------------------
>
>                 Key: ASTERIXDB-1147
>                 URL: https://issues.apache.org/jira/browse/ASTERIXDB-1147
>             Project: Apache AsterixDB
>          Issue Type: Bug
>            Reporter: Young-Seok Kim
>            Assignee: Till Westmann
>
> If a query scan a dataset which includes 1M records, the scan operator acquires 1M instantTryLocks. 
> Internally, ConcurrentLockManager holds 1M tryLocks in dataset level and 1M instantTryLocks in entity level. In other words, 1M dataset level locks are not released until the job is over. 
> If this situation happens, ConcurrentLockManager allocates 1M lockRequestSlots during lock acquiring phase and those slots are maintained in a linked list. Thus, when the job is over, those slots for the dataset level locks are released one at a time by searching each slot for each dataset level lock held by scanning the linked list. Thus, 1M slots of linked list is scanned 1M times. This is killing the scan performance. 



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