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From "Benedict (JIRA)" <j...@apache.org>
Subject [jira] [Assigned] (CASSANDRA-9379) Use a collection supporting more efficient removal in Ref.GlobalState
Date Thu, 09 Jul 2015 16:44:04 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-9379?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Benedict reassigned CASSANDRA-9379:
-----------------------------------

    Assignee: Benedict

> Use a collection supporting more efficient removal in Ref.GlobalState
> ---------------------------------------------------------------------
>
>                 Key: CASSANDRA-9379
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9379
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Benedict
>            Assignee: Benedict
>            Priority: Minor
>
> Ref is intended only to be used in places where there are very few Ref instances against
a given object extant at any moment, so this collection does not need to be performant. But
to avoid performance regressions, such as accidentally introduced in CASSANDRA-8897 (but avoidable
via the scaling back of Ref use, since no longer necessary), we could use a collection that
supports more efficient removal.
> I would prefer, however, not to use either of CHM or NBHM, since both are heavyweight
objects, wasting a lot of heap; the former is also blocking, and the latter could be problematic
for this kind of workload, since it can leave references present in the map after a deletion.
The most suitable structure is the one I blogged about [here|http://belliottsmith.com/eventual-consistency-concurrent-data-structures/]
and have on github [here|https://github.com/belliottsmith/bes-utils/blob/master/src/bes/concurrent/collections/SimpleCollection.java],
since it offers lock-free append and wait-free removal, and ensures space utilization is as
low as possible.
> Thoughts/opinions?



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