[jira] [Reopened] (CASSANDRA-6692) AtomicBTreeColumns Improvements

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

     [ https://issues.apache.org/jira/browse/CASSANDRA-6692?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Aleksey Yeschenko reopened CASSANDRA-6692:
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> AtomicBTreeColumns Improvements
> -------------------------------
>
>                 Key: CASSANDRA-6692
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6692
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Benedict
>            Assignee: Benedict
>            Priority: Minor
>              Labels: easyfix, performance
>             Fix For: 2.1
>
>
> There are two improvements to make to the BTree code that should help:
> 1) It turns out Stack Allocation is more rubbish than we had hoped, and so the fast route actually allocates garbage. It's unlikely this reduces throughput, but the increased young-gen pressure is probably unwelcome. I propose to remove the fast route for now.
> 2) It is not uncommon to race to perform an update, so that the new values are actually out-of-date when we come to modify the tree. In this case the update should recognise that the original (portion of) the tree has not been modified, and simply return it, without allocating a new one.



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