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Posted to commits@cassandra.apache.org by "Benedict (JIRA)" <ji...@apache.org> on 2015/02/20 18:56:13 UTC

[jira] [Commented] (CASSANDRA-8160) CF level option to call posix_fadvise for sstables on creation and startup

    [ https://issues.apache.org/jira/browse/CASSANDRA-8160?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14329267#comment-14329267 ] 

Benedict commented on CASSANDRA-8160:
-------------------------------------

What's the rationale here? This only seems to make sense if the dataset is smaller than memory? And even then, using FADV_SEQUENTIAL seems unhelpful. All that offers is the OS the opportunity to _evict_ pages since it thinks we're done with them. WILLNEED asks it _not_ to, but it may do so at the expense of pages it really should retain.

> CF level option to call posix_fadvise for sstables on creation and startup
> --------------------------------------------------------------------------
>
>                 Key: CASSANDRA-8160
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8160
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Core
>            Reporter: Matt Stump
>            Assignee: Branimir Lambov
>            Priority: Minor
>             Fix For: 2.1.4
>
>         Attachments: trunk-8160.txt
>
>
> We should have a CF level configuration with will result in posix_fadvise being called for sstables for that CF. It should be called on node startup and for new sstables. This should be configurable per CF to allow for some CFs to be prioritized above others. Not sure if we should use POSIX_FADV_SEQUENTIAL or POSIX_FADV_WILLNEED. 



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