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Posted to commits@cassandra.apache.org by "Jonathan Ellis (JIRA)" <ji...@apache.org> on 2011/04/12 15:26:05 UTC

[jira] [Commented] (CASSANDRA-2459) move SSTableScanner to use SSTableReader.dfile instead of BRAF

    [ https://issues.apache.org/jira/browse/CASSANDRA-2459?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13018824#comment-13018824 ] 

Jonathan Ellis commented on CASSANDRA-2459:
-------------------------------------------

(a) we still need to avoid pushing hot rows out w/ our sequential scan; it seems to me that using the same source as the read stage makes this harder, not easier.

> move SSTableScanner to use SSTableReader.dfile instead of BRAF
> --------------------------------------------------------------
>
>                 Key: CASSANDRA-2459
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2459
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Pavel Yaskevich
>            Assignee: Pavel Yaskevich
>             Fix For: 1.0
>
>
> That can give us the following benefits:
> a). don't need to skip a cache because we will be operating on memory mappings
> b). better performance (not copying data between kernel and user buffers as effect gained from using memory mapped segments, avoiding time operating on the kernel mode (+ time for switching context and read-ahead pressure) which BRAF involves)
> c). less impact on the live-reads
> d). less garbage will be created
> e). less file descriptors opened

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