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From "Joshua McKenzie (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6890) Remove mmap'ed i/o from read path
Date Thu, 27 Mar 2014 14:53:17 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6890?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13949416#comment-13949416
] 

Joshua McKenzie commented on CASSANDRA-6890:
--------------------------------------------

Initial testing indicates a performance regression.  Just commenting out / changing the type
of SegmentedFile we're using is showing the #'s listed in my previous comment.  I'll be working
on getting clarity as to why this is taking place before moving forward on actually submitting
a patch to remove the functionality.

> Remove mmap'ed i/o from read path
> ---------------------------------
>
>                 Key: CASSANDRA-6890
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6890
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Joshua McKenzie
>            Assignee: Joshua McKenzie
>            Priority: Minor
>             Fix For: 3.0
>
>         Attachments: mmap_perf.txt
>
>
> Since we actively unmap unreferenced SSTR's and also copy data out of those readers on
the read path, the current memory mapped i/o is a lot of complexity for very little payoff.
 Clean out the mmapp'ed i/o on the read path.



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