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From "Pavel Yaskevich (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-4303) Compressed bloomfilters
Date Fri, 01 Jun 2012 16:18:23 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-4303?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13287509#comment-13287509
] 

Pavel Yaskevich commented on CASSANDRA-4303:
--------------------------------------------

In addition for it to be slower it's also not a good idea to mmap BF because you give all
cards to the kernel to page out contents of the BF in any moment necessary to handle other
I/O traffic which would lead to page faults on the critical BF operations in unpredictable
manner since memory mappings operate on the page cache basis.
                
> Compressed bloomfilters
> -----------------------
>
>                 Key: CASSANDRA-4303
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4303
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Brandon Williams
>             Fix For: 1.2
>
>
> Very commonly, people encountering an OOM need to increase their bloom filter false positive
ratio to reduce memory pressure, since BFs tend to be the largest shareholder.  It would make
sense if we could alleviate the memory pressure from BFs with compression while maintaining
the FP ratio (at the cost of a bit of cpu) that some users have come to expect.  One possible
implementation is at http://code.google.com/p/javaewah/

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