[jira] [Commented] (CASSANDRA-1902) Migrate cached pages during compaction

["Jonathan Ellis (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-1902?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13010817#comment-13010817 ] 

Jonathan Ellis commented on CASSANDRA-1902:
-------------------------------------------

bq. BitSet is used in the BRAF to store pages that should be migrated (to avoid memory pressure). 

Would a bloom filter be even more memory-efficient?

> Migrate cached pages during compaction 
> ---------------------------------------
>
>                 Key: CASSANDRA-1902
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1902
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 0.7.1
>            Reporter: T Jake Luciani
>            Assignee: T Jake Luciani
>             Fix For: 0.8
>
>         Attachments: 0001-CASSANDRA-1902-cache-migration-impl-with-config-option.txt, 1902-formatted.txt, 1902-per-column-migration-rebase2.txt, 1902-per-column-migration.txt, CASSANDRA-1902-v3.patch, CASSANDRA-1902-v4.patch
>
>   Original Estimate: 32h
>          Time Spent: 56h
>  Remaining Estimate: 0h
>
> Post CASSANDRA-1470 there is an opportunity to migrate cached pages from a pre-compacted CF during the compaction process.  This is now important since CASSANDRA-1470 caches effectively nothing.  
> For example an active CF being compacted hurts reads since nothing is cached in the new SSTable. 
> The purpose of this ticket then is to make sure SOME data is cached from active CFs. This can be done my monitoring which Old SSTables are in the page cache and caching active rows in the New SStable.
> A simpler yet similar approach is described here: http://insights.oetiker.ch/linux/fadvise/

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