Mailing-List: contact commits-help@cassandra.apache.org; run by ezmlm
Precedence: bulk
Reply-To: dev@cassandra.apache.org
Message-ID: <8484259.178781295926663712.JavaMail.jira@thor>
Date: Mon, 24 Jan 2011 22:37:43 -0500 (EST)
From: "T Jake Luciani (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
Subject: [jira] Commented: (CASSANDRA-1902) Migrate cached pages during
 compaction
In-Reply-To: <32519327.13481293215925846.JavaMail.jira@thor>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit


    [ https://issues.apache.org/jira/browse/CASSANDRA-1902?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12986205#action_12986205 ] 

T Jake Luciani commented on CASSANDRA-1902:
-------------------------------------------

Oh, the setup above is on a 4 core Xen box with 4G ram the -S 3000 creates about 1.8G of data which is just enough to fit in the unused memory.

So if you test with a larger box be sure to up this.

> 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: 0.7.2
>
>         Attachments: 1902_v1.txt
>
>   Original Estimate: 32h
>          Time Spent: 24h
>  Remaining Estimate: 8h
>
> Post CASSANDRA-1470 there is an opportunity to migrate cached pages from a pre-compacted CF during the compaction process.  
> First, add a method to MmappedSegmentFile: long[] pagesInPageCache() that uses the posix mincore() function to detect the offsets of pages for this file currently in page cache.
> Then add getActiveKeys() which uses underlying pagesInPageCache() to get the keys actually in the page cache.
> use getActiveKeys() to detect which SSTables being compacted are in the os cache and make sure the subsequent pages in the new compacted SSTable are kept in the page cache for these keys. This will minimize the impact of compacting a "hot" SSTable.
> A simpler yet similar approach is described here: http://insights.oetiker.ch/linux/fadvise/

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.