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From "T Jake Luciani (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-1902) Migrate cached pages during compaction
Date Wed, 06 Apr 2011 17:33:06 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1902?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13016453#comment-13016453
] 

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

Ok, reran on my box (4 core 4 gigs of ram). I also compared it to the previously committed
version of this patch (v3)  I think v3 performs closer to the way we want. it just needs to
perserve the page list similar to the way v7 does and migrate them all at the end, just before
the new sstables are swapped in.

{noformat}

./bin/stress -n 100000 -c 10 -S 1024 -k
(ON) 226
(OFF) 229
(OLDON) 230

#flush

./bin/stress -n 100000 -o read
(ON) 34, 15
(OFF) 80, 15
(OLDON) 80, 15

./bin/stress -n 100000 -c 10 -S 1024 -k
(ON) 226
(OFF) 228
(OLDON) 226

./bin/stress -n 100000 -o read
(ON) 15
(OFF) 110, 15
(OLDON) 75, 15

#compact 
#active reads
(ON) 110, 122, 153, 111, 66, 34, 96, 15
(OFF) 235, 134, 83, 60, 50, 90, 80, 20
(OLDON) 21, 15, 15, 15, 15, 15,…,  119, 40, 15

{noformat}

> 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: Pavel Yaskevich
>             Fix For: 0.7.5, 0.8
>
>         Attachments: 0001-CASSANDRA-1902-cache-migration-impl-with-config-option.txt,
1902-BufferedSegmentedFile-logandsleep.txt, 1902-formatted.txt, 1902-per-column-migration-rebase2.txt,
1902-per-column-migration.txt, CASSANDRA-1902-v3.patch, CASSANDRA-1902-v4.patch, CASSANDRA-1902-v5.patch,
CASSANDRA-1902-v6.patch, CASSANDRA-1902-v7.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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