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Date: Wed, 6 Apr 2011 17:33:06 +0000 (UTC)
From: "T Jake Luciani (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
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Subject: [jira] [Commented] (CASSANDRA-1902) Migrate cached pages during
 compaction
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    [ https://issues.apache.org/jira/browse/CASSANDRA-1902?page=3Dcom.atlas=
sian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=3D=
13016453#comment-13016453 ]=20

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

Ok, reran on my box (4 core 4 gigs of ram). I also compared it to the previ=
ously committed version of this patch (v3)  I think v3 performs closer to t=
he 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 s=
wapped 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=20
#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,=E2=80=A6,  119, 40, 15

{noformat}

> Migrate cached pages during compaction=20
> ---------------------------------------
>
>                 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, CAS=
SANDRA-1902-v3.patch, CASSANDRA-1902-v4.patch, CASSANDRA-1902-v5.patch, CAS=
SANDRA-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 si=
nce CASSANDRA-1470 caches effectively nothing. =20
> For example an active CF being compacted hurts reads since nothing is cac=
hed in the new SSTable.=20
> 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 pa=
ge 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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