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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-5939) Cache Providers calculate very different row sizes
Date Fri, 30 Aug 2013 14:25:52 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-5939?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13754721#comment-13754721
] 

Jonathan Ellis commented on CASSANDRA-5939:
-------------------------------------------

bq. we have removed CLHM in 2.0

Yup.  The cost/benefit of spending time on CLHM just isn't there for me.  Especially as the
guy who argued we should remove row cache entirely. :)

Unless you are planning to dig in, Chris, I propose we wontfix.
                
> Cache Providers calculate very different row sizes
> --------------------------------------------------
>
>                 Key: CASSANDRA-5939
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-5939
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>         Environment: 1.2.8
>            Reporter: Chris Burroughs
>            Assignee: Vijay
>
> Took the same production node and bounced it 4 times comparing version and cache provider.
 ConcurrentLinkedHashCacheProvider and SerializingCacheProvider produce very different results
resulting in an order of magnitude difference in rows cached.  In all cases the row cache
size was 2048 MB.  Hit rate is provided for color, but entries & size are the important
part.
> 1.2.8 ConcurrentLinkedHashCacheProvider:
>  * entries: 23,217
>  * hit rate: 43%
>  * size: 2,147,398,344
> 1.2.8 about 20 minutes of SerializingCacheProvider:
>  * entries: 221,709
>  * hit rate: 68%
>  * size: 18,417254
> 1.2.5 ConcurrentLinkedHashCacheProvider:
>  * entries: 25,967
>  * hit rate: ~ 50%
>  * size:  2,147,421,704
> 1.2.5 about 20 minutes of SerializingCacheProvider:
>  * entries: 228,457
>  * hit rate: ~ 70%
>  * size: 19,070,315
> A related(?) problem is that the ConcurrentLinkedHashCacheProvider sizes seem to be highly
variable.  Digging up the values for 5 different nodes in the cluster using ConcurrentLinkedHashCacheProvider
shows a wide variance in number of entries:
>  * 12k
>  * 444k
>  * 10k
>  * 25k
>  * 25k

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