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