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From "Robert Stupp (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-7438) Serializing Row cache alternative (Fully off heap)
Date Sat, 01 Nov 2014 10:38:35 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-7438?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14193074#comment-14193074
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Robert Stupp commented on CASSANDRA-7438:
-----------------------------------------

bq. total 1 byte profit
bikeshed : could be two if serialized "unencoded" :)
I took some time to see whether it could be some lhf to change that - but it isn't really
(because there are some uses of {{DataIn/Output(Plus)}} that would need to be changed, too
- and it is used widely - even (if I saw that correctly) in SSTables (the point at which I
stopped investigating ;) )

> Serializing Row cache alternative (Fully off heap)
> --------------------------------------------------
>
>                 Key: CASSANDRA-7438
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7438
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>         Environment: Linux
>            Reporter: Vijay
>            Assignee: Vijay
>              Labels: performance
>             Fix For: 3.0
>
>         Attachments: 0001-CASSANDRA-7438.patch
>
>
> Currently SerializingCache is partially off heap, keys are still stored in JVM heap as
BB, 
> * There is a higher GC costs for a reasonably big cache.
> * Some users have used the row cache efficiently in production for better results, but
this requires careful tunning.
> * Overhead in Memory for the cache entries are relatively high.
> So the proposal for this ticket is to move the LRU cache logic completely off heap and
use JNI to interact with cache. We might want to ensure that the new implementation match
the existing API's (ICache), and the implementation needs to have safe memory access, low
overhead in memory and less memcpy's (As much as possible).
> We might also want to make this cache configurable.



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