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From "Robert Stupp (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-7438) Serializing Row cache alternative (Fully off heap)
Date Thu, 31 Jul 2014 10:26:39 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-7438?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14080708#comment-14080708
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Robert Stupp commented on CASSANDRA-7438:
-----------------------------------------

bq. Yeah it works in unix, but the problem is i don't have a handle since its a temp file
after restart. So it is a best effort for cleanups.

It's a really sick problem. I changed our Snappy integration a similar way. IMO there's no
better solution than "messing the temp dir".

bq. The problem is it produces a circular dependency

Ah - I meant that lruc code is copied to C* code base (if the others agree). But this could
be a second step since it's "only" a bit of refactoring.

> 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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