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From "Pavel Yaskevich (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-5863) In process (uncompressed) page cache
Date Wed, 27 Apr 2016 22:49:13 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-5863?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15261121#comment-15261121
] 

Pavel Yaskevich commented on CASSANDRA-5863:
--------------------------------------------

+1 on the changes, much more readable now. Maybe one more nit from my original comments -
is there anyway we can change ChunkCache#invalidatePosition so instead of doing instance-of
checks and redirects to CachedRebufferer it simply does invalidate(new Key(...)), since ChunkReader
is effectively stateless maybe we could drop RebuffererFactory and use ChunkReader as a source
of all Rebufferers? This way IMHO it's clearer that ChunkReader is the source of the data
and doesn't have any bufferering, if buffering/caching is needed it can produce Rebufferer
which manages the memory, WDYT?

Also how do you want to proceed with this? After all of the changes can you squash/rebase,
so I can push?



> In process (uncompressed) page cache
> ------------------------------------
>
>                 Key: CASSANDRA-5863
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-5863
>             Project: Cassandra
>          Issue Type: Sub-task
>            Reporter: T Jake Luciani
>            Assignee: Branimir Lambov
>              Labels: performance
>             Fix For: 3.x
>
>
> Currently, for every read, the CRAR reads each compressed chunk into a byte[], sends
it to ICompressor, gets back another byte[] and verifies a checksum.  
> This process is where the majority of time is spent in a read request.  
> Before compression, we would have zero-copy of data and could respond directly from the
page-cache.
> It would be useful to have some kind of Chunk cache that could speed up this process
for hot data, possibly off heap.



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