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https://issues.apache.org/jira/browse/CASSANDRA-5863?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13976380#comment-13976380
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Pavel Yaskevich commented on CASSANDRA-5863:
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[~jbellis] I tried to directly replace blocks of the compressed file with
uncompressed content (align all of the blocks to 64KB boundary effectively
creating file holes, mprotect some of the blocks to be writable, write
uncompressed contents), keeping per file block global heat map based on key
cache, but that didn't work out.
> In process (uncompressed) page cache
> ------------------------------------
>
> Key: CASSANDRA-5863
> URL: https://issues.apache.org/jira/browse/CASSANDRA-5863
> Project: Cassandra
> Issue Type: New Feature
> Components: Core
> Reporter: T Jake Luciani
> Assignee: Pavel Yaskevich
> Labels: performance
> Fix For: 2.1 beta2
>
>
> 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. Initially this could be a off heap cache but it would
> be great to put these decompressed chunks onto a SSD so the hot data lives on
> a fast disk similar to https://github.com/facebook/flashcache.
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