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https://issues.apache.org/jira/browse/CASSANDRA-8464?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14250361#comment-14250361
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T Jake Luciani commented on CASSANDRA-8464:
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Why would there be an issue using mmaped data for compaction?
Throttling of compressed data is treated that way because it's in the aspect of
streaming or compaction which works on uncompressed data.
> Support direct buffer decompression for reads
> ---------------------------------------------
>
> Key: CASSANDRA-8464
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8464
> Project: Cassandra
> Issue Type: Improvement
> Reporter: T Jake Luciani
> Assignee: T Jake Luciani
> Labels: performance
> Fix For: 3.0
>
>
> Currently when we read a compressed sstable we copy the data on heap then
> send it to be de-compressed to another on heap buffer (albeit pooled).
> But now both snappy and lz4 (with CASSANDRA-7039) allow decompression of
> direct byte buffers. This lets us mmap the data and decompress completely
> off heap (and avoids moving bytes over JNI).
> One issue is performing the checksum offheap but the Adler32 does support in
> java 8 (it's also in java 7 but marked private?!)
> This change yields a > 10% boost in read performance on cstar. Locally I see
> upto 30% improvement.
> http://cstar.datastax.com/graph?stats=5ebcdd70-816b-11e4-aed6-42010af0688f&metric=op_rate&operation=2_read&smoothing=1&show_aggregates=true&xmin=0&xmax=200.09&ymin=0&ymax=135908.3
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