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Posted to commits@cassandra.apache.org by "T Jake Luciani (JIRA)" <ji...@apache.org> on 2014/12/11 22:14:13 UTC

[jira] [Created] (CASSANDRA-8464) Support direct buffer decompression for reads

T Jake Luciani created CASSANDRA-8464:
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             Summary: 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
             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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