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T Jake Luciani commented on CASSANDRA-8464: ------------------------------------------- No, I don't think we would remove mmap for 3.0. And this ticket does allow mmapping of compressed 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 > > Attachments: compression_direct.png > > > 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 -- This message was sent by Atlassian JIRA (v6.3.4#6332)