T Jake Luciani created CASSANDRA-8449:
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Summary: Allow zero-copy reads again
Key: CASSANDRA-8449
URL: https://issues.apache.org/jira/browse/CASSANDRA-8449
Project: Cassandra
Issue Type: Improvement
Reporter: T Jake Luciani
Priority: Minor
Fix For: 3.0
We disabled zero-copy reads in CASSANDRA-3179 due to in flight reads accessing
a ByteBuffer when the data was unmapped by compaction. Currently this code
path is only used for uncompressed reads.
The actual bytes are in fact copied to the client output buffers for both netty
and thrift before being sent over the wire, so the only issue really is the
time it takes to process the read internally.
This patch adds a slow network read test and changes the tidy() method to
actually delete a sstable once the readTimeout has elapsed giving plenty of
time to serialize the read.
Removing this copy causes significantly less GC on the read path and improves
the tail latencies:
http://cstar.datastax.com/graph?stats=c0c8ce16-7fea-11e4-959d-42010af0688f&metric=gc_count&operation=2_read&smoothing=1&show_aggregates=true&xmin=0&xmax=109.34&ymin=0&ymax=5.5
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