Jason Brown created CASSANDRA-6995:
--------------------------------------
Summary: Execute local ONE/LOCAL_ONE reads on request thread
instead of dispatching to read stage
Key: CASSANDRA-6995
URL: https://issues.apache.org/jira/browse/CASSANDRA-6995
Project: Cassandra
Issue Type: Improvement
Components: Core
Reporter: Jason Brown
Assignee: Jason Brown
Priority: Minor
Fix For: 2.0.7
Attachments: syncread-stress.txt
When performing a read local to a coordinator node, AbstractReadExecutor will
create a new SP.LocalReadRunnable and drop it into the read stage for
asynchronous execution. If you are using a client that intelligently routes
read requests to a node holding the data for a given request, and are using
CL.ONE/LOCAL_ONE, the enqueuing SP.LocalReadRunnable and waiting for the
context switches (and possible NUMA misses) adds unneccesary latency. We can
reduce that latency and improve throughput by avoiding the queueing and thread
context switching by simply executing the SP.LocalReadRunnable synchronously in
the request thread. Testing on a three node cluster (each with 32 cpus, 132 GB
ram) yields ~10% improvement in throughput and ~20% speedup on avg/95/99
percentiles (99.9% was about 5-10% improvement).
--
This message was sent by Atlassian JIRA
(v6.2#6252)
