Daryn Sharp created HADOOP-9956:
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Summary: RPC listener inefficiently assigns connections to readers
Key: HADOOP-9956
URL: https://issues.apache.org/jira/browse/HADOOP-9956
Project: Hadoop Common
Issue Type: Sub-task
Components: ipc
Affects Versions: 2.0.0-alpha, 3.0.0
Reporter: Daryn Sharp
Assignee: Daryn Sharp
The socket listener and readers use a complex synchronization to update the
reader's NIO {{Selector}}. Updating active selectors is not thread-safe so
precautions are required.
However, the current locking choreography results in a serialized distribution
of new connections to the parallel socket readers. A slower/busier reader can
stall the listener and throttle performance.
The problem manifests as unexpectedly low cpu utilization by the listener and
readers (~20-30%) under heavy load. The call queue is shallow when it should
be overflowing.
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