Todd Lipcon created HDFS-4418:
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Summary: HDFS-347: increase default FileInputStreamCache size
Key: HDFS-4418
URL: https://issues.apache.org/jira/browse/HDFS-4418
Project: Hadoop HDFS
Issue Type: Sub-task
Reporter: Todd Lipcon
Assignee: Todd Lipcon
The FileInputStreamCache currently defaults to holding only 10 input stream
pairs (corresponding to 10 blocks). In many HBase workloads, the region server
will be issuing random reads against a local file which is 2-4GB in size or
even larger (hence 20+ blocks).
Given that the memory usage for caching these input streams is low, and
applications like HBase tend to already increase their ulimit -n substantially
(eg up to 32,000), I think we should raise the default cache size to 50 or
more. In the rare case that someone has an application which uses local reads
with hundreds of open blocks and can't feasibly raise their ulimit -n, they can
lower the limit appropriately.
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