More improvement on block placement performance
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Key: HADOOP-5638
URL: https://issues.apache.org/jira/browse/HADOOP-5638
Project: Hadoop Core
Issue Type: Improvement
Components: dfs
Reporter: Hairong Kuang
Assignee: Hairong Kuang
Fix For: 0.21.0
Block placement algorithm currently has an excluded node list, which contains
all datanodes that have been visited. This list is implemented as an array
list, whose cost of inserting is O(1) but the cost of query "contains" is O(n),
where n is the number of datanodes. This makes the cost of block placement to
be O(n*n) when a cluster is full.
I propose to change the data structure of the excluded node list as a HashMap.
So in average, the cost of insertion is O(1) and the cost of query is O(1).
This makes the block placement algorithm to be O(n) in average.
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