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https://issues.apache.org/jira/browse/HADOOP-5638?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Hairong Kuang updated HADOOP-5638:
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Description:
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.
was:
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.
> More improvement on block placement performance
> -----------------------------------------------
>
> 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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