Data node process consumes 180% cpu
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Key: HADOOP-2144
URL: https://issues.apache.org/jira/browse/HADOOP-2144
Project: Hadoop
Issue Type: Improvement
Reporter: Runping Qi
I did a test on DFS read throughput and found that the data node process
consumes up to 180% cpu when it is under heavi load. Here are the details:
The cluster has 380+ machines, each with 3GB mem and 4 cpus and 4 disks.
I copied a 10GB file to dfs from one machine with a data node running there.
Based on the dfs block placement policy, that machine has one replica for each
block of the file.
then I run 4 of the following commands in parellel:
hadoop dfs -cat thefile > /dev/null &
Since all the blocks have a local replica, all the read requests went to the
local data node.
I observed that:
The data node process's cpu usage was around 180% for most of the time .
The clients's cpu usage was moderate (as it should be).
All the four disks were working concurrently with comparable read
throughput.
The total read throughput was maxed at 90MB/Sec, about 60% of the expected
total
aggregated max read throughput of 4 disks (160MB/Sec)
The data node's cpu usage seems unreasonably high.
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