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https://issues.apache.org/jira/browse/HDFS-354?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Allen Wittenauer resolved HDFS-354.
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Resolution: Fixed
I'm going to close this out as stale. There has been a lot of reworking of the
DN process so it isn't clear if this is still an issue. I'm going to go with
no.
> Data node process consumes 180% cpu
> ------------------------------------
>
> Key: HDFS-354
> URL: https://issues.apache.org/jira/browse/HDFS-354
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Runping Qi
> Assignee: Chris Douglas
>
> 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). Thus disks were
> not a bottleneck
> in this case.
> The data node's cpu usage seems unreasonably high.
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