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https://issues.apache.org/jira/browse/MAPREDUCE-3859?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13609117#comment-13609117
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Mike Roark commented on MAPREDUCE-3859:
---------------------------------------
Any updates on this bug? It is affecting us as well.. it has a pretty bad
effect on cluster utilization for these kinds of jobs. I tested this locally to
see if it was this issue, results below:
10 datanodes, each with 6 slots for reducers, 60 reducer slots total. No other
jobs running.
Running jobs in a queue which has "Reduce tasks, Capacity: 4 slots, Maximum
capacity: 60 slots"
Reducer sleeps for a while. This allows me to check steady state reducer slot
allocation.
||mapred.reduce.tasks||slots per reducer||expected running reduce
tasks||running reduce tasks||using slots||percent of capacity||notes||
|30|1|30|30|30|750| |
|30|2|30|{color:red}16{color}|32|800| |
|30|3|20|{color:red}1{color}|3|75| really bad |
|30|4|10|{color:red}8{color}|32|800| |
|30|5|10|{color:red}8{color}|40|1000| |
|30|6|10|{color:red}8{color}|48|1200| |
|30|7(err)|0|0|0|0| job hangs, but I expected this |
> CapacityScheduler incorrectly utilizes extra-resources of queue for
> high-memory jobs
> ------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-3859
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-3859
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: capacity-sched
> Affects Versions: 1.0.0
> Environment: CDH3u1
> Reporter: Sergey Tryuber
> Attachments: test-to-fail.patch.txt
>
>
> Imagine, we have a queue A with capacity 10 slots and 20 as extra-capacity,
> jobs which use 3 map slots will never consume more than 9 slots, regardless
> how many free slots on a cluster.
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