fair share scheduler causes unnecessary preemption under some conditions
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Key: MAPREDUCE-2027
URL: https://issues.apache.org/jira/browse/MAPREDUCE-2027
Project: Hadoop Map/Reduce
Issue Type: Bug
Components: contrib/fair-share
Reporter: Joydeep Sen Sarma
When the cluster hits speculative cap - JobInProgress does not speculate any
more. however FairShare Scheduler continues to believe that tasks need to be
speculated.
Under such conditions, FS Scheduler will start preempting repeatedly (because
from it's perspective - certain jobs are not getting the slots they deserve
(for speculative tasks)).
There may be other reasons for excessive preemption as well - this one stood
out clearly.
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