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Joydeep Sen Sarma commented on MAPREDUCE-1764: ---------------------------------------------- how expensive (memory wise) would it be to add indices from node->[tasks] and rack->[tasks] based on split information? leaving slots idle seems like a real bummer. it would seem better to be greedy and always grab something (especially if the fraction of non-local tasks is within tolerable limits) > FairScheduler locality delay may put heavy pressure on Jobtracker > ----------------------------------------------------------------- > > Key: MAPREDUCE-1764 > URL: https://issues.apache.org/jira/browse/MAPREDUCE-1764 > Project: Hadoop Map/Reduce > Issue Type: Bug > Affects Versions: 0.22.0 > Reporter: Scott Chen > Assignee: Dmytro Molkov > Fix For: 0.22.0 > > > FairScheduler locality delay feature holds the scheduling of jobs until it > gets good locality. > This greatly improves the locality of the tasks. Reduce the cost of traffic. > We have observed the following problem on FairScheduler locality delay: > We have some machines have older data and some newly added machines do not > have important data. > When these machines send heartbeat, JT scans tasks to find jobs has the right > locality. > Often time, these machines will scan all of the tasks of all the jobs and do > not get any tasks. > Scanning all the tasks on the JT is very costly. This makes JT very slow. > And these machines often time do not get scheduled. This hurts the cluster > utilization. > Any ideas? -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.