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https://issues.apache.org/jira/browse/HADOOP-4035?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12643409#action_12643409
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Vivek Ratan commented on HADOOP-4035:
-------------------------------------
In HADOOP-4523, in my first comment, I've suggested the following, based on
feedback from some of our Ops folks:
bq. Another improvement is to let _mapred.tasktracker.tasks.maxmemory_ be set
by an external script, which lets Ops control what this value should be. A
slightly less desirable option, as indicated in some offline discussions with
Allen W, is to set this value to be an absolute number ("hadoop may use X
amount") or an offset of the total amount of memory on the machine ("hadoop may
use all but 4g").
Note that this value is suggested to be linked to total VM on the machine, not
RAM.
> Modify the capacity scheduler (HADOOP-3445) to schedule tasks based on memory
> requirements and task trackers free memory
> ------------------------------------------------------------------------------------------------------------------------
>
> Key: HADOOP-4035
> URL: https://issues.apache.org/jira/browse/HADOOP-4035
> Project: Hadoop Core
> Issue Type: Bug
> Components: contrib/capacity-sched
> Affects Versions: 0.19.0
> Reporter: Hemanth Yamijala
> Assignee: Vinod K V
> Priority: Blocker
> Fix For: 0.20.0
>
> Attachments: 4035.1.patch, HADOOP-4035-20080918.1.txt,
> HADOOP-4035-20081006.1.txt, HADOOP-4035-20081006.txt, HADOOP-4035-20081008.txt
>
>
> HADOOP-3759 introduced configuration variables that can be used to specify
> memory requirements for jobs, and also modified the tasktrackers to report
> their free memory. The capacity scheduler in HADOOP-3445 should schedule
> tasks based on these parameters. A task that is scheduled on a TT that uses
> more than the default amount of memory per slot can be viewed as effectively
> using more than one slot, as it would decrease the amount of free memory on
> the TT by more than the default amount while it runs. The scheduler should
> make the used capacity account for this additional usage while enforcing
> limits, etc.
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