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https://issues.apache.org/jira/browse/HADOOP-4035?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12643071#action_12643071
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Owen O'Malley commented on HADOOP-4035:
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I guess that would work, but in general it works better if we have ratios 
instead since they automatically scale as hardware improves. It would also need 
to support negative values, if you want to allocate more than ram (obviously 
into swap or assuming that the tasks won't actually use it). I suspect that in 
most cases, it would be negative, which seems less user-friendly.

> 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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