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From "Hemanth Yamijala (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4035) Modify the capacity scheduler (HADOOP-3445) to schedule tasks based on memory requirements and task trackers free memory
Date Tue, 30 Sep 2008 04:45:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4035?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12635652#action_12635652
] 

Hemanth Yamijala commented on HADOOP-4035:
------------------------------------------

The consensus on the implementation is as follows:

- Scheduler will assign tasks to a TT only if the amount of free memory is greater than the
task's requirements.
- If the memory requirements don't match, we do NOT move to the next job.
- We are not mapping tasks to slots at this point.

We understand point 3 means that the system is less fair than it should (because users of
high RAM jobs can cause more slots to go free than other jobs), but in the interest of keeping
things simple, we will follow this approach for Hadoop 0.19, and take it up in the future.

Note that if HADOOP-4306 is addressed, we will be handling scheduling w.r.to disk and memory
uniformly.

> 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: 0.19.0
>
>         Attachments: 4035.1.patch, HADOOP-4035-20080918.1.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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