[
https://issues.apache.org/jira/browse/MAPREDUCE-1845?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12882348#action_12882348
]
Matei Zaharia commented on MAPREDUCE-1845:
------------------------------------------
This looks good. Thanks for adding the unit tests too. We should check this
into 0.21 as well, if that's not out yet.
The only concern I have is that the existing unit tests, such as
testMinAndFairSharePreemption, work correctly. This seems to be because those
pools either only test one type of preemption (min-share or fair-share), or
they place the over-scheduled jobs in pools that have no min share set. This
means that one of the values in max(tasksDueToMinShare, tasksDueToFairShare) is
zero. Would you mind creating a second copy of testMinAndFairSharePreemption
where job 1 is in a pool with a min share set (i.e. not in the default pool)?
A minor comment on clarity: rather than adding the line "tasksToPreempt =
tasksToPreempt < 0 ? 0 : tasksToPreempt", it would be better to make sure that
tasksDueToMinShare and tasksDueToFairShare are themselves never negative. You
can do it by adding a max(0, ...) on the lines where they are computed (for
example, tasksDueToMinShare = Math.max(0, target - sched.getRunningTasks())).
> FairScheduler.tasksToPeempt() can return negative number
> --------------------------------------------------------
>
> Key: MAPREDUCE-1845
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-1845
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: contrib/fair-share
> Affects Versions: 0.22.0
> Reporter: Scott Chen
> Assignee: Scott Chen
> Fix For: 0.22.0
>
> Attachments: MAPREDUCE-1845.20100717.txt
>
>
> This method can return negative number. This will cause the preemption to
> under-preempt.
> The bug was discovered by Joydeep.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
