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SubjectRe: [PATCH 17/18] sched: Retry migration of tasks to CPU on a preferred node
On Thu, Aug 01, 2013 at 10:43:27AM +0530, Srikar Dronamraju wrote:
> * Mel Gorman <mgorman@suse.de> [2013-07-15 16:20:19]:
>
> > When a preferred node is selected for a tasks there is an attempt to migrate
> > the task to a CPU there. This may fail in which case the task will only
> > migrate if the active load balancer takes action. This may never happen if
>
> Apart from load imbalance or heavily loaded cpus on the preferred node,
> what could be the other reasons for migration failure with
> migrate_task_to()?

These were the reasons I expected that migration might fail.

> I see it almost similar to active load balance except
> for pushing instead of pulling tasks.
>
> If load imbalance is the only reason, do we need to retry? If the task
> is really so attached to memory on that node, shouldn't we getting
> task_numa_placement hit before the next 5 seconds?
>

Depends on the PTE scanning rate.

--
Mel Gorman
SUSE Labs


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