Re: [PATCH 11/19] sched/numa: Restrict migrating in parallel to the same node.

Rik van Riel
2018-06-04T17:59:32Z

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On Mon, 2018-06-04 at 15:30 +0530, Srikar Dronamraju wrote:
> Since task migration under numa balancing can happen in parallel,
> more
> than one task might choose to move to the same node at the same time.
> This can cause load imbalances at the node level.
>
> The problem is more likely if there are more cores per node or more
> nodes in system.
>
> Use a per-node variable to indicate if task migration
> to the node under numa balance is currently active.
> This per-node variable will not track swapping of tasks.

> The commit does cause some performance regression but is needed from
> a fairness/correctness perspective.

Does it help any "real workloads", even simple things
like SpecJBB2005?

If this patch only causes regressions, and does not help
any workloads, I would argue that it is not in fact needed.

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