Re: [PATCH 39/63] sched: numa: Use a system-wide search to find swap/migrationcandidates

[Rik van Riel]

On 10/07/2013 06:29 AM, Mel Gorman wrote:
> This patch implements a system-wide search for swap/migration candidates
> based on total NUMA hinting faults. It has a balance limit, however it
> doesn't properly consider total node balance.
> 
> In the old scheme a task selected a preferred node based on the highest
> number of private faults recorded on the node. In this scheme, the preferred
> node is based on the total number of faults. If the preferred node for a
> task changes then task_numa_migrate will search the whole system looking
> for tasks to swap with that would improve both the overall compute
> balance and minimise the expected number of remote NUMA hinting faults.
> 
> Not there is no guarantee that the node the source task is placed
> on by task_numa_migrate() has any relationship to the newly selected
> task->numa_preferred_nid due to compute overloading.
> 
> [riel@xxxxxxxxxx: Do not swap with tasks that cannot run on source cpu]
> Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Signed-off-by: Mel Gorman <mgorman@xxxxxxx>

Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>

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