Re: [PATCH] mm, numa: Really disable NUMA balancing by default on single node machines

From: Rik van Riel
Date: Wed May 13 2015 - 09:08:09 EST

On 05/13/2015 04:10 AM, Mel Gorman wrote:
> NUMA balancing is meant to be disabled by default on UMA machines but
> the check is using nr_node_ids (highest node) instead of num_online_nodes
> (online nodes). The consequences are that a UMA machine with a node ID of 1
> or higher will enable NUMA balancing. This will incur useless overhead due
> to minor faults with the impact depending on the workload. These are the
> impact on the stats when running a kernel build on a single node machine
> whose node ID happened to be 1;
> vanilla patched
> NUMA base PTE updates 5113158 0
> NUMA huge PMD updates 643 0
> NUMA page range updates 5442374 0
> NUMA hint faults 2109622 0
> NUMA hint local faults 2109622 0
> NUMA hint local percent 100 100
> NUMA pages migrated 0 0
> Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx> #v3.8+

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

All rights reversed
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at