Re: [RFC][PATCH 04/13] mm/numa: node demotion data structure and lookup

[David Rientjes]

On Mon, 25 Jan 2021, Dave Hansen wrote:

> diff -puN mm/migrate.c~0006-node-Define-and-export-memory-migration-path mm/migrate.c
> --- a/mm/migrate.c~0006-node-Define-and-export-memory-migration-path	2021-01-25 16:23:09.553866709 -0800
> +++ b/mm/migrate.c	2021-01-25 16:23:09.558866709 -0800
> @@ -1161,6 +1161,22 @@ out:
>  	return rc;
>  }
>  
> +static int node_demotion[MAX_NUMNODES] = {[0 ...  MAX_NUMNODES - 1] = NUMA_NO_NODE};

__read_mostly?

> +
> +/**
> + * next_demotion_node() - Get the next node in the demotion path
> + * @node: The starting node to lookup the next node
> + *
> + * @returns: node id for next memory node in the demotion path hierarchy
> + * from @node; NUMA_NO_NODE if @node is terminal.  This does not keep
> + * @node online or guarantee that it *continues* to be the next demotion
> + * target.
> + */
> +int next_demotion_node(int node)
> +{
> +	return node_demotion[node];
> +}
> +
>  /*
>   * Obtain the lock on page, remove all ptes and migrate the page
>   * to the newly allocated page in newpage.
> _
>