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

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Message-ID: <6115c2e-99b7-75f7-f0dd-bc44e69e21e7@google.com>
Date:   Sat, 30 Jan 2021 17:19:28 -0800 (PST)
From:   David Rientjes <rientjes@...gle.com>
To:     Dave Hansen <dave.hansen@...ux.intel.com>
cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        yang.shi@...ux.alibaba.com, ying.huang@...el.com,
        dan.j.williams@...el.com, david@...hat.com, osalvador@...e.de
Subject: Re: [RFC][PATCH 04/13] mm/numa: node demotion data structure and
 lookup

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.
> _
>