Re: [PATCH] change zonelist order v5 [2/3] automatic configuration

[Lee Schermerhorn <Lee.Schermerhorn@hp.com>]

On Tue, 2007-05-08 at 20:18 +0900, KAMEZAWA Hiroyuki wrote:
> Add auto zone ordering configuration.
> 
> This function will select ZONE_ORDER_NODE when
> 
> There are only ZONE_DMA or ZONE_DMA32.
> || size of (ZONE_DMA/DMA32) > (System Total Memory)/2
> || Assume Node(A)
> 	Node (A) is enough big &&
> 	Node (A)'s ZONE_DMA/DMA32 occupies 60% of Node(A)'s memory.
> 	(In this case, ZONE_ORDER_ZONE may not offer enough locality...)
> 
> otherwise, ZONE_ORDER_ZONE is selected.
> 
> Maybe there is no best and simple way to configure zone order. I wrote this base on
> my experience and discussion on the list.
> 
> Anyway, a user can specifiy zone order from boot option/sysctl.
> 
> Signed-Off-By: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 

Acked-by:  Lee Schermerhorn <lee.schermerhorn@hp.com>

> ---
>  mm/page_alloc.c |   51 +++++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 49 insertions(+), 2 deletions(-)
> 
> Index: linux-2.6.21-mm1/mm/page_alloc.c
> ===================================================================
> --- linux-2.6.21-mm1.orig/mm/page_alloc.c
> +++ linux-2.6.21-mm1/mm/page_alloc.c
> @@ -2248,8 +2248,55 @@ static void build_zonelists_in_zone_orde
>  
>  static int default_zonelist_order(void)
>  {
> -	/* dummy, just select node order. */
> -	return ZONELIST_ORDER_NODE;
> +	int nid, zone_type;
> +	unsigned long low_kmem_size,total_size;
> +	struct zone *z;
> +	int average_size;
> +	/*
> +         * ZONE_DMA and ZONE_DMA32 can be very small area in the sytem.
> +	 * If they are really small and used heavily, the system can fall
> +	 * into OOM very easily.
> +	 * This function detect ZONE_DMA/DMA32 size and confgigures zone order.
> +	 */
> +	/* Is there ZONE_NORMAL ? (ex. ppc has only DMA zone..) */
> +	low_kmem_size = 0;
> +	total_size = 0;
> +	for_each_online_node(nid) {
> +		for (zone_type = 0; zone_type < MAX_NR_ZONES; zone_type++) {
> +			z = &NODE_DATA(nid)->node_zones[zone_type];
> +			if (populated_zone(z)) {
> +				if (zone_type < ZONE_NORMAL)
> +					low_kmem_size += z->present_pages;
> +				total_size += z->present_pages;
> +			}
> +		}
> +	}
> +	if (!low_kmem_size ||  /* there are no DMA area. */
> +	    low_kmem_size > total_size/2) /* DMA/DMA32 is big. */
> +		return ZONELIST_ORDER_NODE;
> +	/*
> +	 * look into each node's config.
> +  	 * If there is a node whose DMA/DMA32 memory is very big area on
> + 	 * local memory, NODE_ORDER may be suitable.
> +         */
> +	average_size = total_size / (num_online_nodes() + 1);
> +	for_each_online_node(nid) {
> +		low_kmem_size = 0;
> +		total_size = 0;
> +		for (zone_type = 0; zone_type < MAX_NR_ZONES; zone_type++) {
> +			z = &NODE_DATA(nid)->node_zones[zone_type];
> +			if (populated_zone(z)) {
> +				if (zone_type < ZONE_NORMAL)
> +					low_kmem_size += z->present_pages;
> +				total_size += z->present_pages;
> +			}
> +		}
> +		if (low_kmem_size &&
> +		    total_size > average_size && /* ignore small node */
> +		    low_kmem_size > total_size * 70/100)
> +			return ZONELIST_ORDER_NODE;
> +	}
> +	return ZONELIST_ORDER_ZONE;
>  }
>  
> 
> 
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