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