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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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