This is a [RFC] patch to support "no-fallback-to-DMA zonelist". against 2.6.22-rc6-mm1. any comments are welcome. -Kame In ia64 system, which are often used for servers, system configuration are very stable. Once fixed, it will be unchanged for years. And we can estimate "How much ZONE_DMA memory is enough for the system" in system development phase. (ZONE_DMA are used for 32bit devices like USB/Keyboard,CD-ROM,etc... and not used very often.) When we know ZONE_DMA can be small, we can reduce it by boot ops. But if we reduce ZONE_DMA memory by max_dma=XXX boot ops, the possibility of OOM in ZONE_DMA will increase under high memory pressure. This patch removes zonelist fallback among zone-types Normal-> DMA(32). By this, GFP_KERNEL memory request never use pages in zone below ZONE_NORMAL. There was a discussion that alloc_pfn_range(start,end), allocate some memory from [start,end), can be the silver bullet for problems around ZONE_DMA OOM in future. But I think this fix can be a method to handle OOM/ZONE_DMA for current kernel. (1) If "ZONELIST_ORDER_CONSERVATIVE" is strange, plz give me better name. (2) I'm now considering to move "zonelist" funcs to other (new) file. How do you think ? (3) This patch guarded DMA32, too. not necessary ? TODO: - add text to Documentation/. (not yet done.) Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> --- mm/page_alloc.c | 30 ++++++++++++++++++++++-------- 1 file changed, 22 insertions(+), 8 deletions(-) Index: linux-2.6.22-rc6-mm1/mm/page_alloc.c =================================================================== --- linux-2.6.22-rc6-mm1.orig/mm/page_alloc.c +++ linux-2.6.22-rc6-mm1/mm/page_alloc.c @@ -1982,19 +1982,23 @@ static int build_zonelists_node(pg_data_ * 0 = automatic detection of better ordering. * 1 = order by ([node] distance, -zonetype) * 2 = order by (-zonetype, [node] distance) - * + * 3 = diallow fallback from NORMAL -> DMA, order by zone. * If not NUMA, ZONELIST_ORDER_ZONE and ZONELIST_ORDER_NODE will create * the same zonelist. So only NUMA can configure this param. */ #define ZONELIST_ORDER_DEFAULT 0 #define ZONELIST_ORDER_NODE 1 #define ZONELIST_ORDER_ZONE 2 +#define ZONELIST_ORDER_CONSERVATIVE 3 /* zonelist order in the kernel. * set_zonelist_order() will set this to NODE or ZONE. + * Conservative is special settings for small DMA zone servers, + * This will be never selected automatically. */ static int current_zonelist_order = ZONELIST_ORDER_DEFAULT; -static char zonelist_order_name[3][8] = {"Default", "Node", "Zone"}; +static char zonelist_order_name[4][16] = {"Default", + "Node", "Zone", "Conservative"}; #ifdef CONFIG_NUMA @@ -2010,6 +2014,7 @@ char numa_zonelist_order[16] = "default" * = "[dD]efault - default, automatic configuration. * = "[nN]ode - order by node locality, then by zone within node * = "[zZ]one - order by zone, then by locality within zone + * = "[cC]onservative - Normal -> DMA fallback is disallowed. */ static int __parse_numa_zonelist_order(char *s) @@ -2020,6 +2025,8 @@ static int __parse_numa_zonelist_order(c user_zonelist_order = ZONELIST_ORDER_NODE; } else if (*s == 'z' || *s == 'Z') { user_zonelist_order = ZONELIST_ORDER_ZONE; + } else if (*s == 'c' || *s == 'C') { + user_zonelist_order = ZONELIST_ORDER_CONSERVATIVE; } else { printk(KERN_WARNING "Ignoring invalid numa_zonelist_order value: " @@ -2161,18 +2168,25 @@ static void build_zonelists_in_node_orde */ static int node_order[MAX_NUMNODES]; -static void build_zonelists_in_zone_order(pg_data_t *pgdat, int nr_nodes) +static void +build_zonelists_in_zone_order(pg_data_t *pgdat,int nr_nodes, int listorder) { enum zone_type i; int pos, j, node; - int zone_type; /* needs to be signed */ + int zone_type, low_zone; /* needs to be signed */ struct zone *z; struct zonelist *zonelist; for (i = 0; i < MAX_NR_ZONES; i++) { zonelist = pgdat->node_zonelists + i; pos = 0; - for (zone_type = i; zone_type >= 0; zone_type--) { + if ((listorder == ZONELIST_ORDER_CONSERVATIVE) && + (i >= ZONE_NORMAL)) + low_zone = ZONE_NORMAL; + else + low_zone = 0; + + for (zone_type = i; zone_type >= low_zone; zone_type--) { for (j = 0; j < nr_nodes; j++) { node = node_order[j]; z = &NODE_DATA(node)->node_zones[zone_type]; @@ -2298,10 +2312,10 @@ static void build_zonelists(pg_data_t *p node_order[j++] = node; /* remember order */ } - if (order == ZONELIST_ORDER_ZONE) { + if (order != ZONELIST_ORDER_NODE) /* calculate node order -- i.e., DMA last! */ - build_zonelists_in_zone_order(pgdat, j); - } + build_zonelists_in_zone_order(pgdat, j, order); + } /* Construct the zonelist performance cache - see further mmzone.h */ - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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