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 <[EMAIL PROTECTED]>
---
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 */
-
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