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SubjectRe: [PATCH 6/6] Use one zonelist that is filtered by nodemask
On (09/11/07 07:45), Christoph Lameter didst pronounce:
> On Fri, 9 Nov 2007, Mel Gorman wrote:
>
> > struct page * fastcall
> > __alloc_pages(gfp_t gfp_mask, unsigned int order,
> > struct zonelist *zonelist)
> > {
> > + /*
> > + * Use a temporary nodemask for __GFP_THISNODE allocations. If the
> > + * cost of allocating on the stack or the stack usage becomes
> > + * noticable, allocate the nodemasks per node at boot or compile time
> > + */
> > + if (unlikely(gfp_mask & __GFP_THISNODE)) {
> > + nodemask_t nodemask;
>
> Hmmm.. This places a potentially big structure on the stack. nodemask can
> contain up to 1024 bits which means 128 bytes. Maybe keep an array of
> gfp_thisnode nodemasks (node_nodemask?) and use node_nodemask[nid]?

Went back and revisited this. Allocating them at boot-time is below but
essentially it is a silly and it makes sense to just have two zonelists
where one of them is for __GFP_THISNODE. Implementation wise, this involves
dropping the last patch in the set and the overall result is still a reduction
in the number of zonelists.

diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.24-rc2-mm1-040_use_one_zonelist/include/linux/gfp.h linux-2.6.24-rc2-mm1-045_use_static_nodemask/include/linux/gfp.h
--- linux-2.6.24-rc2-mm1-040_use_one_zonelist/include/linux/gfp.h 2007-11-19 19:27:15.000000000 +0000
+++ linux-2.6.24-rc2-mm1-045_use_static_nodemask/include/linux/gfp.h 2007-11-19 19:28:55.000000000 +0000
@@ -175,7 +175,6 @@ FASTCALL(__alloc_pages(gfp_t, unsigned i
extern struct page *
FASTCALL(__alloc_pages_nodemask(gfp_t, unsigned int,
struct zonelist *, nodemask_t *nodemask));
-extern nodemask_t *nodemask_thisnode(int nid, nodemask_t *nodemask);

static inline struct page *alloc_pages_node(int nid, gfp_t gfp_mask,
unsigned int order)
@@ -187,13 +186,10 @@ static inline struct page *alloc_pages_n
if (nid < 0)
nid = numa_node_id();

- /* Use a temporary nodemask for __GFP_THISNODE allocations */
if (unlikely(gfp_mask & __GFP_THISNODE)) {
- nodemask_t nodemask;
-
return __alloc_pages_nodemask(gfp_mask, order,
node_zonelist(nid),
- nodemask_thisnode(nid, &nodemask));
+ NODE_DATA(nid)->nodemask_thisnode);
}

return __alloc_pages(gfp_mask, order, node_zonelist(nid));
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.24-rc2-mm1-040_use_one_zonelist/include/linux/mmzone.h linux-2.6.24-rc2-mm1-045_use_static_nodemask/include/linux/mmzone.h
--- linux-2.6.24-rc2-mm1-040_use_one_zonelist/include/linux/mmzone.h 2007-11-19 19:27:15.000000000 +0000
+++ linux-2.6.24-rc2-mm1-045_use_static_nodemask/include/linux/mmzone.h 2007-11-19 19:28:55.000000000 +0000
@@ -519,6 +519,9 @@ typedef struct pglist_data {
struct zone node_zones[MAX_NR_ZONES];
struct zonelist node_zonelist;
int nr_zones;
+
+ /* nodemask suitable for __GFP_THISNODE */
+ nodemask_t *nodemask_thisnode;
#ifdef CONFIG_FLAT_NODE_MEM_MAP
struct page *node_mem_map;
#endif
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.24-rc2-mm1-040_use_one_zonelist/mm/page_alloc.c linux-2.6.24-rc2-mm1-045_use_static_nodemask/mm/page_alloc.c
--- linux-2.6.24-rc2-mm1-040_use_one_zonelist/mm/page_alloc.c 2007-11-19 19:27:15.000000000 +0000
+++ linux-2.6.24-rc2-mm1-045_use_static_nodemask/mm/page_alloc.c 2007-11-19 19:28:55.000000000 +0000
@@ -1695,28 +1695,36 @@ got_pg:
}

/* Creates a nodemask suitable for GFP_THISNODE allocations */
-nodemask_t *nodemask_thisnode(int nid, nodemask_t *nodemask)
+static inline void alloc_node_nodemask_thisnode(pg_data_t *pgdat)
{
- nodes_clear(*nodemask);
- node_set(nid, *nodemask);
+ nodemask_t *nodemask_thisnode;

- return nodemask;
+ /* Only a machine with multiple nodes needs the nodemask */
+ if (!NUMA_BUILD || num_online_nodes() == 1)
+ return;
+
+ /* Allocate the nodemask. Serious if it fails, but not world ending */
+ nodemask_thisnode = alloc_bootmem_node(pgdat, sizeof(nodemask_t));
+ if (!nodemask_thisnode) {
+ printk(KERN_WARNING
+ "thisnode nodemask allocation failed."
+ "There may be sub-optimal NUMA placement.\n");
+ return;
+ }
+
+ /* Initialise the nodemask to only cover the current node */
+ nodes_clear(*nodemask_thisnode);
+ node_set(pgdat->node_id, *nodemask_thisnode);
+ pgdat->nodemask_thisnode = nodemask_thisnode;
}

struct page * fastcall
__alloc_pages(gfp_t gfp_mask, unsigned int order,
struct zonelist *zonelist)
{
- /*
- * Use a temporary nodemask for __GFP_THISNODE allocations. If the
- * cost of allocating on the stack or the stack usage becomes
- * noticable, allocate the nodemasks per node at boot or compile time
- */
if (unlikely(gfp_mask & __GFP_THISNODE)) {
- nodemask_t nodemask;
-
- return __alloc_pages_internal(gfp_mask, order,
- zonelist, nodemask_thisnode(numa_node_id(), &nodemask));
+ return __alloc_pages_internal(gfp_mask, order, zonelist,
+ NODE_DATA(numa_node_id())->nodemask_thisnode);
}

return __alloc_pages_internal(gfp_mask, order, zonelist, NULL);
@@ -3501,6 +3509,7 @@ void __meminit free_area_init_node(int n
calculate_node_totalpages(pgdat, zones_size, zholes_size);

alloc_node_mem_map(pgdat);
+ alloc_node_nodemask_thisnode(pgdat);

free_area_init_core(pgdat, zones_size, zholes_size);
}
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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