IMPORTANT NOTE: It's unclear how safe it is to declare nodemask_t on the
stack, when nodemask_t can be relatively large in huge NUMA systems.
Upcoming patches will try to limit this.
The primary purpose of this patch is to clear up which interfaces should
be used for page allocation.
There are several attributes in page allocation after the obvious gfp
and order:
1. node mask: set of nodes to try to allocate from, fail if unavailable
2. preferred nid: a preferred node to try to allocate from, falling back
to node mask if unavailable
3. (soon) preferred mask: like preferred nid, but multiple nodes.
Here's a summary of the existing interfaces, and which they cover
*alloc_pages: ()
*alloc_pages_node: (2)
__alloc_pages_nodemask: (1,2,3)
I am instead proposing instead the following interfaces as a reasonable
set. Generally node binding isn't used by kernel code, it's only used
for mempolicy. On the other hand, the kernel does have preferred nodes
(today it's only one), and that is why those interfaces exist while an
interface to specify binding does not.
alloc_pages: () I don't care, give me pages.
alloc_pages_node: (2) I want pages from this particular node first
alloc_pages_nodes: (3) I want pages from *these* nodes first
__alloc_pages_nodemask: (1,2,3) I'm picky about my pages
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Signed-off-by: Ben Widawsky <ben.widawsky@xxxxxxxxx>
---
include/linux/gfp.h | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 67a0774e080b..9ab5c07579bd 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -504,9 +504,10 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, int preferred_nid,
nodemask_t *nodemask);
static inline struct page *
-__alloc_pages(gfp_t gfp_mask, unsigned int order, int preferred_nid)
+__alloc_pages_nodes(nodemask_t *nodes, gfp_t gfp_mask, unsigned int order)
{
- return __alloc_pages_nodemask(gfp_mask, order, preferred_nid, NULL);
+ return __alloc_pages_nodemask(gfp_mask, order, first_node(*nodes),
+ NULL);
}
/*
@@ -516,10 +517,12 @@ __alloc_pages(gfp_t gfp_mask, unsigned int order, int preferred_nid)
static inline struct page *
__alloc_pages_node(int nid, gfp_t gfp_mask, unsigned int order)
{
+ nodemask_t tmp;
VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES);
VM_WARN_ON((gfp_mask & __GFP_THISNODE) && !node_online(nid));
- return __alloc_pages(gfp_mask, order, nid);
+ tmp = nodemask_of_node(nid);
+ return __alloc_pages_nodes(&tmp, gfp_mask, order);
}
/*
--
2.27.0
