Allow huge page allocations to use GFP_HIGH_MOVABLE

Huge pages are not movable so are not allocated from ZONE_MOVABLE.  However,
as ZONE_MOVABLE will always have pages that can be migrated or reclaimed, it
can be used to satisfy hugepage allocations even when the system has been
running a long time.  This allows an administrator to resize the hugepage pool
at runtime depending on the size of ZONE_MOVABLE.

This patch adds a new sysctl called hugepages_treat_as_movable.  When a
non-zero value is written to it, future allocations for the huge page pool
will use ZONE_MOVABLE.  Despite huge pages being non-movable, we do not
introduce additional external fragmentation of note as huge pages are always
the largest contiguous block we care about.

[akpm@linux-foundation.org: various fixes]
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 23 insertions, 5 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index acc0fb3..5898067 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -27,6 +27,9 @@ unsigned long max_huge_pages;
 static struct list_head hugepage_freelists[MAX_NUMNODES];
 static unsigned int nr_huge_pages_node[MAX_NUMNODES];
 static unsigned int free_huge_pages_node[MAX_NUMNODES];
+static gfp_t htlb_alloc_mask = GFP_HIGHUSER;
+unsigned long hugepages_treat_as_movable;
+
 /*
  * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
  */
@@ -68,12 +71,13 @@ static struct page *dequeue_huge_page(struct vm_area_struct *vma,
 {
 	int nid;
 	struct page *page = NULL;
-	struct zonelist *zonelist = huge_zonelist(vma, address);
+	struct zonelist *zonelist = huge_zonelist(vma, address,
+						htlb_alloc_mask);
 	struct zone **z;
 
 	for (z = zonelist->zones; *z; z++) {
 		nid = zone_to_nid(*z);
-		if (cpuset_zone_allowed_softwall(*z, GFP_HIGHUSER) &&
+		if (cpuset_zone_allowed_softwall(*z, htlb_alloc_mask) &&
 		    !list_empty(&hugepage_freelists[nid]))
 			break;
 	}
@@ -113,7 +117,7 @@ static int alloc_fresh_huge_page(void)
 	prev_nid = nid;
 	spin_unlock(&nid_lock);
 
-	page = alloc_pages_node(nid, GFP_HIGHUSER|__GFP_COMP|__GFP_NOWARN,
+	page = alloc_pages_node(nid, htlb_alloc_mask|__GFP_COMP|__GFP_NOWARN,
 					HUGETLB_PAGE_ORDER);
 	if (page) {
 		set_compound_page_dtor(page, free_huge_page);
@@ -263,6 +267,19 @@ int hugetlb_sysctl_handler(struct ctl_table *table, int write,
 	max_huge_pages = set_max_huge_pages(max_huge_pages);
 	return 0;
 }
+
+int hugetlb_treat_movable_handler(struct ctl_table *table, int write,
+			struct file *file, void __user *buffer,
+			size_t *length, loff_t *ppos)
+{
+	proc_dointvec(table, write, file, buffer, length, ppos);
+	if (hugepages_treat_as_movable)
+		htlb_alloc_mask = GFP_HIGHUSER_MOVABLE;
+	else
+		htlb_alloc_mask = GFP_HIGHUSER;
+	return 0;
+}
+
 #endif /* CONFIG_SYSCTL */
 
 int hugetlb_report_meminfo(char *buf)
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 4c0f999..9f4e9b9 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1203,7 +1203,8 @@ static inline unsigned interleave_nid(struct mempolicy *pol,
 
 #ifdef CONFIG_HUGETLBFS
 /* Return a zonelist suitable for a huge page allocation. */
-struct zonelist *huge_zonelist(struct vm_area_struct *vma, unsigned long addr)
+struct zonelist *huge_zonelist(struct vm_area_struct *vma, unsigned long addr,
+							gfp_t gfp_flags)
 {
 	struct mempolicy *pol = get_vma_policy(current, vma, addr);
 
@@ -1211,7 +1212,7 @@ struct zonelist *huge_zonelist(struct vm_area_struct *vma, unsigned long addr)
 		unsigned nid;
 
 		nid = interleave_nid(pol, vma, addr, HPAGE_SHIFT);
-		return NODE_DATA(nid)->node_zonelists + gfp_zone(GFP_HIGHUSER);
+		return NODE_DATA(nid)->node_zonelists + gfp_zone(gfp_flags);
 	}
 	return zonelist_policy(GFP_HIGHUSER, pol);
 }