[RFC V2 11/12] mm: Tag VMA with VM_CDM flag during page fault

[Anshuman Khandual <khandual@linux.vnet.ibm.com>]

Mark the corresponding VMA with VM_CDM flag if the allocated page happens
to be from a CDM node. This can be expensive from performance stand point.
There are multiple checks to avoid an expensive page_to_nid lookup but it
can be optimized further.

Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
---
 mm/mempolicy.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 6089c711..78e095b 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -174,6 +174,29 @@ static void mpol_relative_nodemask(nodemask_t *ret, const nodemask_t *orig,
 	nodes_onto(*ret, tmp, *rel);
 }
 
+#ifdef CONFIG_COHERENT_DEVICE
+static void mark_vma_cdm(nodemask_t *nmask,
+		struct page *page, struct vm_area_struct *vma)
+{
+	if (!page)
+		return;
+
+	if (vma->vm_flags & VM_CDM)
+		return;
+
+	if (nmask && !nodemask_has_cdm(*nmask))
+		return;
+
+	if (is_cdm_node(page_to_nid(page)))
+		vma->vm_flags |= VM_CDM;
+}
+#else
+static void mark_vma_cdm(nodemask_t *nmask,
+		struct page *page, struct vm_area_struct *vma)
+{
+}
+#endif
+
 static int mpol_new_interleave(struct mempolicy *pol, const nodemask_t *nodes)
 {
 	if (nodes_empty(*nodes))
@@ -2039,6 +2062,7 @@ alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
 	nmask = policy_nodemask(gfp, pol);
 	zl = policy_zonelist(gfp, pol, node);
 	page = __alloc_pages_nodemask(gfp, order, zl, nmask);
+	mark_vma_cdm(nmask, page, vma);
 	mpol_cond_put(pol);
 out:
 	if (unlikely(!page && read_mems_allowed_retry(cpuset_mems_cookie)))
-- 
2.9.3

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