From: Dan Williams <dan.j.williams@intel.com>
Date: Tue, 13 Dec 2016 00:43:12 +0000 (-0800)
Subject: mm: disable numa migration faults for dax vmas
X-Git-Tag: v4.14-rc1~1942^2~71
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=c1ef8e2c0235bffe4b0505c3325bb8a6af954021;p=platform%2Fkernel%2Flinux-rpi3.git

mm: disable numa migration faults for dax vmas

Mark dax vmas as not migratable to exclude them from task_numa_work().
This is especially relevant for device-dax which wants to ensure
predictable access latency and not incur periodic faults.

[akpm@linux-foundation.org: add comment]
Link: http://lkml.kernel.org/r/147892450132.22062.16875659431109209179.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reported-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
index 5e5b296..5f4d828 100644
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -7,6 +7,7 @@
 
 
 #include <linux/mmzone.h>
+#include <linux/dax.h>
 #include <linux/slab.h>
 #include <linux/rbtree.h>
 #include <linux/spinlock.h>
@@ -177,6 +178,13 @@ static inline bool vma_migratable(struct vm_area_struct *vma)
 	if (vma->vm_flags & (VM_IO | VM_PFNMAP))
 		return false;
 
+	/*
+	 * DAX device mappings require predictable access latency, so avoid
+	 * incurring periodic faults.
+	 */
+	if (vma_is_dax(vma))
+		return false;
+
 #ifndef CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION
 	if (vma->vm_flags & VM_HUGETLB)
 		return false;