mm: numa: Do not group on RO pages

And here's a little something to make sure not the whole world ends up
in a single group.

As while we don't migrate shared executable pages, we do scan/fault on
them. And since everybody links to libc, everybody ends up in the same
group.

Suggested-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1381141781-10992-47-git-send-email-mgorman@suse.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 26 insertions, 4 deletions

diff --git a/mm/memory.c b/mm/memory.c
index c57efa25cdbb..eba846bcf124 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3547,6 +3547,7 @@ int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
         int last_cpupid;
         int target_nid;
         bool migrated = false;
+        int flags = 0;
 
         /*
         * The "pte" at this point cannot be used safely without
@@ -3575,6 +3576,14 @@ int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
         }
         BUG_ON(is_zero_pfn(page_to_pfn(page)));
 
+        /*
+         * Avoid grouping on DSO/COW pages in specific and RO pages
+         * in general, RO pages shouldn't hurt as much anyway since
+         * they can be in shared cache state.
+         */
+        if (!pte_write(pte))
+                flags |= TNF_NO_GROUP;
+
         last_cpupid = page_cpupid_last(page);
         page_nid = page_to_nid(page);
         target_nid = numa_migrate_prep(page, vma, addr, page_nid);
@@ -3586,12 +3595,14 @@ int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
 
         /* Migrate to the requested node */
         migrated = migrate_misplaced_page(page, vma, target_nid);
-        if (migrated)
+        if (migrated) {
                 page_nid = target_nid;
+                flags |= TNF_MIGRATED;
+        }
 
 out:
         if (page_nid != -1)
-                task_numa_fault(last_cpupid, page_nid, 1, migrated);
+                task_numa_fault(last_cpupid, page_nid, 1, flags);
         return 0;
 }
 
@@ -3632,6 +3643,7 @@ static int do_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
                 int page_nid = -1;
                 int target_nid;
                 bool migrated = false;
+                int flags = 0;
 
                 if (!pte_present(pteval))
                         continue;
@@ -3651,20 +3663,30 @@ static int do_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
                 if (unlikely(!page))
                         continue;
 
+                /*
+                 * Avoid grouping on DSO/COW pages in specific and RO pages
+                 * in general, RO pages shouldn't hurt as much anyway since
+                 * they can be in shared cache state.
+                 */
+                if (!pte_write(pteval))
+                        flags |= TNF_NO_GROUP;
+
                 last_cpupid = page_cpupid_last(page);
                 page_nid = page_to_nid(page);
                 target_nid = numa_migrate_prep(page, vma, addr, page_nid);
                 pte_unmap_unlock(pte, ptl);
                 if (target_nid != -1) {
                         migrated = migrate_misplaced_page(page, vma, target_nid);
-                        if (migrated)
+                        if (migrated) {
                                 page_nid = target_nid;
+                                flags |= TNF_MIGRATED;
+                        }
                 } else {
                         put_page(page);
                 }
 
                 if (page_nid != -1)
-                        task_numa_fault(last_cpupid, page_nid, 1, migrated);
+                        task_numa_fault(last_cpupid, page_nid, 1, flags);
 
                 pte = pte_offset_map_lock(mm, pmdp, addr, &ptl);
         }