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, 13 insertions, 2 deletions

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index becf92ca54f3..7ab4e32afe12 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1285,6 +1285,7 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
         int target_nid, last_cpupid = -1;
         bool page_locked;
         bool migrated = false;
+        int flags = 0;
 
         spin_lock(&mm->page_table_lock);
         if (unlikely(!pmd_same(pmd, *pmdp)))
@@ -1299,6 +1300,14 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
 
         /*
+         * 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 (!pmd_write(pmd))
+                flags |= TNF_NO_GROUP;
+
+        /*
          * Acquire the page lock to serialise THP migrations but avoid dropping
          * page_table_lock if at all possible
          */
@@ -1343,8 +1352,10 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
         spin_unlock(&mm->page_table_lock);
         migrated = migrate_misplaced_transhuge_page(mm, vma,
                                 pmdp, pmd, addr, page, target_nid);
-        if (migrated)
+        if (migrated) {
+                flags |= TNF_MIGRATED;
                 page_nid = target_nid;
+        }
 
         goto out;
 clear_pmdnuma:
@@ -1362,7 +1373,7 @@ out:
                 page_unlock_anon_vma_read(anon_vma);
 
         if (page_nid != -1)
-                task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, migrated);
+                task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags);
 
         return 0;
 }