mm: numa: Scan pages with elevated page_mapcount

Currently automatic NUMA balancing is unable to distinguish between false
shared versus private pages except by ignoring pages with an elevated
page_mapcount entirely. This avoids shared pages bouncing between the
nodes whose task is using them but that is ignored quite a lot of data.

This patch kicks away the training wheels in preparation for adding support
for identifying shared/private pages is now in place. The ordering is so
that the impact of the shared/private detection can be easily measured. Note
that the patch does not migrate shared, file-backed within vmas marked
VM_EXEC as these are generally shared library pages. Migrating such pages
is not beneficial as there is an expectation they are read-shared between
caches and iTLB and iCache pressure is generally low.

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>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1381141781-10992-28-git-send-email-mgorman@suse.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 2 insertions, 5 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 24bc9b848af6..3e3b4b8b6c41 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3577,7 +3577,7 @@ int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
         }
 
         /* Migrate to the requested node */
-        migrated = migrate_misplaced_page(page, target_nid);
+        migrated = migrate_misplaced_page(page, vma, target_nid);
         if (migrated)
                 page_nid = target_nid;
 
@@ -3642,16 +3642,13 @@ static int do_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
                 page = vm_normal_page(vma, addr, pteval);
                 if (unlikely(!page))
                         continue;
-                /* only check non-shared pages */
-                if (unlikely(page_mapcount(page) != 1))
-                        continue;
 
                 last_nid = page_nid_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, target_nid);
+                        migrated = migrate_misplaced_page(page, vma, target_nid);
                         if (migrated)
                                 page_nid = target_nid;
                 } else {