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>

4 files changed, 47 insertions, 10 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index b0b343b1ba64..ff543851a18a 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1450,13 +1450,16 @@ struct task_struct {
 /* Future-safe accessor for struct task_struct's cpus_allowed. */
 #define tsk_cpus_allowed(tsk) (&(tsk)->cpus_allowed)
 
+#define TNF_MIGRATED    0x01
+#define TNF_NO_GROUP    0x02
+
 #ifdef CONFIG_NUMA_BALANCING
-extern void task_numa_fault(int last_node, int node, int pages, bool migrated);
+extern void task_numa_fault(int last_node, int node, int pages, int flags);
 extern pid_t task_numa_group_id(struct task_struct *p);
 extern void set_numabalancing_state(bool enabled);
 #else
 static inline void task_numa_fault(int last_node, int node, int pages,
-                                   bool migrated)
+                                   int flags)
 {
 }
 static inline pid_t task_numa_group_id(struct task_struct *p)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 5bd309c035c7..35661b8afb4e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1361,9 +1361,10 @@ void task_numa_free(struct task_struct *p)
 /*
  * Got a PROT_NONE fault for a page on @node.
  */
-void task_numa_fault(int last_cpupid, int node, int pages, bool migrated)
+void task_numa_fault(int last_cpupid, int node, int pages, int flags)
 {
         struct task_struct *p = current;
+        bool migrated = flags & TNF_MIGRATED;
         int priv;
 
         if (!numabalancing_enabled)
@@ -1394,7 +1395,7 @@ void task_numa_fault(int last_cpupid, int node, int pages, bool migrated)
                 priv = 1;
         } else {
                 priv = cpupid_match_pid(p, last_cpupid);
-                if (!priv)
+                if (!priv && !(flags & TNF_NO_GROUP))
                         task_numa_group(p, last_cpupid);
         }
 
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;
 }
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);
         }