[PATCH 3/4] mm: workingset: add vmstat counter for shadow nodes

[Johannes Weiner]

Make it easier to catch bugs in the shadow node shrinker by adding a
counter for the shadow nodes in circulation.

Signed-off-by: Johannes Weiner <han...@cmpxchg.org>
---
 include/linux/mmzone.h |  1 +
 mm/vmstat.c            |  1 +
 mm/workingset.c        | 12 ++++++++++--
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 4179e67add3d..d82e80d82aa6 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -161,6 +161,7 @@ enum node_stat_item {
        NR_SLAB_UNRECLAIMABLE,
        NR_ISOLATED_ANON,       /* Temporary isolated pages from anon lru */
        NR_ISOLATED_FILE,       /* Temporary isolated pages from file lru */
+       WORKINGSET_NODES,
        WORKINGSET_REFAULT,
        WORKINGSET_ACTIVATE,
        WORKINGSET_RESTORE,
diff --git a/mm/vmstat.c b/mm/vmstat.c
index d08ed044759d..6038ce593ce3 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1143,6 +1143,7 @@ const char * const vmstat_text[] = {
        "nr_slab_unreclaimable",
        "nr_isolated_anon",
        "nr_isolated_file",
+       "workingset_nodes",
        "workingset_refault",
        "workingset_activate",
        "workingset_restore",
diff --git a/mm/workingset.c b/mm/workingset.c
index f564aaa6b71d..cfdf6adf7e7c 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -378,11 +378,17 @@ void workingset_update_node(struct xa_node *node)
         * as node->private_list is protected by the i_pages lock.
         */
        if (node->count && node->count == node->nr_values) {
-               if (list_empty(&node->private_list))
+               if (list_empty(&node->private_list)) {
                        list_lru_add(&shadow_nodes, &node->private_list);
+                       __inc_lruvec_page_state(virt_to_page(node),
+                                               WORKINGSET_NODES);
+               }
        } else {
-               if (!list_empty(&node->private_list))
+               if (!list_empty(&node->private_list)) {
                        list_lru_del(&shadow_nodes, &node->private_list);
+                       __dec_lruvec_page_state(virt_to_page(node),
+                                               WORKINGSET_NODES);
+               }
        }
 }
 
@@ -472,6 +478,8 @@ static enum lru_status shadow_lru_isolate(struct list_head 
*item,
        }
 
        list_lru_isolate(lru, item);
+       __dec_lruvec_page_state(virt_to_page(node), WORKINGSET_NODES);
+
        spin_unlock(lru_lock);
 
        /*
-- 
2.19.0