Demoted pages are counted into reclaim_state->nr_demoted instead of
nr_reclaimed since they are not reclaimed actually.  They are still in
memory, but just migrated to PMEM.

Add pgdemote_kswapd and pgdemote_direct VM counters showed in
/proc/vmstat.

Signed-off-by: Yang Shi <yang....@linux.alibaba.com>
---
 include/linux/vm_event_item.h |  2 ++
 include/linux/vmstat.h        |  1 +
 mm/vmscan.c                   | 14 ++++++++++++++
 mm/vmstat.c                   |  2 ++
 4 files changed, 19 insertions(+)

diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index 47a3441..499a3aa 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -32,6 +32,8 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
                PGREFILL,
                PGSTEAL_KSWAPD,
                PGSTEAL_DIRECT,
+               PGDEMOTE_KSWAPD,
+               PGDEMOTE_DIRECT,
                PGSCAN_KSWAPD,
                PGSCAN_DIRECT,
                PGSCAN_DIRECT_THROTTLE,
diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index 2db8d60..eb5d21c 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -29,6 +29,7 @@ struct reclaim_stat {
        unsigned nr_activate;
        unsigned nr_ref_keep;
        unsigned nr_unmap_fail;
+       unsigned nr_demoted;
 };
 
 #ifdef CONFIG_VM_EVENT_COUNTERS
diff --git a/mm/vmscan.c b/mm/vmscan.c
index bdcab6b..3c7ba7e 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1286,6 +1286,10 @@ static unsigned long shrink_page_list(struct list_head 
*page_list,
 
                        if (has_nonram_online()) {
                                list_add(&page->lru, &demote_pages);
+                               if (PageTransHuge(page))
+                                       stat->nr_demoted += HPAGE_PMD_NR;
+                               else
+                                       stat->nr_demoted++;
                                unlock_page(page);
                                continue;
                        }
@@ -1523,7 +1527,17 @@ static unsigned long shrink_page_list(struct list_head 
*page_list,
                        putback_movable_pages(&demote_pages);
 
                        list_splice(&ret_pages, &demote_pages);
+
+                       if (err > 0)
+                               stat->nr_demoted -= err;
+                       else
+                               stat->nr_demoted = 0;
                }
+
+               if (current_is_kswapd())
+                       __count_vm_events(PGDEMOTE_KSWAPD, stat->nr_demoted);
+               else
+                       __count_vm_events(PGDEMOTE_DIRECT, stat->nr_demoted);
        }
 
        mem_cgroup_uncharge_list(&free_pages);
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 36b56f8..0e863e7 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1192,6 +1192,8 @@ int fragmentation_index(struct zone *zone, unsigned int 
order)
        "pgrefill",
        "pgsteal_kswapd",
        "pgsteal_direct",
+       "pgdemote_kswapd",
+       "pgdemote_direct",
        "pgscan_kswapd",
        "pgscan_direct",
        "pgscan_direct_throttle",
-- 
1.8.3.1

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