[v2 PATCH 8/9] mm: vmscan: add page demotion counter

[Yang Shi]

Account the number of demoted pages into reclaim_state->nr_demoted.

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/internal.h                 | 1 +
 mm/vmscan.c                   | 7 +++++++
 mm/vmstat.c                   | 2 ++
 5 files changed, 13 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/internal.h b/mm/internal.h
index 8c424b5..8ba4853 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -156,6 +156,7 @@ struct scan_control {
                unsigned int immediate;
                unsigned int file_taken;
                unsigned int taken;
+               unsigned int demoted;
        } nr;
 };
 
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 50cde53..a52c8248 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1511,6 +1511,12 @@ static unsigned long shrink_page_list(struct list_head 
*page_list,
 
                nr_reclaimed += nr_succeeded;
 
+               stat->nr_demoted = nr_succeeded;
+               if (current_is_kswapd())
+                       __count_vm_events(PGDEMOTE_KSWAPD, stat->nr_demoted);
+               else
+                       __count_vm_events(PGDEMOTE_DIRECT, stat->nr_demoted);
+
                if (err) {
                        if (err == -ENOMEM)
                                set_bit(PGDAT_CONTENDED,
@@ -2019,6 +2025,7 @@ static int current_may_throttle(void)
        sc->nr.unqueued_dirty += stat.nr_unqueued_dirty;
        sc->nr.writeback += stat.nr_writeback;
        sc->nr.immediate += stat.nr_immediate;
+       sc->nr.demoted += stat.nr_demoted;
        sc->nr.taken += nr_taken;
        if (file)
                sc->nr.file_taken += nr_taken;
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 1a431dc..d1e4993 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