From: Yang Shi <[email protected]>

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

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

[ daveh:
   - __count_vm_events() a bit, and made them look at the THP
     size directly rather than getting data from migrate_pages()
]

Signed-off-by: Yang Shi <[email protected]>
Signed-off-by: Dave Hansen <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Huang Ying <[email protected]>
Cc: Dan Williams <[email protected]>
---

 b/include/linux/vm_event_item.h |    2 ++
 b/mm/migrate.c                  |   13 ++++++++++++-
 b/mm/vmscan.c                   |    1 +
 b/mm/vmstat.c                   |    2 ++
 4 files changed, 17 insertions(+), 1 deletion(-)

diff -puN include/linux/vm_event_item.h~mm-vmscan-add-page-demotion-counter 
include/linux/vm_event_item.h
--- a/include/linux/vm_event_item.h~mm-vmscan-add-page-demotion-counter 
2020-06-29 16:34:40.332312601 -0700
+++ b/include/linux/vm_event_item.h     2020-06-29 16:34:40.342312601 -0700
@@ -32,6 +32,8 @@ enum vm_event_item { PGPGIN, PGPGOUT, PS
                PGREFILL,
                PGSTEAL_KSWAPD,
                PGSTEAL_DIRECT,
+               PGDEMOTE_KSWAPD,
+               PGDEMOTE_DIRECT,
                PGSCAN_KSWAPD,
                PGSCAN_DIRECT,
                PGSCAN_DIRECT_THROTTLE,
diff -puN mm/migrate.c~mm-vmscan-add-page-demotion-counter mm/migrate.c
--- a/mm/migrate.c~mm-vmscan-add-page-demotion-counter  2020-06-29 
16:34:40.334312601 -0700
+++ b/mm/migrate.c      2020-06-29 16:34:40.343312601 -0700
@@ -1187,6 +1187,7 @@ static struct page *alloc_demote_node_pa
 int migrate_demote_mapping(struct page *page)
 {
        int next_nid = next_demotion_node(page_to_nid(page));
+       int ret;
 
        VM_BUG_ON_PAGE(!PageLocked(page), page);
        VM_BUG_ON_PAGE(PageHuge(page), page);
@@ -1198,8 +1199,18 @@ int migrate_demote_mapping(struct page *
                return -ENOMEM;
 
        /* MIGRATE_ASYNC is the most light weight and never blocks.*/
-       return __unmap_and_move(alloc_demote_node_page, NULL, next_nid,
+       ret = __unmap_and_move(alloc_demote_node_page, NULL, next_nid,
                                page, MIGRATE_ASYNC, MR_DEMOTION);
+
+       if (ret == MIGRATEPAGE_SUCCESS) {
+               int nr_demoted = hpage_nr_pages(page);
+               if (current_is_kswapd())
+                       __count_vm_events(PGDEMOTE_KSWAPD, nr_demoted);
+               else
+                       __count_vm_events(PGDEMOTE_DIRECT, nr_demoted);
+       }
+
+       return ret;
 }
 
 
diff -puN mm/vmscan.c~mm-vmscan-add-page-demotion-counter mm/vmscan.c
--- a/mm/vmscan.c~mm-vmscan-add-page-demotion-counter   2020-06-29 
16:34:40.336312601 -0700
+++ b/mm/vmscan.c       2020-06-29 16:34:40.344312601 -0700
@@ -140,6 +140,7 @@ struct scan_control {
                unsigned int immediate;
                unsigned int file_taken;
                unsigned int taken;
+               unsigned int demoted;
        } nr;
 
        /* for recording the reclaimed slab by now */
diff -puN mm/vmstat.c~mm-vmscan-add-page-demotion-counter mm/vmstat.c
--- a/mm/vmstat.c~mm-vmscan-add-page-demotion-counter   2020-06-29 
16:34:40.339312601 -0700
+++ b/mm/vmstat.c       2020-06-29 16:34:40.345312601 -0700
@@ -1198,6 +1198,8 @@ const char * const vmstat_text[] = {
        "pgrefill",
        "pgsteal_kswapd",
        "pgsteal_direct",
+       "pgdemote_kswapd",
+       "pgdemote_direct",
        "pgscan_kswapd",
        "pgscan_direct",
        "pgscan_direct_throttle",
_

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