mm, vmscan: release/reacquire lru_lock on pgdat change

With node-lru, the locking is based on the pgdat.  As Minchan pointed
out, there is an opportunity to reduce LRU lock release/acquire in
check_move_unevictable_pages by only changing lock on a pgdat change.

[mgorman@techsingularity.net: remove double initialisation]
  Link: http://lkml.kernel.org/r/20160719074835.GC10438@techsingularity.net
Link: http://lkml.kernel.org/r/1468853426-12858-3-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 11 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 4978ee9b5892..22aec2bcfeec 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3774,24 +3774,23 @@ int page_evictable(struct page *page)
 void check_move_unevictable_pages(struct page **pages, int nr_pages)
 {
         struct lruvec *lruvec;
-        struct zone *zone = NULL;
+        struct pglist_data *pgdat = NULL;
         int pgscanned = 0;
         int pgrescued = 0;
         int i;
 
         for (i = 0; i < nr_pages; i++) {
                 struct page *page = pages[i];
-                struct zone *pagezone;
+                struct pglist_data *pagepgdat = page_pgdat(page);
 
                 pgscanned++;
-                pagezone = page_zone(page);
-                if (pagezone != zone) {
-                        if (zone)
-                                spin_unlock_irq(zone_lru_lock(zone));
-                        zone = pagezone;
-                        spin_lock_irq(zone_lru_lock(zone));
+                if (pagepgdat != pgdat) {
+                        if (pgdat)
+                                spin_unlock_irq(&pgdat->lru_lock);
+                        pgdat = pagepgdat;
+                        spin_lock_irq(&pgdat->lru_lock);
                 }
-                lruvec = mem_cgroup_page_lruvec(page, zone->zone_pgdat);
+                lruvec = mem_cgroup_page_lruvec(page, pgdat);
 
                 if (!PageLRU(page) || !PageUnevictable(page))
                         continue;
@@ -3807,10 +3806,10 @@ void check_move_unevictable_pages(struct page **pages, int nr_pages)
                 }
         }
 
-        if (zone) {
+        if (pgdat) {
                 __count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
                 __count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
-                spin_unlock_irq(zone_lru_lock(zone));
+                spin_unlock_irq(&pgdat->lru_lock);
         }
 }
 #endif /* CONFIG_SHMEM */