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>

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 4978ee9b5892eb93e7069ae4aa09aaefaa888e2d..22aec2bcfeec6ac305da6d7f28f59acc5ef08191 100644 (file)
--- 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 */