vmscan: separate sc.swap_cluster_max and sc.nr_max_reclaim

Currently, sc.scap_cluster_max has double meanings.

 1) reclaim batch size as isolate_lru_pages()'s argument
 2) reclaim baling out thresolds

The two meanings pretty unrelated. Thus, Let's separate it.
this patch doesn't change any behavior.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 19 insertions, 6 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index cb69f717799f..7b0d5c784c7e 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -55,6 +55,9 @@ struct scan_control {
         /* Number of pages freed so far during a call to shrink_zones() */
         unsigned long nr_reclaimed;
 
+        /* How many pages shrink_list() should reclaim */
+        unsigned long nr_to_reclaim;
+
         /* This context's GFP mask */
         gfp_t gfp_mask;
 
@@ -1595,6 +1598,7 @@ static void shrink_zone(int priority, struct zone *zone,
         enum lru_list l;
         unsigned long nr_reclaimed = sc->nr_reclaimed;
         unsigned long swap_cluster_max = sc->swap_cluster_max;
+        unsigned long nr_to_reclaim = sc->nr_to_reclaim;
         struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
         int noswap = 0;
 
@@ -1639,8 +1643,7 @@ static void shrink_zone(int priority, struct zone *zone,
                  * with multiple processes reclaiming pages, the total
                  * freeing target can get unreasonably large.
                  */
-                if (nr_reclaimed > swap_cluster_max &&
-                        priority < DEF_PRIORITY && !current_is_kswapd())
+                if (nr_reclaimed > nr_to_reclaim && priority < DEF_PRIORITY)
                         break;
         }
 
@@ -1738,6 +1741,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
         struct zoneref *z;
         struct zone *zone;
         enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask);
+        unsigned long writeback_threshold;
 
         delayacct_freepages_start();
 
@@ -1773,7 +1777,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
                         }
                 }
                 total_scanned += sc->nr_scanned;
-                if (sc->nr_reclaimed >= sc->swap_cluster_max) {
+                if (sc->nr_reclaimed >= sc->nr_to_reclaim) {
                         ret = sc->nr_reclaimed;
                         goto out;
                 }
@@ -1785,8 +1789,8 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
                  * that's undesirable in laptop mode, where we *want* lumpy
                  * writeout.  So in laptop mode, write out the whole world.
                  */
-                if (total_scanned > sc->swap_cluster_max +
-                                        sc->swap_cluster_max / 2) {
+                writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
+                if (total_scanned > writeback_threshold) {
                         wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
                         sc->may_writepage = 1;
                 }
@@ -1832,6 +1836,7 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
                 .gfp_mask = gfp_mask,
                 .may_writepage = !laptop_mode,
                 .swap_cluster_max = SWAP_CLUSTER_MAX,
+                .nr_to_reclaim = SWAP_CLUSTER_MAX,
                 .may_unmap = 1,
                 .may_swap = 1,
                 .swappiness = vm_swappiness,
@@ -1890,6 +1895,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
                 .may_unmap = 1,
                 .may_swap = !noswap,
                 .swap_cluster_max = SWAP_CLUSTER_MAX,
+                .nr_to_reclaim = SWAP_CLUSTER_MAX,
                 .swappiness = swappiness,
                 .order = 0,
                 .mem_cgroup = mem_cont,
@@ -1961,6 +1967,11 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
                 .may_unmap = 1,
                 .may_swap = 1,
                 .swap_cluster_max = SWAP_CLUSTER_MAX,
+                /*
+                 * kswapd doesn't want to be bailed out while reclaim. because
+                 * we want to put equal scanning pressure on each zone.
+                 */
+                .nr_to_reclaim = ULONG_MAX,
                 .swappiness = vm_swappiness,
                 .order = order,
                 .mem_cgroup = NULL,
@@ -2630,7 +2641,9 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
                 .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
                 .may_swap = 1,
                 .swap_cluster_max = max_t(unsigned long, nr_pages,
-                                        SWAP_CLUSTER_MAX),
+                                       SWAP_CLUSTER_MAX),
+                .nr_to_reclaim = max_t(unsigned long, nr_pages,
+                                       SWAP_CLUSTER_MAX),
                 .gfp_mask = gfp_mask,
                 .swappiness = vm_swappiness,
                 .order = order,