[PATCH] Thin out scan_control: remove nr_to_scan and priority

Make nr_to_scan and priority a parameter instead of putting it into scan
control.  This allows various small optimizations and IMHO makes the code
easier to read.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 25 insertions, 34 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index e21bab4deda6..f7c4f37c3b18 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -52,9 +52,6 @@ typedef enum {
 } pageout_t;
 
 struct scan_control {
-        /* Ask refill_inactive_zone, or shrink_cache to scan this many pages */
-        unsigned long nr_to_scan;
-
         /* Incremented by the number of inactive pages that were scanned */
         unsigned long nr_scanned;
 
@@ -63,9 +60,6 @@ struct scan_control {
 
         unsigned long nr_mapped;        /* From page_state */
 
-        /* Ask shrink_caches, or shrink_zone to scan at this priority */
-        unsigned int priority;
-
         /* This context's GFP mask */
         gfp_t gfp_mask;
 
@@ -1112,11 +1106,10 @@ static int isolate_lru_pages(int nr_to_scan, struct list_head *src,
 /*
  * shrink_cache() adds the number of pages reclaimed to sc->nr_reclaimed
  */
-static void shrink_cache(struct zone *zone, struct scan_control *sc)
+static void shrink_cache(int max_scan, struct zone *zone, struct scan_control *sc)
 {
         LIST_HEAD(page_list);
         struct pagevec pvec;
-        int max_scan = sc->nr_to_scan;
 
         pagevec_init(&pvec, 1);
 
@@ -1192,12 +1185,11 @@ done:
  * But we had to alter page->flags anyway.
  */
 static void
-refill_inactive_zone(struct zone *zone, struct scan_control *sc)
+refill_inactive_zone(int nr_pages, struct zone *zone, struct scan_control *sc)
 {
         int pgmoved;
         int pgdeactivate = 0;
         int pgscanned;
-        int nr_pages = sc->nr_to_scan;
         LIST_HEAD(l_hold);      /* The pages which were snipped off */
         LIST_HEAD(l_inactive);  /* Pages to go onto the inactive_list */
         LIST_HEAD(l_active);    /* Pages to go onto the active_list */
@@ -1332,10 +1324,11 @@ refill_inactive_zone(struct zone *zone, struct scan_control *sc)
  * This is a basic per-zone page freer.  Used by both kswapd and direct reclaim.
  */
 static void
-shrink_zone(struct zone *zone, struct scan_control *sc)
+shrink_zone(int priority, struct zone *zone, struct scan_control *sc)
 {
         unsigned long nr_active;
         unsigned long nr_inactive;
+        unsigned long nr_to_scan;
 
         atomic_inc(&zone->reclaim_in_progress);
 
@@ -1343,14 +1336,14 @@ shrink_zone(struct zone *zone, struct scan_control *sc)
          * Add one to `nr_to_scan' just to make sure that the kernel will
          * slowly sift through the active list.
          */
-        zone->nr_scan_active += (zone->nr_active >> sc->priority) + 1;
+        zone->nr_scan_active += (zone->nr_active >> priority) + 1;
         nr_active = zone->nr_scan_active;
         if (nr_active >= sc->swap_cluster_max)
                 zone->nr_scan_active = 0;
         else
                 nr_active = 0;
 
-        zone->nr_scan_inactive += (zone->nr_inactive >> sc->priority) + 1;
+        zone->nr_scan_inactive += (zone->nr_inactive >> priority) + 1;
         nr_inactive = zone->nr_scan_inactive;
         if (nr_inactive >= sc->swap_cluster_max)
                 zone->nr_scan_inactive = 0;
@@ -1359,17 +1352,17 @@ shrink_zone(struct zone *zone, struct scan_control *sc)
 
         while (nr_active || nr_inactive) {
                 if (nr_active) {
-                        sc->nr_to_scan = min(nr_active,
+                        nr_to_scan = min(nr_active,
                                         (unsigned long)sc->swap_cluster_max);
-                        nr_active -= sc->nr_to_scan;
-                        refill_inactive_zone(zone, sc);
+                        nr_active -= nr_to_scan;
+                        refill_inactive_zone(nr_to_scan, zone, sc);
                 }
 
                 if (nr_inactive) {
-                        sc->nr_to_scan = min(nr_inactive,
+                        nr_to_scan = min(nr_inactive,
                                         (unsigned long)sc->swap_cluster_max);
-                        nr_inactive -= sc->nr_to_scan;
-                        shrink_cache(zone, sc);
+                        nr_inactive -= nr_to_scan;
+                        shrink_cache(nr_to_scan, zone, sc);
                 }
         }
 
@@ -1395,7 +1388,7 @@ shrink_zone(struct zone *zone, struct scan_control *sc)
  * scan then give up on it.
  */
 static void
-shrink_caches(struct zone **zones, struct scan_control *sc)
+shrink_caches(int priority, struct zone **zones, struct scan_control *sc)
 {
         int i;
 
@@ -1408,14 +1401,14 @@ shrink_caches(struct zone **zones, struct scan_control *sc)
                 if (!cpuset_zone_allowed(zone, __GFP_HARDWALL))
                         continue;
 
-                zone->temp_priority = sc->priority;
-                if (zone->prev_priority > sc->priority)
-                        zone->prev_priority = sc->priority;
+                zone->temp_priority = priority;
+                if (zone->prev_priority > priority)
+                        zone->prev_priority = priority;
 
-                if (zone->all_unreclaimable && sc->priority != DEF_PRIORITY)
+                if (zone->all_unreclaimable && priority != DEF_PRIORITY)
                         continue;       /* Let kswapd poll it */
 
-                shrink_zone(zone, sc);
+                shrink_zone(priority, zone, sc);
         }
 }
  
@@ -1462,11 +1455,10 @@ int try_to_free_pages(struct zone **zones, gfp_t gfp_mask)
                 sc.nr_mapped = read_page_state(nr_mapped);
                 sc.nr_scanned = 0;
                 sc.nr_reclaimed = 0;
-                sc.priority = priority;
                 sc.swap_cluster_max = SWAP_CLUSTER_MAX;
                 if (!priority)
                         disable_swap_token();
-                shrink_caches(zones, &sc);
+                shrink_caches(priority, zones, &sc);
                 shrink_slab(sc.nr_scanned, gfp_mask, lru_pages);
                 if (reclaim_state) {
                         sc.nr_reclaimed += reclaim_state->reclaimed_slab;
@@ -1629,9 +1621,8 @@ scan:
                                 zone->prev_priority = priority;
                         sc.nr_scanned = 0;
                         sc.nr_reclaimed = 0;
-                        sc.priority = priority;
                         sc.swap_cluster_max = nr_pages? nr_pages : SWAP_CLUSTER_MAX;
-                        shrink_zone(zone, &sc);
+                        shrink_zone(priority, zone, &sc);
                         reclaim_state->reclaimed_slab = 0;
                         nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,
                                                 lru_pages);
@@ -1886,6 +1877,7 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
         struct scan_control sc;
         cpumask_t mask;
         int node_id;
+        int priority;
 
         if (time_before(jiffies,
                 zone->last_unsuccessful_zone_reclaim + zone_reclaim_interval))
@@ -1906,7 +1898,6 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
         sc.may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP);
         sc.nr_scanned = 0;
         sc.nr_reclaimed = 0;
-        sc.priority = ZONE_RECLAIM_PRIORITY + 1;
         sc.nr_mapped = read_page_state(nr_mapped);
         sc.gfp_mask = gfp_mask;
 
@@ -1932,11 +1923,11 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
          * Free memory by calling shrink zone with increasing priorities
          * until we have enough memory freed.
          */
+        priority = ZONE_RECLAIM_PRIORITY;
         do {
-                sc.priority--;
-                shrink_zone(zone, &sc);
-
-        } while (sc.nr_reclaimed < nr_pages && sc.priority > 0);
+                shrink_zone(priority, zone, &sc);
+                priority--;
+        } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
 
         if (sc.nr_reclaimed < nr_pages && (zone_reclaim_mode & RECLAIM_SLAB)) {
                 /*