mm: restore zone->all_unreclaimable to independence word

commit e815af95 ("change all_unreclaimable zone member to flags") changed
all_unreclaimable member to bit flag.  But it had an undesireble side
effect.  free_one_page() is one of most hot path in linux kernel and
increasing atomic ops in it can reduce kernel performance a bit.

Thus, this patch revert such commit partially. at least
all_unreclaimable shouldn't share memory word with other zone flags.

[akpm@linux-foundation.org: fix patch interaction]
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Huang Shijie <shijie8@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 14 insertions, 23 deletions

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index a01a103341bd..bc209d8b7b5c 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -306,6 +306,7 @@ struct zone {
          * free areas of different sizes
          */
         spinlock_t              lock;
+        int                     all_unreclaimable; /* All pages pinned */
 #ifdef CONFIG_MEMORY_HOTPLUG
         /* see spanned/present_pages for more description */
         seqlock_t               span_seqlock;
@@ -417,7 +418,6 @@ struct zone {
 } ____cacheline_internodealigned_in_smp;
 
 typedef enum {
-        ZONE_ALL_UNRECLAIMABLE,         /* all pages pinned */
         ZONE_RECLAIM_LOCKED,            /* prevents concurrent reclaim */
         ZONE_OOM_LOCKED,                /* zone is in OOM killer zonelist */
 } zone_flags_t;
@@ -437,11 +437,6 @@ static inline void zone_clear_flag(struct zone *zone, zone_flags_t flag)
         clear_bit(flag, &zone->flags);
 }
 
-static inline int zone_is_all_unreclaimable(const struct zone *zone)
-{
-        return test_bit(ZONE_ALL_UNRECLAIMABLE, &zone->flags);
-}
-
 static inline int zone_is_reclaim_locked(const struct zone *zone)
 {
         return test_bit(ZONE_RECLAIM_LOCKED, &zone->flags);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 80bcee0c5034..0734bedabd9c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -530,7 +530,7 @@ static void free_pcppages_bulk(struct zone *zone, int count,
         int batch_free = 0;
 
         spin_lock(&zone->lock);
-        zone_clear_flag(zone, ZONE_ALL_UNRECLAIMABLE);
+        zone->all_unreclaimable = 0;
         zone->pages_scanned = 0;
 
         __mod_zone_page_state(zone, NR_FREE_PAGES, count);
@@ -568,7 +568,7 @@ static void free_one_page(struct zone *zone, struct page *page, int order,
                                 int migratetype)
 {
         spin_lock(&zone->lock);
-        zone_clear_flag(zone, ZONE_ALL_UNRECLAIMABLE);
+        zone->all_unreclaimable = 0;
         zone->pages_scanned = 0;
 
         __mod_zone_page_state(zone, NR_FREE_PAGES, 1 << order);
@@ -2262,7 +2262,7 @@ void show_free_areas(void)
                         K(zone_page_state(zone, NR_BOUNCE)),
                         K(zone_page_state(zone, NR_WRITEBACK_TEMP)),
                         zone->pages_scanned,
-                        (zone_is_all_unreclaimable(zone) ? "yes" : "no")
+                        (zone->all_unreclaimable ? "yes" : "no")
                         );
                 printk("lowmem_reserve[]:");
                 for (i = 0; i < MAX_NR_ZONES; i++)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index bc0f8db8340f..5cbf64dd79c1 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1699,8 +1699,7 @@ static void shrink_zones(int priority, struct zonelist *zonelist,
                                 continue;
                         note_zone_scanning_priority(zone, priority);
 
-                        if (zone_is_all_unreclaimable(zone) &&
-                                                priority != DEF_PRIORITY)
+                        if (zone->all_unreclaimable && priority != DEF_PRIORITY)
                                 continue;       /* Let kswapd poll it */
                         sc->all_unreclaimable = 0;
                 } else {
@@ -1927,7 +1926,7 @@ static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)
                 if (!populated_zone(zone))
                         continue;
 
-                if (zone_is_all_unreclaimable(zone))
+                if (zone->all_unreclaimable)
                         continue;
 
                 if (!zone_watermark_ok(zone, order, high_wmark_pages(zone),
@@ -2017,8 +2016,7 @@ loop_again:
                         if (!populated_zone(zone))
                                 continue;
 
-                        if (zone_is_all_unreclaimable(zone) &&
-                            priority != DEF_PRIORITY)
+                        if (zone->all_unreclaimable && priority != DEF_PRIORITY)
                                 continue;
 
                         /*
@@ -2061,8 +2059,7 @@ loop_again:
                         if (!populated_zone(zone))
                                 continue;
 
-                        if (zone_is_all_unreclaimable(zone) &&
-                                        priority != DEF_PRIORITY)
+                        if (zone->all_unreclaimable && priority != DEF_PRIORITY)
                                 continue;
 
                         temp_priority[i] = priority;
@@ -2089,12 +2086,11 @@ loop_again:
                                                 lru_pages);
                         sc.nr_reclaimed += reclaim_state->reclaimed_slab;
                         total_scanned += sc.nr_scanned;
-                        if (zone_is_all_unreclaimable(zone))
+                        if (zone->all_unreclaimable)
                                 continue;
-                        if (nr_slab == 0 && zone->pages_scanned >=
-                                        (zone_reclaimable_pages(zone) * 6))
-                                        zone_set_flag(zone,
-                                                      ZONE_ALL_UNRECLAIMABLE);
+                        if (nr_slab == 0 &&
+                            zone->pages_scanned >= (zone_reclaimable_pages(zone) * 6))
+                                zone->all_unreclaimable = 1;
                         /*
                          * If we've done a decent amount of scanning and
                          * the reclaim ratio is low, start doing writepage
@@ -2624,7 +2620,7 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
             zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
                 return ZONE_RECLAIM_FULL;
 
-        if (zone_is_all_unreclaimable(zone))
+        if (zone->all_unreclaimable)
                 return ZONE_RECLAIM_FULL;
 
         /*
diff --git a/mm/vmstat.c b/mm/vmstat.c
index fc5aa183bc45..7f760cbc73f3 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -763,7 +763,7 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
                    "\n  prev_priority:     %i"
                    "\n  start_pfn:         %lu"
                    "\n  inactive_ratio:    %u",
-                           zone_is_all_unreclaimable(zone),
+                   zone->all_unreclaimable,
                    zone->prev_priority,
                    zone->zone_start_pfn,
                    zone->inactive_ratio);