vmscan: simplify shrink_inactive_list()

Now, max_scan of shrink_inactive_list() is always passed less than
SWAP_CLUSTER_MAX.  then, we can remove scanning pages loop in it.  This
patch also help stack diet.

detail
 - remove "while (nr_scanned < max_scan)" loop
 - remove nr_freed (now, we use nr_reclaimed directly)
 - remove nr_scan (now, we use nr_scanned directly)
 - rename max_scan to nr_to_scan
 - pass nr_to_scan into isolate_pages() directly instead
   using SWAP_CLUSTER_MAX

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michael Rubin <mrubin@google.com>
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 594eba8..8522327 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1136,15 +1136,21 @@ static int too_many_isolated(struct zone *zone, int file,
  * shrink_inactive_list() is a helper for shrink_zone().  It returns the number
  * of reclaimed pages
  */
-static unsigned long shrink_inactive_list(unsigned long max_scan,
+static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
                        struct zone *zone, struct scan_control *sc,
                        int priority, int file)
 {
        LIST_HEAD(page_list);
        struct pagevec pvec;
-       unsigned long nr_scanned = 0;
+       unsigned long nr_scanned;
        unsigned long nr_reclaimed = 0;
        struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
+       struct page *page;
+       unsigned long nr_taken;
+       unsigned long nr_active;
+       unsigned int count[NR_LRU_LISTS] = { 0, };
+       unsigned long nr_anon;
+       unsigned long nr_file;
 
        while (unlikely(too_many_isolated(zone, file, sc))) {
                congestion_wait(BLK_RW_ASYNC, HZ/10);
@@ -1159,129 +1165,115 @@ static unsigned long shrink_inactive_list(unsigned long max_scan,
 
        lru_add_drain();
        spin_lock_irq(&zone->lru_lock);
-       do {
-               struct page *page;
-               unsigned long nr_taken;
-               unsigned long nr_scan;
-               unsigned long nr_freed;
-               unsigned long nr_active;
-               unsigned int count[NR_LRU_LISTS] = { 0, };
-               int mode = sc->lumpy_reclaim_mode ? ISOLATE_BOTH : ISOLATE_INACTIVE;
-               unsigned long nr_anon;
-               unsigned long nr_file;
 
-               if (scanning_global_lru(sc)) {
-                       nr_taken = isolate_pages_global(SWAP_CLUSTER_MAX,
-                                                       &page_list, &nr_scan,
-                                                       sc->order, mode,
-                                                       zone, 0, file);
-                       zone->pages_scanned += nr_scan;
-                       if (current_is_kswapd())
-                               __count_zone_vm_events(PGSCAN_KSWAPD, zone,
-                                                      nr_scan);
-                       else
-                               __count_zone_vm_events(PGSCAN_DIRECT, zone,
-                                                      nr_scan);
-               } else {
-                       nr_taken = mem_cgroup_isolate_pages(SWAP_CLUSTER_MAX,
-                                                       &page_list, &nr_scan,
-                                                       sc->order, mode,
-                                                       zone, sc->mem_cgroup,
-                                                       0, file);
-                       /*
-                        * mem_cgroup_isolate_pages() keeps track of
-                        * scanned pages on its own.
-                        */
-               }
+       if (scanning_global_lru(sc)) {
+               nr_taken = isolate_pages_global(nr_to_scan,
+                       &page_list, &nr_scanned, sc->order,
+                       sc->lumpy_reclaim_mode ?
+                               ISOLATE_BOTH : ISOLATE_INACTIVE,
+                       zone, 0, file);
+               zone->pages_scanned += nr_scanned;
+               if (current_is_kswapd())
+                       __count_zone_vm_events(PGSCAN_KSWAPD, zone,
+                                              nr_scanned);
+               else
+                       __count_zone_vm_events(PGSCAN_DIRECT, zone,
+                                              nr_scanned);
+       } else {
+               nr_taken = mem_cgroup_isolate_pages(nr_to_scan,
+                       &page_list, &nr_scanned, sc->order,
+                       sc->lumpy_reclaim_mode ?
+                               ISOLATE_BOTH : ISOLATE_INACTIVE,
+                       zone, sc->mem_cgroup,
+                       0, file);
+               /*
+                * mem_cgroup_isolate_pages() keeps track of
+                * scanned pages on its own.
+                */
+       }
 
-               if (nr_taken == 0)
-                       goto done;
+       if (nr_taken == 0)
+               goto done;
 
-               nr_active = clear_active_flags(&page_list, count);
-               __count_vm_events(PGDEACTIVATE, nr_active);
+       nr_active = clear_active_flags(&page_list, count);
+       __count_vm_events(PGDEACTIVATE, nr_active);
 
-               __mod_zone_page_state(zone, NR_ACTIVE_FILE,
-                                               -count[LRU_ACTIVE_FILE]);
-               __mod_zone_page_state(zone, NR_INACTIVE_FILE,
-                                               -count[LRU_INACTIVE_FILE]);
-               __mod_zone_page_state(zone, NR_ACTIVE_ANON,
-                                               -count[LRU_ACTIVE_ANON]);
-               __mod_zone_page_state(zone, NR_INACTIVE_ANON,
-                                               -count[LRU_INACTIVE_ANON]);
+       __mod_zone_page_state(zone, NR_ACTIVE_FILE,
+                                       -count[LRU_ACTIVE_FILE]);
+       __mod_zone_page_state(zone, NR_INACTIVE_FILE,
+                                       -count[LRU_INACTIVE_FILE]);
+       __mod_zone_page_state(zone, NR_ACTIVE_ANON,
+                                       -count[LRU_ACTIVE_ANON]);
+       __mod_zone_page_state(zone, NR_INACTIVE_ANON,
+                                       -count[LRU_INACTIVE_ANON]);
 
-               nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
-               nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
-               __mod_zone_page_state(zone, NR_ISOLATED_ANON, nr_anon);
-               __mod_zone_page_state(zone, NR_ISOLATED_FILE, nr_file);
+       nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
+       nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
+       __mod_zone_page_state(zone, NR_ISOLATED_ANON, nr_anon);
+       __mod_zone_page_state(zone, NR_ISOLATED_FILE, nr_file);
 
-               reclaim_stat->recent_scanned[0] += nr_anon;
-               reclaim_stat->recent_scanned[1] += nr_file;
+       reclaim_stat->recent_scanned[0] += nr_anon;
+       reclaim_stat->recent_scanned[1] += nr_file;
 
-               spin_unlock_irq(&zone->lru_lock);
+       spin_unlock_irq(&zone->lru_lock);
 
-               nr_scanned += nr_scan;
-               nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
+       nr_reclaimed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
+
+       /*
+        * If we are direct reclaiming for contiguous pages and we do
+        * not reclaim everything in the list, try again and wait
+        * for IO to complete. This will stall high-order allocations
+        * but that should be acceptable to the caller
+        */
+       if (nr_reclaimed < nr_taken && !current_is_kswapd() &&
+                       sc->lumpy_reclaim_mode) {
+               congestion_wait(BLK_RW_ASYNC, HZ/10);
 
                /*
-                * If we are direct reclaiming for contiguous pages and we do
-                * not reclaim everything in the list, try again and wait
-                * for IO to complete. This will stall high-order allocations
-                * but that should be acceptable to the caller
+                * The attempt at page out may have made some
+                * of the pages active, mark them inactive again.
                 */
-               if (nr_freed < nr_taken && !current_is_kswapd() &&
-                   sc->lumpy_reclaim_mode) {
-                       congestion_wait(BLK_RW_ASYNC, HZ/10);
-
-                       /*
-                        * The attempt at page out may have made some
-                        * of the pages active, mark them inactive again.
-                        */
-                       nr_active = clear_active_flags(&page_list, count);
-                       count_vm_events(PGDEACTIVATE, nr_active);
-
-                       nr_freed += shrink_page_list(&page_list, sc,
-                                                       PAGEOUT_IO_SYNC);
-               }
+               nr_active = clear_active_flags(&page_list, count);
+               count_vm_events(PGDEACTIVATE, nr_active);
 
-               nr_reclaimed += nr_freed;
+               nr_reclaimed += shrink_page_list(&page_list, sc, PAGEOUT_IO_SYNC);
+       }
 
-               local_irq_disable();
-               if (current_is_kswapd())
-                       __count_vm_events(KSWAPD_STEAL, nr_freed);
-               __count_zone_vm_events(PGSTEAL, zone, nr_freed);
+       local_irq_disable();
+       if (current_is_kswapd())
+               __count_vm_events(KSWAPD_STEAL, nr_reclaimed);
+       __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed);
 
-               spin_lock(&zone->lru_lock);
-               /*
-                * Put back any unfreeable pages.
-                */
-               while (!list_empty(&page_list)) {
-                       int lru;
-                       page = lru_to_page(&page_list);
-                       VM_BUG_ON(PageLRU(page));
-                       list_del(&page->lru);
-                       if (unlikely(!page_evictable(page, NULL))) {
-                               spin_unlock_irq(&zone->lru_lock);
-                               putback_lru_page(page);
-                               spin_lock_irq(&zone->lru_lock);
-                               continue;
-                       }
-                       SetPageLRU(page);
-                       lru = page_lru(page);
-                       add_page_to_lru_list(zone, page, lru);
-                       if (is_active_lru(lru)) {
-                               int file = is_file_lru(lru);
-                               reclaim_stat->recent_rotated[file]++;
-                       }
-                       if (!pagevec_add(&pvec, page)) {
-                               spin_unlock_irq(&zone->lru_lock);
-                               __pagevec_release(&pvec);
-                               spin_lock_irq(&zone->lru_lock);
-                       }
+       spin_lock(&zone->lru_lock);
+       /*
+        * Put back any unfreeable pages.
+        */
+       while (!list_empty(&page_list)) {
+               int lru;
+               page = lru_to_page(&page_list);
+               VM_BUG_ON(PageLRU(page));
+               list_del(&page->lru);
+               if (unlikely(!page_evictable(page, NULL))) {
+                       spin_unlock_irq(&zone->lru_lock);
+                       putback_lru_page(page);
+                       spin_lock_irq(&zone->lru_lock);
+                       continue;
                }
-               __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
-               __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
-
-       } while (nr_scanned < max_scan);
+               SetPageLRU(page);
+               lru = page_lru(page);
+               add_page_to_lru_list(zone, page, lru);
+               if (is_active_lru(lru)) {
+                       int file = is_file_lru(lru);
+                       reclaim_stat->recent_rotated[file]++;
+               }
+               if (!pagevec_add(&pvec, page)) {
+                       spin_unlock_irq(&zone->lru_lock);
+                       __pagevec_release(&pvec);
+                       spin_lock_irq(&zone->lru_lock);
+               }
+       }
+       __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
+       __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
 
 done:
        spin_unlock_irq(&zone->lru_lock);