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Subject[PATCH 2/3] mm: shrink_inactive_lis() nr_scan accounting fix fix
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Subject: [PATCH] mm: shrink_inactive_lis() nr_scan accounting fix fix

If sc->isolate_pages() return 0, we don't need to call shrink_page_list().
In past days, shrink_inactive_list() handled it properly.

But commit fb8d14e1 (three years ago commit!) breaked it. current shrink_inactive_list()
always call shrink_page_list() although isolate_pages() return 0.

This patch restore proper return value check.


Requirements:
o "nr_taken == 0" condition should stay before calling shrink_page_list().
o "nr_taken == 0" condition should stay after nr_scan related statistics
modification.


Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
---
mm/vmscan.c | 30 ++++++++++++++++++------------
1 file changed, 18 insertions(+), 12 deletions(-)
Index: b/mm/vmscan.c
===================================================================
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1071,6 +1071,20 @@ static unsigned long shrink_inactive_lis
nr_taken = sc->isolate_pages(sc->swap_cluster_max,
&page_list, &nr_scan, sc->order, mode,
zone, sc->mem_cgroup, 0, file);
+
+ if (scanning_global_lru(sc)) {
+ 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);
+ }
+
+ if (nr_taken == 0)
+ goto done;
+
nr_active = clear_active_flags(&page_list, count);
__count_vm_events(PGDEACTIVATE, nr_active);

@@ -1083,8 +1097,6 @@ static unsigned long shrink_inactive_lis
__mod_zone_page_state(zone, NR_INACTIVE_ANON,
-count[LRU_INACTIVE_ANON]);

- if (scanning_global_lru(sc))
- zone->pages_scanned += nr_scan;

reclaim_stat->recent_scanned[0] += count[LRU_INACTIVE_ANON];
reclaim_stat->recent_scanned[0] += count[LRU_ACTIVE_ANON];
@@ -1118,18 +1130,12 @@ static unsigned long shrink_inactive_lis
}

nr_reclaimed += nr_freed;
+
local_irq_disable();
- if (current_is_kswapd()) {
- __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan);
+ if (current_is_kswapd())
__count_vm_events(KSWAPD_STEAL, nr_freed);
- } else if (scanning_global_lru(sc))
- __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan);
-
__count_zone_vm_events(PGSTEAL, zone, nr_freed);

- if (nr_taken == 0)
- goto done;
-
spin_lock(&zone->lru_lock);
/*
* Put back any unfreeable pages.
@@ -1159,9 +1165,9 @@ static unsigned long shrink_inactive_lis
}
}
} while (nr_scanned < max_scan);
- spin_unlock(&zone->lru_lock);
+
done:
- local_irq_enable();
+ spin_unlock_irq(&zone->lru_lock);
pagevec_release(&pvec);
return nr_reclaimed;
}



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