mm/vmscan.c: use DIV_ROUND_UP for calculation of zone's balance_gap and correct comments.
Currently, we use (zone->managed_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1)
/ KSWAPD_ZONE_BALANCE_GAP_RATIO to avoid a zero gap value. It's better to
use DIV_ROUND_UP macro for neater code and clear meaning.
Besides, the gap value is calculated against the per-zone "managed pages",
not "present pages". This patch also corrects the comment and do some
rephrasing.
Signed-off-by: Jianyu Zhan <nasa4836@gmail.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Rafael Aquini <aquini@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 4348d95..4bdbee8 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -166,10 +166,10 @@
#define COMPACT_CLUSTER_MAX SWAP_CLUSTER_MAX
/*
- * Ratio between the present memory in the zone and the "gap" that
- * we're allowing kswapd to shrink in addition to the per-zone high
- * wmark, even for zones that already have the high wmark satisfied,
- * in order to provide better per-zone lru behavior. We are ok to
+ * Ratio between zone->managed_pages and the "gap" that above the per-zone
+ * "high_wmark". While balancing nodes, We allow kswapd to shrink zones that
+ * do not meet the (high_wmark + gap) watermark, even which already met the
+ * high_wmark, in order to provide better per-zone lru behavior. We are ok to
* spend not more than 1% of the memory for this zone balancing "gap".
*/
#define KSWAPD_ZONE_BALANCE_GAP_RATIO 100