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authorJianyu Zhan <nasa4836@gmail.com>2014-06-04 16:10:38 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-06-04 16:54:11 -0700
commit4be89a34609659042ef0bf883ad76388fb5251bb (patch)
tree7a438185cb78e2c6d3aec1e64960e64188cb4afe
parentb7596fb43aa786fb3ee5015a73034fbb9e80feaa (diff)
downloadop-kernel-dev-4be89a34609659042ef0bf883ad76388fb5251bb.zip
op-kernel-dev-4be89a34609659042ef0bf883ad76388fb5251bb.tar.gz
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>
-rw-r--r--include/linux/swap.h8
-rw-r--r--mm/vmscan.c10
2 files changed, 8 insertions, 10 deletions
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 @@ enum {
#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
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 494cd63..cc29fca 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2295,9 +2295,8 @@ static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
* there is a buffer of free pages available to give compaction
* a reasonable chance of completing and allocating the page
*/
- balance_gap = min(low_wmark_pages(zone),
- (zone->managed_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
- KSWAPD_ZONE_BALANCE_GAP_RATIO);
+ balance_gap = min(low_wmark_pages(zone), DIV_ROUND_UP(
+ zone->managed_pages, KSWAPD_ZONE_BALANCE_GAP_RATIO));
watermark = high_wmark_pages(zone) + balance_gap + (2UL << sc->order);
watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 0, 0);
@@ -2949,9 +2948,8 @@ static bool kswapd_shrink_zone(struct zone *zone,
* high wmark plus a "gap" where the gap is either the low
* watermark or 1% of the zone, whichever is smaller.
*/
- balance_gap = min(low_wmark_pages(zone),
- (zone->managed_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
- KSWAPD_ZONE_BALANCE_GAP_RATIO);
+ balance_gap = min(low_wmark_pages(zone), DIV_ROUND_UP(
+ zone->managed_pages, KSWAPD_ZONE_BALANCE_GAP_RATIO));
/*
* If there is no low memory pressure or the zone is balanced then no
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