Commit 31483b6a authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
Browse files

mm, vmscan: remove balance gap 

The balance gap was introduced to apply equal pressure to all zones when
reclaiming for a higher zone.  With node-based LRU, the need for the
balance gap is removed and the code is dead so remove it.

[vbabka@suse.cz: Also remove KSWAPD_ZONE_BALANCE_GAP_RATIO]
Link: http://lkml.kernel.org/r/1467970510-21195-9-git-send-email-mgorman@techsingularity.net


Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 1d82de61

include/linux/swap.h

+0 −9
Original line number Diff line number Diff line
@@ -157,15 +157,6 @@ enum { 
#define SWAP_CLUSTER_MAX 32UL

#define COMPACT_CLUSTER_MAX SWAP_CLUSTER_MAX



/*

 * 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



#define SWAP_MAP_MAX	0x3e	/* Max duplication count, in first swap_map */

#define SWAP_MAP_BAD	0x3f	/* Note pageblock is bad, in first swap_map */

#define SWAP_HAS_CACHE	0x40	/* Flag page is cached, in first swap_map */

mm/vmscan.c

+8 −11
Original line number Diff line number Diff line
@@ -2518,7 +2518,7 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc, 
 */

static inline bool compaction_ready(struct zone *zone, int order, int classzone_idx)

{

	unsigned long balance_gap, watermark;

	unsigned long watermark;

	bool watermark_ok;



	/*
@@ -2527,9 +2527,7 @@ static inline bool compaction_ready(struct zone *zone, int order, int classzone_ 
	 * 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), DIV_ROUND_UP(

			zone->managed_pages, KSWAPD_ZONE_BALANCE_GAP_RATIO));

	watermark = high_wmark_pages(zone) + balance_gap + (2UL << order);

	watermark = high_wmark_pages(zone) + (2UL << order);

	watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, classzone_idx);



	/*
@@ -3000,10 +2998,9 @@ static void age_active_anon(struct pglist_data *pgdat, 
	} while (memcg);

}



static bool zone_balanced(struct zone *zone, int order,

			unsigned long balance_gap, int classzone_idx)

static bool zone_balanced(struct zone *zone, int order, int classzone_idx)

{

	unsigned long mark = high_wmark_pages(zone) + balance_gap;

	unsigned long mark = high_wmark_pages(zone);



	return zone_watermark_ok_safe(zone, order, mark, classzone_idx);

}
@@ -3045,7 +3042,7 @@ static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining, 
		if (!populated_zone(zone))

			continue;



		if (zone_balanced(zone, order, 0, classzone_idx))

		if (zone_balanced(zone, order, classzone_idx))

			return true;

	}
@@ -3148,7 +3145,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx) 
				break;

			}



			if (!zone_balanced(zone, order, 0, 0)) {

			if (!zone_balanced(zone, order, 0)) {

				classzone_idx = i;

				break;

			} else {
@@ -3216,7 +3213,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx) 
			if (!populated_zone(zone))

				continue;



			if (zone_balanced(zone, sc.order, 0, classzone_idx)) {

			if (zone_balanced(zone, sc.order, classzone_idx)) {

				clear_bit(PGDAT_CONGESTED, &pgdat->flags);

				clear_bit(PGDAT_DIRTY, &pgdat->flags);

				goto out;
@@ -3427,7 +3424,7 @@ void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx) 
	}

	if (!waitqueue_active(&pgdat->kswapd_wait))

		return;

	if (zone_balanced(zone, order, 0, 0))

	if (zone_balanced(zone, order, 0))

		return;



	trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);

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