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Commit 4ae0a48b authored by Zlatko Calusic's avatar Zlatko Calusic Committed by Linus Torvalds
Browse files

mm: modify pgdat_balanced() so that it also handles order-0 



Teach pgdat_balanced() about order-0 allocations so that we can simplify
code in a few places in vmstat.c.

Suggested-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarZlatko Calusic <zlatko.calusic@iskon.hr>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9c016d61

mm/vmscan.c

+45 −60
Original line number Diff line number Diff line
@@ -2452,12 +2452,16 @@ static bool zone_balanced(struct zone *zone, int order, 
}



/*

 * pgdat_balanced is used when checking if a node is balanced for high-order

 * allocations. Only zones that meet watermarks and are in a zone allowed

 * by the callers classzone_idx are added to balanced_pages. The total of

 * balanced pages must be at least 25% of the zones allowed by classzone_idx

 * for the node to be considered balanced. Forcing all zones to be balanced

 * for high orders can cause excessive reclaim when there are imbalanced zones.

 * pgdat_balanced() is used when checking if a node is balanced.

 *

 * For order-0, all zones must be balanced!

 *

 * For high-order allocations only zones that meet watermarks and are in a

 * zone allowed by the callers classzone_idx are added to balanced_pages. The

 * total of balanced pages must be at least 25% of the zones allowed by

 * classzone_idx for the node to be considered balanced. Forcing all zones to

 * be balanced for high orders can cause excessive reclaim when there are

 * imbalanced zones.

 * The choice of 25% is due to

 *   o a 16M DMA zone that is balanced will not balance a zone on any

 *     reasonable sized machine
@@ -2467,17 +2471,43 @@ static bool zone_balanced(struct zone *zone, int order, 
 *     Similarly, on x86-64 the Normal zone would need to be at least 1G

 *     to balance a node on its own. These seemed like reasonable ratios.

 */

static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages,

						int classzone_idx)

static bool pgdat_balanced(pg_data_t *pgdat, int order, int classzone_idx)

{

	unsigned long present_pages = 0;

	unsigned long balanced_pages = 0;

	int i;



	for (i = 0; i <= classzone_idx; i++)

		present_pages += pgdat->node_zones[i].present_pages;

	/* Check the watermark levels */

	for (i = 0; i <= classzone_idx; i++) {

		struct zone *zone = pgdat->node_zones + i;



		if (!populated_zone(zone))

			continue;



		present_pages += zone->present_pages;



		/*

		 * A special case here:

		 *

		 * balance_pgdat() skips over all_unreclaimable after

		 * DEF_PRIORITY. Effectively, it considers them balanced so

		 * they must be considered balanced here as well!

		 */

		if (zone->all_unreclaimable) {

			balanced_pages += zone->present_pages;

			continue;

		}



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

			balanced_pages += zone->present_pages;

		else if (!order)

			return false;

	}



	/* A special case here: if zone has no page, we think it's balanced */

	if (order)

		return balanced_pages >= (present_pages >> 2);

	else

		return true;

}



/*
@@ -2489,10 +2519,6 @@ static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages, 
static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining,

					int classzone_idx)

{

	int i;

	unsigned long balanced = 0;

	bool all_zones_ok = true;



	/* If a direct reclaimer woke kswapd within HZ/10, it's premature */

	if (remaining)

		return false;
@@ -2511,39 +2537,7 @@ static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining, 
		return false;

	}



	/* Check the watermark levels */

	for (i = 0; i <= classzone_idx; i++) {

		struct zone *zone = pgdat->node_zones + i;



		if (!populated_zone(zone))

			continue;



		/*

		 * balance_pgdat() skips over all_unreclaimable after

		 * DEF_PRIORITY. Effectively, it considers them balanced so

		 * they must be considered balanced here as well if kswapd

		 * is to sleep

		 */

		if (zone->all_unreclaimable) {

			balanced += zone->present_pages;

			continue;

		}



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

			all_zones_ok = false;

		else

			balanced += zone->present_pages;

	}



	/*

	 * For high-order requests, the balanced zones must contain at least

	 * 25% of the nodes pages for kswapd to sleep. For order-0, all zones

	 * must be balanced

	 */

	if (order)

		return pgdat_balanced(pgdat, balanced, classzone_idx);

	else

		return all_zones_ok;

	return pgdat_balanced(pgdat, order, classzone_idx);

}



/*
@@ -2571,7 +2565,6 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order, 
							int *classzone_idx)

{

	struct zone *unbalanced_zone;

	unsigned long balanced;

	int i;

	int end_zone = 0;	/* Inclusive.  0 = ZONE_DMA */

	unsigned long total_scanned;
@@ -2605,7 +2598,6 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order, 
		int has_under_min_watermark_zone = 0;



		unbalanced_zone = NULL;

		balanced = 0;



		/*

		 * Scan in the highmem->dma direction for the highest
@@ -2761,8 +2753,6 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order, 
				 * speculatively avoid congestion waits

				 */

				zone_clear_flag(zone, ZONE_CONGESTED);

				if (i <= *classzone_idx)

					balanced += zone->present_pages;

			}



		}
@@ -2776,7 +2766,7 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order, 
				pfmemalloc_watermark_ok(pgdat))

			wake_up(&pgdat->pfmemalloc_wait);



		if (!unbalanced_zone || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))

		if (pgdat_balanced(pgdat, order, *classzone_idx))

			break;		/* kswapd: all done */

		/*

		 * OK, kswapd is getting into trouble.  Take a nap, then take
@@ -2800,12 +2790,7 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order, 
	} while (--sc.priority >= 0);

out:



	/*

	 * order-0: All zones must meet high watermark for a balanced node

	 * high-order: Balanced zones must make up at least 25% of the node

	 *             for the node to be balanced

	 */

	if (unbalanced_zone && (!order || !pgdat_balanced(pgdat, balanced, *classzone_idx))) {

	if (!pgdat_balanced(pgdat, order, *classzone_idx)) {

		cond_resched();



		try_to_freeze();