mm: modify pgdat_balanced() so that it also handles order-0 (4ae0a48b) · Commits · 戴 / test

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 @@ loop_again:
		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 @@ loop_again:
		* speculatively avoid congestion waits
		*/
		zone_clear_flag(zone, ZONE_CONGESTED);
		if (i <= *classzone_idx)
		balanced += zone->present_pages;
		}

		}
		@@ -2776,7 +2766,7 @@ loop_again:
		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 @@ loop_again:
		} 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();

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