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Commit 0abdee2b authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
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mm: kswapd: use the order that kswapd was reclaiming at for sleeping_prematurely() 



Before kswapd goes to sleep, it uses sleeping_prematurely() to check if
there was a race pushing a zone below its watermark.  If the race
happened, it stays awake.  However, balance_pgdat() can decide to reclaim
at order-0 if it decides that high-order reclaim is not working as
expected.  This information is not passed back to sleeping_prematurely().
The impact is that kswapd remains awake reclaiming pages long after it
should have gone to sleep.  This patch passes the adjusted order to
sleeping_prematurely and uses the same logic as balance_pgdat to decide if
it's ok to go to sleep.

Signed-off-by: default avatarMel Gorman <mel@csn.ul.ie>
Reviewed-by: default avatarMinchan Kim <minchan.kim@gmail.com>
Reviewed-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: default avatarEric B Munson <emunson@mgebm.net>
Cc: Simon Kirby <sim@hostway.ca>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Shaohua Li <shaohua.li@intel.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 1741c877

mm/vmscan.c

+11 −5
Original line number Diff line number Diff line
@@ -2227,7 +2227,7 @@ static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages, 
}



/* is kswapd sleeping prematurely? */

static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)

static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining)

{

	int i;

	unsigned long balanced = 0;
@@ -2237,7 +2237,7 @@ static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining) 
	if (remaining)

		return 1;



	/* If after HZ/10, a zone is below the high mark, it's premature */

	/* Check the watermark levels */

	for (i = 0; i < pgdat->nr_zones; i++) {

		struct zone *zone = pgdat->node_zones + i;
@@ -2269,7 +2269,7 @@ static int sleeping_prematurely(pg_data_t *pgdat, int order, long remaining) 
 * For kswapd, balance_pgdat() will work across all this node's zones until

 * they are all at high_wmark_pages(zone).

 *

 * Returns the number of pages which were actually freed.

 * Returns the final order kswapd was reclaiming at

 *

 * There is special handling here for zones which are full of pinned pages.

 * This can happen if the pages are all mlocked, or if they are all used by
@@ -2532,7 +2532,13 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order, 
		}

	}



	return sc.nr_reclaimed;

	/*

	 * Return the order we were reclaiming at so sleeping_prematurely()

	 * makes a decision on the order we were last reclaiming at. However,

	 * if another caller entered the allocator slow path while kswapd

	 * was awake, order will remain at the higher level

	 */

	return order;

}



static void kswapd_try_to_sleep(pg_data_t *pgdat, int order)
@@ -2659,7 +2665,7 @@ static int kswapd(void *p) 
		 */

		if (!ret) {

			trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);

			balance_pgdat(pgdat, order, classzone_idx);

			order = balance_pgdat(pgdat, order, classzone_idx);

		}

	}

	return 0;