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Commit 89288623 authored by Christoph Lameter's avatar Christoph Lameter Committed by Linus Torvalds
Browse files

[PATCH] Optimize off-node performance of zone reclaim 



Ensure that the performance of off node pages stays the same as before.
Off node pagefault tests showed an 18% drop in performance without this
patch.

- Increase the timeout to 30 seconds to reduce the overhead.

- Move all code possible out of the off node hot path for zone reclaim
  (Sorry Andrew, the struct initialization had to be sacrificed).
  The read_page_state() bit us there.

- Check first for the timeout before any other checks.

Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 537421be

mm/vmscan.c

+15 −14
Original line number Diff line number Diff line
@@ -1589,24 +1589,20 @@ int zone_reclaim_mode __read_mostly; 
/*

 * Mininum time between zone reclaim scans

 */

#define ZONE_RECLAIM_INTERVAL HZ/2

#define ZONE_RECLAIM_INTERVAL 30*HZ

/*

 * Try to free up some pages from this zone through reclaim.

 */

int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)

{

	int nr_pages = 1 << order;

	int nr_pages;

	struct task_struct *p = current;

	struct reclaim_state reclaim_state;

	struct scan_control sc = {

		.gfp_mask	= gfp_mask,

		.may_writepage	= 0,

		.may_swap	= 0,

		.nr_mapped	= read_page_state(nr_mapped),

		.nr_scanned	= 0,

		.nr_reclaimed	= 0,

		.priority	= 0

	};

	struct scan_control sc;



	if (time_before(jiffies,

		zone->last_unsuccessful_zone_reclaim + ZONE_RECLAIM_INTERVAL))

			return 0;



	if (!(gfp_mask & __GFP_WAIT) ||

		zone->zone_pgdat->node_id != numa_node_id() ||
@@ -1614,12 +1610,17 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 
		atomic_read(&zone->reclaim_in_progress) > 0)

			return 0;



	if (time_before(jiffies,

		zone->last_unsuccessful_zone_reclaim + ZONE_RECLAIM_INTERVAL))

			return 0;

	sc.may_writepage = 0;

	sc.may_swap = 0;

	sc.nr_scanned = 0;

	sc.nr_reclaimed = 0;

	sc.priority = 0;

	sc.nr_mapped = read_page_state(nr_mapped);

	sc.gfp_mask = gfp_mask;



	disable_swap_token();



	nr_pages = 1 << order;

	if (nr_pages > SWAP_CLUSTER_MAX)

		sc.swap_cluster_max = nr_pages;

	else