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Commit 7fb2d46d authored by Christoph Lameter's avatar Christoph Lameter Committed by Linus Torvalds
Browse files

[PATCH] zone_reclaim: additional comments and cleanup 



Add some comments to explain how zone reclaim works.  And it fixes the
following issues:

- PF_SWAPWRITE needs to be set for RECLAIM_SWAP to be able to write
  out pages to swap. Currently RECLAIM_SWAP may not do that.

- remove setting nr_reclaimed pages after slab reclaim since the slab shrinking
  code does not use that and the nr_reclaimed pages is just right for the
  intended follow up action.

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 1742f19f

mm/vmscan.c

+14 −4
Original line number Diff line number Diff line
@@ -1887,6 +1887,7 @@ int zone_reclaim_interval __read_mostly = 30*HZ; 
 */

static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)

{

	/* Minimum pages needed in order to stay on node */

	const unsigned long nr_pages = 1 << order;

	struct task_struct *p = current;

	struct reclaim_state reclaim_state;
@@ -1924,9 +1925,12 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 


	if (nr_reclaimed < nr_pages && (zone_reclaim_mode & RECLAIM_SLAB)) {

		/*

		 * shrink_slab does not currently allow us to determine

		 * how many pages were freed in the zone. So we just

		 * shake the slab and then go offnode for a single allocation.

		 * shrink_slab() does not currently allow us to determine how

		 * many pages were freed in this zone. So we just shake the slab

		 * a bit and then go off node for this particular allocation

		 * despite possibly having freed enough memory to allocate in

		 * this zone.  If we freed local memory then the next

		 * allocations will be local again.

		 *

		 * shrink_slab will free memory on all zones and may take

		 * a long time.
@@ -1937,8 +1941,14 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) 
	p->reclaim_state = NULL;

	current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);



	if (nr_reclaimed == 0)

	if (nr_reclaimed == 0) {

		/*

		 * We were unable to reclaim enough pages to stay on node.  We

		 * now allow off node accesses for a certain time period before

		 * trying again to reclaim pages from the local zone.

		 */

		zone->last_unsuccessful_zone_reclaim = jiffies;

	}



	return nr_reclaimed >= nr_pages;

}