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[PATCH] zone_reclaim: additional comments and cleanup

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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: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Christoph Lameter 2006-03-22 00:08:22 -08:00 committed by Linus Torvalds
parent 1742f19fa9
commit 7fb2d46d39
1 changed files with 14 additions and 4 deletions
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18
mm/vmscan.c
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@ -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;
}