From 7fb2d46d396b2491818f8e43b01049b3234e6c07 Mon Sep 17 00:00:00 2001 From: Christoph Lameter Date: Wed, 22 Mar 2006 00:08:22 -0800 Subject: [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: Christoph Lameter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 2d5d4864de88..c712b946e4ff 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -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; } -- cgit v1.2.1