From d773ed6b856a96bd6d18b6e04455e3ced0876da4 Mon Sep 17 00:00:00 2001 From: David Rientjes Date: Tue, 16 Oct 2007 23:26:01 -0700 Subject: mm: test and set zone reclaim lock before starting reclaim Introduces new zone flag interface for testing and setting flags: int zone_test_and_set_flag(struct zone *zone, zone_flags_t flag) Instead of setting and clearing ZONE_RECLAIM_LOCKED each time shrink_zone() is called, this flag is test and set before starting zone reclaim. Zone reclaim starts in __alloc_pages() when a zone's watermark fails and the system is in zone_reclaim_mode. If it's already in reclaim, there's no need to start again so it is simply considered full for that allocation attempt. There is a change of behavior with regard to concurrent zone shrinking. It is now possible for try_to_free_pages() or kswapd to already be shrinking a particular zone when __alloc_pages() starts zone reclaim. In this case, it is possible for two concurrent threads to invoke shrink_zone() for a single zone. This change forbids a zone to be in zone reclaim twice, which was always the behavior, but allows for concurrent try_to_free_pages() or kswapd shrinking when starting zone reclaim. Cc: Andrea Arcangeli Cc: Christoph Lameter Signed-off-by: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 23 +++++++++++++---------- 1 file changed, 13 insertions(+), 10 deletions(-) (limited to 'mm/vmscan.c') diff --git a/mm/vmscan.c b/mm/vmscan.c index d8893dc2d4eb..e1471385d001 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1108,8 +1108,6 @@ static unsigned long shrink_zone(int priority, struct zone *zone, unsigned long nr_to_scan; unsigned long nr_reclaimed = 0; - zone_set_flag(zone, ZONE_RECLAIM_LOCKED); - /* * Add one to `nr_to_scan' just to make sure that the kernel will * slowly sift through the active list. @@ -1148,8 +1146,6 @@ static unsigned long shrink_zone(int priority, struct zone *zone, } throttle_vm_writeout(sc->gfp_mask); - - zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); return nr_reclaimed; } @@ -1900,6 +1896,7 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) { int node_id; + int ret; /* * Zone reclaim reclaims unmapped file backed pages and @@ -1917,13 +1914,13 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) <= zone->min_slab_pages) return 0; + if (zone_is_all_unreclaimable(zone)) + return 0; + /* - * Avoid concurrent zone reclaims, do not reclaim in a zone that does - * not have reclaimable pages and if we should not delay the allocation - * then do not scan. + * Do not scan if the allocation should not be delayed. */ - if (!(gfp_mask & __GFP_WAIT) || zone_is_all_unreclaimable(zone) || - zone_is_reclaim_locked(zone) || (current->flags & PF_MEMALLOC)) + if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) return 0; /* @@ -1935,6 +1932,12 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) node_id = zone_to_nid(zone); if (node_state(node_id, N_CPU) && node_id != numa_node_id()) return 0; - return __zone_reclaim(zone, gfp_mask, order); + + if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED)) + return 0; + ret = __zone_reclaim(zone, gfp_mask, order); + zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); + + return ret; } #endif -- cgit v1.2.3-59-g8ed1b