2.6.30-stable review patch. If anyone has any objections, please let us know. ------------------ From: Mel Gorman commit fa5e084e43eb14c14942027e1e2e894aeed96097 upstream. vmscan: do not unconditionally treat zones that fail zone_reclaim() as full On NUMA machines, the administrator can configure zone_reclaim_mode that is a more targetted form of direct reclaim. On machines with large NUMA distances for example, a zone_reclaim_mode defaults to 1 meaning that clean unmapped pages will be reclaimed if the zone watermarks are not being met. The problem is that zone_reclaim() failing at all means the zone gets marked full. This can cause situations where a zone is usable, but is being skipped because it has been considered full. Take a situation where a large tmpfs mount is occuping a large percentage of memory overall. The pages do not get cleaned or reclaimed by zone_reclaim(), but the zone gets marked full and the zonelist cache considers them not worth trying in the future. This patch makes zone_reclaim() return more fine-grained information about what occured when zone_reclaim() failued. The zone only gets marked full if it really is unreclaimable. If it's a case that the scan did not occur or if enough pages were not reclaimed with the limited reclaim_mode, then the zone is simply skipped. There is a side-effect to this patch. Currently, if zone_reclaim() successfully reclaimed SWAP_CLUSTER_MAX, an allocation attempt would go ahead. With this patch applied, zone watermarks are rechecked after zone_reclaim() does some work. This bug was introduced by commit 9276b1bc96a132f4068fdee00983c532f43d3a26 ("memory page_alloc zonelist caching speedup") way back in 2.6.19 when the zonelist_cache was introduced. It was not intended that zone_reclaim() aggressively consider the zone to be full when it failed as full direct reclaim can still be an option. Due to the age of the bug, it should be considered a -stable candidate. Signed-off-by: Mel Gorman Reviewed-by: Wu Fengguang Reviewed-by: Rik van Riel Reviewed-by: KOSAKI Motohiro Cc: Christoph Lameter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/internal.h | 4 ++++ mm/page_alloc.c | 26 ++++++++++++++++++++++---- mm/vmscan.c | 11 ++++++----- 3 files changed, 32 insertions(+), 9 deletions(-) --- a/mm/internal.h +++ b/mm/internal.h @@ -284,4 +284,8 @@ int __get_user_pages(struct task_struct unsigned long start, int len, int flags, struct page **pages, struct vm_area_struct **vmas); +#define ZONE_RECLAIM_NOSCAN -2 +#define ZONE_RECLAIM_FULL -1 +#define ZONE_RECLAIM_SOME 0 +#define ZONE_RECLAIM_SUCCESS 1 #endif --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1420,20 +1420,38 @@ zonelist_scan: if (!(alloc_flags & ALLOC_NO_WATERMARKS)) { unsigned long mark; + int ret; if (alloc_flags & ALLOC_WMARK_MIN) mark = zone->pages_min; else if (alloc_flags & ALLOC_WMARK_LOW) mark = zone->pages_low; else mark = zone->pages_high; - if (!zone_watermark_ok(zone, order, mark, - classzone_idx, alloc_flags)) { - if (!zone_reclaim_mode || - !zone_reclaim(zone, gfp_mask, order)) + + if (zone_watermark_ok(zone, order, mark, + classzone_idx, alloc_flags)) + goto try_this_zone; + + if (zone_reclaim_mode == 0) + goto this_zone_full; + + ret = zone_reclaim(zone, gfp_mask, order); + switch (ret) { + case ZONE_RECLAIM_NOSCAN: + /* did not scan */ + goto try_next_zone; + case ZONE_RECLAIM_FULL: + /* scanned but unreclaimable */ + goto this_zone_full; + default: + /* did we reclaim enough */ + if (!zone_watermark_ok(zone, order, mark, + classzone_idx, alloc_flags)) goto this_zone_full; } } +try_this_zone: page = buffered_rmqueue(preferred_zone, zone, order, gfp_mask); if (page) break; --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2426,16 +2426,16 @@ int zone_reclaim(struct zone *zone, gfp_ */ if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages && zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages) - return 0; + return ZONE_RECLAIM_FULL; if (zone_is_all_unreclaimable(zone)) - return 0; + return ZONE_RECLAIM_FULL; /* * Do not scan if the allocation should not be delayed. */ if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) - return 0; + return ZONE_RECLAIM_NOSCAN; /* * Only run zone reclaim on the local zone or on zones that do not @@ -2445,10 +2445,11 @@ int zone_reclaim(struct zone *zone, gfp_ */ node_id = zone_to_nid(zone); if (node_state(node_id, N_CPU) && node_id != numa_node_id()) - return 0; + return ZONE_RECLAIM_NOSCAN; if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED)) - return 0; + return ZONE_RECLAIM_NOSCAN; + ret = __zone_reclaim(zone, gfp_mask, order); zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/