From df76cee6bbeb2ed036f1622f63a99c28cecf6b30 Mon Sep 17 00:00:00 2001 From: Vlastimil Babka Date: Fri, 24 Feb 2017 14:56:50 -0800 Subject: [PATCH] mm, page_alloc: remove redundant checks from alloc fastpath The allocation fast path contains two similar checks for zoneref->zone being NULL, where zoneref points either to the first zone in the zonelist, or to the preferred zone. These can be NULL either due to empty zonelist, or no zone being compatible with given nodemask or task's cpuset. These checks are unnecessary, because the zonelist walks in first_zones_zonelist() and get_page_from_freelist() handle a NULL starting zoneref->zone or preferred_zoneref->zone safely. It's safe to fallback to __alloc_pages_slowpath() where we also have the check early enough. Link: http://lkml.kernel.org/r/20170124150511.5710-1-vbabka@suse.cz Signed-off-by: Vlastimil Babka Cc: Michal Hocko Cc: Anshuman Khandual Cc: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 18 ------------------ 1 file changed, 18 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 6196eed96732..65876feb86f3 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3915,14 +3915,6 @@ static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order, if (should_fail_alloc_page(gfp_mask, order)) return false; - /* - * Check the zones suitable for the gfp_mask contain at least one - * valid zone. It's possible to have an empty zonelist as a result - * of __GFP_THISNODE and a memoryless node - */ - if (unlikely(!ac->zonelist->_zonerefs->zone)) - return false; - if (IS_ENABLED(CONFIG_CMA) && ac->migratetype == MIGRATE_MOVABLE) *alloc_flags |= ALLOC_CMA; @@ -3962,22 +3954,12 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, return NULL; finalise_ac(gfp_mask, order, &ac); - if (!ac.preferred_zoneref->zone) { - page = NULL; - /* - * This might be due to race with cpuset_current_mems_allowed - * update, so make sure we retry with original nodemask in the - * slow path. - */ - goto no_zone; - } /* First allocation attempt */ page = get_page_from_freelist(alloc_mask, order, alloc_flags, &ac); if (likely(page)) goto out; -no_zone: /* * Runtime PM, block IO and its error handling path can deadlock * because I/O on the device might not complete.