diff options
Diffstat (limited to 'mm/page_alloc.c')
| -rw-r--r-- | mm/page_alloc.c | 80 |
1 files changed, 63 insertions, 17 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index bd65b60939b6..6d30e914afb6 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2206,19 +2206,26 @@ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac, * list of requested migratetype, possibly along with other pages from the same * block, depending on fragmentation avoidance heuristics. Returns true if * fallback was found so that __rmqueue_smallest() can grab it. + * + * The use of signed ints for order and current_order is a deliberate + * deviation from the rest of this file, to make the for loop + * condition simpler. */ static inline bool -__rmqueue_fallback(struct zone *zone, unsigned int order, int start_migratetype) +__rmqueue_fallback(struct zone *zone, int order, int start_migratetype) { struct free_area *area; - unsigned int current_order; + int current_order; struct page *page; int fallback_mt; bool can_steal; - /* Find the largest possible block of pages in the other list */ - for (current_order = MAX_ORDER-1; - current_order >= order && current_order <= MAX_ORDER-1; + /* + * Find the largest available free page in the other list. This roughly + * approximates finding the pageblock with the most free pages, which + * would be too costly to do exactly. + */ + for (current_order = MAX_ORDER - 1; current_order >= order; --current_order) { area = &(zone->free_area[current_order]); fallback_mt = find_suitable_fallback(area, current_order, @@ -2226,19 +2233,50 @@ __rmqueue_fallback(struct zone *zone, unsigned int order, int start_migratetype) if (fallback_mt == -1) continue; - page = list_first_entry(&area->free_list[fallback_mt], - struct page, lru); + /* + * We cannot steal all free pages from the pageblock and the + * requested migratetype is movable. In that case it's better to + * steal and split the smallest available page instead of the + * largest available page, because even if the next movable + * allocation falls back into a different pageblock than this + * one, it won't cause permanent fragmentation. + */ + if (!can_steal && start_migratetype == MIGRATE_MOVABLE + && current_order > order) + goto find_smallest; - steal_suitable_fallback(zone, page, start_migratetype, - can_steal); + goto do_steal; + } - trace_mm_page_alloc_extfrag(page, order, current_order, - start_migratetype, fallback_mt); + return false; - return true; +find_smallest: + for (current_order = order; current_order < MAX_ORDER; + current_order++) { + area = &(zone->free_area[current_order]); + fallback_mt = find_suitable_fallback(area, current_order, + start_migratetype, false, &can_steal); + if (fallback_mt != -1) + break; } - return false; + /* + * This should not happen - we already found a suitable fallback + * when looking for the largest page. + */ + VM_BUG_ON(current_order == MAX_ORDER); + +do_steal: + page = list_first_entry(&area->free_list[fallback_mt], + struct page, lru); + + steal_suitable_fallback(zone, page, start_migratetype, can_steal); + + trace_mm_page_alloc_extfrag(page, order, current_order, + start_migratetype, fallback_mt); + + return true; + } /* @@ -3246,6 +3284,14 @@ __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order, /* The OOM killer will not help higher order allocs */ if (order > PAGE_ALLOC_COSTLY_ORDER) goto out; + /* + * We have already exhausted all our reclaim opportunities without any + * success so it is time to admit defeat. We will skip the OOM killer + * because it is very likely that the caller has a more reasonable + * fallback than shooting a random task. + */ + if (gfp_mask & __GFP_RETRY_MAYFAIL) + goto out; /* The OOM killer does not needlessly kill tasks for lowmem */ if (ac->high_zoneidx < ZONE_NORMAL) goto out; @@ -3375,7 +3421,7 @@ should_compact_retry(struct alloc_context *ac, int order, int alloc_flags, } /* - * !costly requests are much more important than __GFP_REPEAT + * !costly requests are much more important than __GFP_RETRY_MAYFAIL * costly ones because they are de facto nofail and invoke OOM * killer to move on while costly can fail and users are ready * to cope with that. 1/4 retries is rather arbitrary but we @@ -3882,9 +3928,9 @@ retry: /* * Do not retry costly high order allocations unless they are - * __GFP_REPEAT + * __GFP_RETRY_MAYFAIL */ - if (costly_order && !(gfp_mask & __GFP_REPEAT)) + if (costly_order && !(gfp_mask & __GFP_RETRY_MAYFAIL)) goto nopage; if (should_reclaim_retry(gfp_mask, order, ac, alloc_flags, @@ -5240,7 +5286,7 @@ void __ref build_all_zonelists(pg_data_t *pgdat, struct zone *zone) #endif /* we have to stop all cpus to guarantee there is no user of zonelist */ - stop_machine(__build_all_zonelists, pgdat, NULL); + stop_machine_cpuslocked(__build_all_zonelists, pgdat, NULL); /* cpuset refresh routine should be here */ } vm_total_pages = nr_free_pagecache_pages(); |