Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756500AbbBQJmk (ORCPT ); Tue, 17 Feb 2015 04:42:40 -0500 Received: from cantor2.suse.de ([195.135.220.15]:50990 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752058AbbBQJmi (ORCPT ); Tue, 17 Feb 2015 04:42:38 -0500 Message-ID: <54E30D0B.1050805@suse.cz> Date: Tue, 17 Feb 2015 10:42:35 +0100 From: Vlastimil Babka User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 MIME-Version: 1.0 To: Joonsoo Kim , Andrew Morton CC: Mel Gorman , David Rientjes , Rik van Riel , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Zhang Yanfei Subject: Re: [PATCH v4 2/3] mm/page_alloc: factor out fallback freepage checking References: <1423725305-3726-1-git-send-email-iamjoonsoo.kim@lge.com> <1423725305-3726-2-git-send-email-iamjoonsoo.kim@lge.com> In-Reply-To: <1423725305-3726-2-git-send-email-iamjoonsoo.kim@lge.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7155 Lines: 205 On 02/12/2015 08:15 AM, Joonsoo Kim wrote: > This is preparation step to use page allocator's anti fragmentation logic > in compaction. This patch just separates fallback freepage checking part > from fallback freepage management part. Therefore, there is no functional > change. > > Signed-off-by: Joonsoo Kim Acked-by: Vlastimil Babka > --- > mm/page_alloc.c | 143 +++++++++++++++++++++++++++++++++++-------------------- > 1 file changed, 91 insertions(+), 52 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index e64b260..64a4974 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1142,14 +1142,40 @@ static void change_pageblock_range(struct page *pageblock_page, > * as fragmentation caused by those allocations polluting movable pageblocks > * is worse than movable allocations stealing from unmovable and reclaimable > * pageblocks. > - * > - * If we claim more than half of the pageblock, change pageblock's migratetype > - * as well. > */ > -static void try_to_steal_freepages(struct zone *zone, struct page *page, > - int start_type, int fallback_type) > +static bool can_steal_fallback(unsigned int order, int start_mt) > +{ > + /* > + * Leaving this order check is intended, although there is > + * relaxed order check in next check. The reason is that > + * we can actually steal whole pageblock if this condition met, > + * but, below check doesn't guarantee it and that is just heuristic > + * so could be changed anytime. > + */ > + if (order >= pageblock_order) > + return true; > + > + if (order >= pageblock_order / 2 || > + start_mt == MIGRATE_RECLAIMABLE || > + start_mt == MIGRATE_UNMOVABLE || > + page_group_by_mobility_disabled) > + return true; > + > + return false; > +} > + > +/* > + * This function implements actual steal behaviour. If order is large enough, > + * we can steal whole pageblock. If not, we first move freepages in this > + * pageblock and check whether half of pages are moved or not. If half of > + * pages are moved, we can change migratetype of pageblock and permanently > + * use it's pages as requested migratetype in the future. > + */ > +static void steal_suitable_fallback(struct zone *zone, struct page *page, > + int start_type) > { > int current_order = page_order(page); > + int pages; > > /* Take ownership for orders >= pageblock_order */ > if (current_order >= pageblock_order) { > @@ -1157,19 +1183,40 @@ static void try_to_steal_freepages(struct zone *zone, struct page *page, > return; > } > > - if (current_order >= pageblock_order / 2 || > - start_type == MIGRATE_RECLAIMABLE || > - start_type == MIGRATE_UNMOVABLE || > - page_group_by_mobility_disabled) { > - int pages; > + pages = move_freepages_block(zone, page, start_type); > + > + /* Claim the whole block if over half of it is free */ > + if (pages >= (1 << (pageblock_order-1)) || > + page_group_by_mobility_disabled) > + set_pageblock_migratetype(page, start_type); > +} > + > +/* Check whether there is a suitable fallback freepage with requested order. */ > +static int find_suitable_fallback(struct free_area *area, unsigned int order, > + int migratetype, bool *can_steal) > +{ > + int i; > + int fallback_mt; > + > + if (area->nr_free == 0) > + return -1; > + > + *can_steal = false; > + for (i = 0;; i++) { > + fallback_mt = fallbacks[migratetype][i]; > + if (fallback_mt == MIGRATE_RESERVE) > + break; > + > + if (list_empty(&area->free_list[fallback_mt])) > + continue; > > - pages = move_freepages_block(zone, page, start_type); > + if (can_steal_fallback(order, migratetype)) > + *can_steal = true; > > - /* Claim the whole block if over half of it is free */ > - if (pages >= (1 << (pageblock_order-1)) || > - page_group_by_mobility_disabled) > - set_pageblock_migratetype(page, start_type); > + return fallback_mt; > } > + > + return -1; > } > > /* Remove an element from the buddy allocator from the fallback list */ > @@ -1179,53 +1226,45 @@ __rmqueue_fallback(struct zone *zone, unsigned int order, int start_migratetype) > struct free_area *area; > unsigned 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; > --current_order) { > - int i; > - for (i = 0;; i++) { > - int migratetype = fallbacks[start_migratetype][i]; > - int buddy_type = start_migratetype; > - > - /* MIGRATE_RESERVE handled later if necessary */ > - if (migratetype == MIGRATE_RESERVE) > - break; > - > - area = &(zone->free_area[current_order]); > - if (list_empty(&area->free_list[migratetype])) > - continue; > - > - page = list_entry(area->free_list[migratetype].next, > - struct page, lru); > - area->nr_free--; > - > - try_to_steal_freepages(zone, page, start_migratetype, > - migratetype); > + area = &(zone->free_area[current_order]); > + fallback_mt = find_suitable_fallback(area, current_order, > + start_migratetype, &can_steal); > + if (fallback_mt == -1) > + continue; > > - /* Remove the page from the freelists */ > - list_del(&page->lru); > - rmv_page_order(page); > + page = list_entry(area->free_list[fallback_mt].next, > + struct page, lru); > + if (can_steal) > + steal_suitable_fallback(zone, page, start_migratetype); > > - expand(zone, page, order, current_order, area, > - buddy_type); > + /* Remove the page from the freelists */ > + area->nr_free--; > + list_del(&page->lru); > + rmv_page_order(page); > > - /* > - * The freepage_migratetype may differ from pageblock's > - * migratetype depending on the decisions in > - * try_to_steal_freepages(). This is OK as long as it > - * does not differ for MIGRATE_CMA pageblocks. For CMA > - * we need to make sure unallocated pages flushed from > - * pcp lists are returned to the correct freelist. > - */ > - set_freepage_migratetype(page, buddy_type); > + expand(zone, page, order, current_order, area, > + start_migratetype); > + /* > + * The freepage_migratetype may differ from pageblock's > + * migratetype depending on the decisions in > + * try_to_steal_freepages(). This is OK as long as it > + * does not differ for MIGRATE_CMA pageblocks. For CMA > + * we need to make sure unallocated pages flushed from > + * pcp lists are returned to the correct freelist. > + */ > + set_freepage_migratetype(page, start_migratetype); > > - trace_mm_page_alloc_extfrag(page, order, current_order, > - start_migratetype, migratetype); > + trace_mm_page_alloc_extfrag(page, order, current_order, > + start_migratetype, fallback_mt); > > - return page; > - } > + return page; > } > > return NULL; > -- 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/