From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933291AbcLIJim (ORCPT ); Fri, 9 Dec 2016 04:38:42 -0500 Received: from mx2.suse.de ([195.135.220.15]:47839 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932349AbcLIJiV (ORCPT ); Fri, 9 Dec 2016 04:38:21 -0500 From: Vlastimil Babka To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Joonsoo Kim , Michal Hocko , Mel Gorman , "Kirill A. Shutemov" , Johannes Weiner , Vlastimil Babka Subject: [PATCH 1/2] mm, page_alloc: don't convert pfn to idx when merging Date: Fri, 9 Dec 2016 10:37:53 +0100 Message-Id: <20161209093754.3515-1-vbabka@suse.cz> X-Mailer: git-send-email 2.11.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In __free_one_page() we do the buddy merging arithmetics on "page/buddy index", which is just the lower MAX_ORDER bits of pfn. The operations we do that affect the higher bits are bitwise AND and subtraction (in that order), where the final result will be the same with the higher bits left unmasked, as long as these bits are equal for both buddies - which must be true by the definition of a buddy. We can therefore use pfn's directly instead of "index" and skip the zeroing of >MAX_ORDER bits. This can help a bit by itself, although compiler might be smart enough already. It also helps the next patch to avoid page_to_pfn() for memory hole checks. Signed-off-by: Vlastimil Babka --- mm/internal.h | 4 ++-- mm/page_alloc.c | 33 +++++++++++++++------------------ 2 files changed, 17 insertions(+), 20 deletions(-) diff --git a/mm/internal.h b/mm/internal.h index 537ac9951f5f..6d20f0e52b74 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -131,9 +131,9 @@ struct alloc_context { * Assumption: *_mem_map is contiguous at least up to MAX_ORDER */ static inline unsigned long -__find_buddy_index(unsigned long page_idx, unsigned int order) +__find_buddy_pfn(unsigned long page_pfn, unsigned int order) { - return page_idx ^ (1 << order); + return page_pfn ^ (1 << order); } extern struct page *__pageblock_pfn_to_page(unsigned long start_pfn, diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 6de9440e3ae2..812475bff8f3 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -783,13 +783,12 @@ static inline int page_is_buddy(struct page *page, struct page *buddy, */ static inline void __free_one_page(struct page *page, - unsigned long pfn, + unsigned long page_pfn, struct zone *zone, unsigned int order, int migratetype) { - unsigned long page_idx; - unsigned long combined_idx; - unsigned long uninitialized_var(buddy_idx); + unsigned long combined_pfn; + unsigned long uninitialized_var(buddy_pfn); struct page *buddy; unsigned int max_order; @@ -802,15 +801,13 @@ static inline void __free_one_page(struct page *page, if (likely(!is_migrate_isolate(migratetype))) __mod_zone_freepage_state(zone, 1 << order, migratetype); - page_idx = pfn & ((1 << MAX_ORDER) - 1); - - VM_BUG_ON_PAGE(page_idx & ((1 << order) - 1), page); + VM_BUG_ON_PAGE(page_pfn & ((1 << order) - 1), page); VM_BUG_ON_PAGE(bad_range(zone, page), page); continue_merging: while (order < max_order - 1) { - buddy_idx = __find_buddy_index(page_idx, order); - buddy = page + (buddy_idx - page_idx); + buddy_pfn = __find_buddy_pfn(page_pfn, order); + buddy = page + (buddy_pfn - page_pfn); if (!page_is_buddy(page, buddy, order)) goto done_merging; /* @@ -824,9 +821,9 @@ static inline void __free_one_page(struct page *page, zone->free_area[order].nr_free--; rmv_page_order(buddy); } - combined_idx = buddy_idx & page_idx; - page = page + (combined_idx - page_idx); - page_idx = combined_idx; + combined_pfn = buddy_pfn & page_pfn; + page = page + (combined_pfn - page_pfn); + page_pfn = combined_pfn; order++; } if (max_order < MAX_ORDER) { @@ -841,8 +838,8 @@ static inline void __free_one_page(struct page *page, if (unlikely(has_isolate_pageblock(zone))) { int buddy_mt; - buddy_idx = __find_buddy_index(page_idx, order); - buddy = page + (buddy_idx - page_idx); + buddy_pfn = __find_buddy_pfn(page_pfn, order); + buddy = page + (buddy_pfn - page_pfn); buddy_mt = get_pageblock_migratetype(buddy); if (migratetype != buddy_mt @@ -867,10 +864,10 @@ static inline void __free_one_page(struct page *page, */ if ((order < MAX_ORDER-2) && pfn_valid_within(page_to_pfn(buddy))) { struct page *higher_page, *higher_buddy; - combined_idx = buddy_idx & page_idx; - higher_page = page + (combined_idx - page_idx); - buddy_idx = __find_buddy_index(combined_idx, order + 1); - higher_buddy = higher_page + (buddy_idx - combined_idx); + combined_pfn = buddy_pfn & page_pfn; + higher_page = page + (combined_pfn - page_pfn); + buddy_pfn = __find_buddy_pfn(combined_pfn, order + 1); + higher_buddy = higher_page + (buddy_pfn - combined_pfn); if (page_is_buddy(higher_page, higher_buddy, order + 1)) { list_add_tail(&page->lru, &zone->free_area[order].free_list[migratetype]); -- 2.11.0