Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755092Ab2KUPKL (ORCPT ); Wed, 21 Nov 2012 10:10:11 -0500 Received: from mail-pa0-f46.google.com ([209.85.220.46]:41656 "EHLO mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754985Ab2KUPKK (ORCPT ); Wed, 21 Nov 2012 10:10:10 -0500 From: Jiang Liu To: Andrew Morton , Wen Congyang , David Rientjes Cc: Jiang Liu , Maciej Rutecki , Chris Clayton , "Rafael J . Wysocki" , Mel Gorman , Minchan Kim , KAMEZAWA Hiroyuki , Michal Hocko , Jianguo Wu , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [RFT PATCH v2 4/5] mm: provide more accurate estimation of pages occupied by memmap Date: Wed, 21 Nov 2012 23:09:46 +0800 Message-Id: <1353510586-6393-1-git-send-email-jiang.liu@huawei.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <20121120111942.c9596d3f.akpm@linux-foundation.org> References: <20121120111942.c9596d3f.akpm@linux-foundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2583 Lines: 72 If SPARSEMEM is enabled, it won't build page structures for non-existing pages (holes) within a zone, so provide a more accurate estimation of pages occupied by memmap if there are bigger holes within the zone. And pages for highmem zones' memmap will be allocated from lowmem, so charge nr_kernel_pages for that. Signed-off-by: Jiang Liu --- mm/page_alloc.c | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index fc10071..9bbac97 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4442,6 +4442,26 @@ void __init set_pageblock_order(void) #endif /* CONFIG_HUGETLB_PAGE_SIZE_VARIABLE */ +static unsigned long calc_memmap_size(unsigned long spanned_pages, + unsigned long present_pages) +{ + unsigned long pages = spanned_pages; + + /* + * Provide a more accurate estimation if there are holes within + * the zone and SPARSEMEM is in use. If there are holes within the + * zone, each populated memory region may cost us one or two extra + * memmap pages due to alignment because memmap pages for each + * populated regions may not naturally algined on page boundary. + * So the (present_pages >> 4) heuristic is a tradeoff for that. + */ + if (spanned_pages > present_pages + (present_pages >> 4) && + IS_ENABLED(CONFIG_SPARSEMEM)) + pages = present_pages; + + return PAGE_ALIGN(pages * sizeof(struct page)) >> PAGE_SHIFT; +} + /* * Set up the zone data structures: * - mark all pages reserved @@ -4476,8 +4496,7 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat, * is used by this zone for memmap. This affects the watermark * and per-cpu initialisations */ - memmap_pages = - PAGE_ALIGN(size * sizeof(struct page)) >> PAGE_SHIFT; + memmap_pages = calc_memmap_size(size, realsize); if (freesize >= memmap_pages) { freesize -= memmap_pages; if (memmap_pages) @@ -4498,6 +4517,9 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat, if (!is_highmem_idx(j)) nr_kernel_pages += freesize; + /* Charge for highmem memmap if there are enough kernel pages */ + else if (nr_kernel_pages > memmap_pages * 2) + nr_kernel_pages -= memmap_pages; nr_all_pages += freesize; zone->spanned_pages = size; -- 1.7.9.5 -- 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/