Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932485Ab2K1XwY (ORCPT ); Wed, 28 Nov 2012 18:52:24 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:60948 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932351Ab2K1XwX (ORCPT ); Wed, 28 Nov 2012 18:52:23 -0500 Date: Wed, 28 Nov 2012 15:52:21 -0800 From: Andrew Morton To: Jiang Liu Cc: Wen Congyang , David Rientjes , 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: Re: [RFT PATCH v2 4/5] mm: provide more accurate estimation of pages occupied by memmap Message-Id: <20121128155221.df369ce4.akpm@linux-foundation.org> In-Reply-To: <1353510586-6393-1-git-send-email-jiang.liu@huawei.com> References: <20121120111942.c9596d3f.akpm@linux-foundation.org> <1353510586-6393-1-git-send-email-jiang.liu@huawei.com> X-Mailer: Sylpheed 3.0.2 (GTK+ 2.20.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2396 Lines: 66 On Wed, 21 Nov 2012 23:09:46 +0800 Jiang Liu wrote: > Subject: Re: [RFT PATCH v2 4/5] mm: provide more accurate estimation of pages occupied by memmap How are people to test this? "does it boot"? > 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. > > ... > > --- 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; > +} > + I spose we should do this, although it makes no difference as the compiler will inline calc_memmap_size() into its caller: --- a/mm/page_alloc.c~mm-provide-more-accurate-estimation-of-pages-occupied-by-memmap-fix +++ a/mm/page_alloc.c @@ -4526,8 +4526,8 @@ 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) +static unsigned long __paginginit calc_memmap_size(unsigned long spanned_pages, + unsigned long present_pages) { unsigned long pages = spanned_pages; -- 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/