From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f69.google.com (mail-pg0-f69.google.com [74.125.83.69]) by kanga.kvack.org (Postfix) with ESMTP id CCFF64403E0 for ; Wed, 8 Nov 2017 02:47:55 -0500 (EST) Received: by mail-pg0-f69.google.com with SMTP id s75so1804902pgs.12 for ; Tue, 07 Nov 2017 23:47:55 -0800 (PST) Received: from lgeamrelo13.lge.com (LGEAMRELO13.lge.com. [156.147.23.53]) by mx.google.com with ESMTP id f2si3226211plk.121.2017.11.07.23.47.54 for ; Tue, 07 Nov 2017 23:47:54 -0800 (PST) Date: Wed, 8 Nov 2017 16:52:42 +0900 From: Joonsoo Kim Subject: Re: [PATCH] mm: page_ext: allocate page extension though first PFN is invalid Message-ID: <20171108075242.GB18747@js1304-P5Q-DELUXE> References: <20171107094447.14763-1-jaewon31.kim@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171107094447.14763-1-jaewon31.kim@samsung.com> Sender: owner-linux-mm@kvack.org List-ID: To: Jaewon Kim Cc: akpm@linux-foundation.org, mhocko@suse.com, vbabka@suse.cz, minchan@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, jaewon31.kim@gmail.com On Tue, Nov 07, 2017 at 06:44:47PM +0900, Jaewon Kim wrote: > online_page_ext and page_ext_init allocate page_ext for each section, but > they do not allocate if the first PFN is !pfn_present(pfn) or > !pfn_valid(pfn). > > Though the first page is not valid, page_ext could be useful for other > pages in the section. But checking all PFNs in a section may be time > consuming job. Let's check each (section count / 16) PFN, then prepare > page_ext if any PFN is present or valid. I guess that this kind of section is not so many. And, this is for debugging so completeness would be important. It's better to check all pfn in the section. Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org