From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f72.google.com (mail-wm0-f72.google.com [74.125.82.72]) by kanga.kvack.org (Postfix) with ESMTP id BA8296B0005 for ; Thu, 11 Aug 2016 05:53:21 -0400 (EDT) Received: by mail-wm0-f72.google.com with SMTP id l4so2444284wml.0 for ; Thu, 11 Aug 2016 02:53:21 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id k10si2204239wmh.11.2016.08.11.02.53.20 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 11 Aug 2016 02:53:20 -0700 (PDT) Subject: Re: [PATCH 2/5] mm/debug_pagealloc: don't allocate page_ext if we don't use guard page References: <1470809784-11516-1-git-send-email-iamjoonsoo.kim@lge.com> <1470809784-11516-3-git-send-email-iamjoonsoo.kim@lge.com> From: Vlastimil Babka Message-ID: <7391d520-0512-231b-ef2d-600ab22bda5b@suse.cz> Date: Thu, 11 Aug 2016 11:53:18 +0200 MIME-Version: 1.0 In-Reply-To: <1470809784-11516-3-git-send-email-iamjoonsoo.kim@lge.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: js1304@gmail.com, Andrew Morton Cc: Minchan Kim , Michal Hocko , Sergey Senozhatsky , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Joonsoo Kim On 08/10/2016 08:16 AM, js1304@gmail.com wrote: > From: Joonsoo Kim > > What debug_pagealloc does is just mapping/unmapping page table. > Basically, it doesn't need additional memory space to memorize something. > But, with guard page feature, it requires additional memory to distinguish > if the page is for guard or not. Guard page is only used when > debug_guardpage_minorder is non-zero so this patch removes additional > memory allocation (page_ext) if debug_guardpage_minorder is zero. > > It saves memory if we just use debug_pagealloc and not guard page. We could also save cycles with a static key for _debug_guardpage_enabled :) But memory savings are likely more significant, so > Signed-off-by: Joonsoo Kim Acked-by: Vlastimil Babka -- 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