From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id EFB8E6B004D for ; Tue, 18 Aug 2009 02:29:41 -0400 (EDT) Message-ID: <4A8A4ABB.70003@redhat.com> Date: Tue, 18 Aug 2009 14:31:23 +0800 From: Amerigo Wang MIME-Version: 1.0 Subject: Re: [Patch 8/8] kexec: allow to shrink reserved memory References: <20090812081731.5757.25254.sendpatchset@localhost.localdomain> <20090812081906.5757.39417.sendpatchset@localhost.localdomain> <4A83893D.50707@redhat.com> <4A83CD84.8040609@redhat.com> <4A8927DD.6060209@redhat.com> <20090818092939.2efbe158.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20090818092939.2efbe158.kamezawa.hiroyu@jp.fujitsu.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: KAMEZAWA Hiroyuki Cc: "Eric W. Biederman" , linux-kernel@vger.kernel.org, tony.luck@intel.com, linux-ia64@vger.kernel.org, linux-mm@kvack.org, Neil Horman , Andi Kleen , akpm@linux-foundation.org, bernhard.walle@gmx.de, Fenghua Yu , Ingo Molnar , Anton Vorontsov List-ID: KAMEZAWA Hiroyuki wrote: > On Mon, 17 Aug 2009 17:50:21 +0800 > Amerigo Wang wrote: > > >> Eric W. Biederman wrote: >> >>> Amerigo Wang writes: >>> >>> >>> >>>> Not that simple, marking it as "__init" means it uses some "__init" data which >>>> will be dropped after initialization. >>>> >>>> >>> If we start with the assumption that we will be reserving to much and >>> will free the memory once we know how much we really need I see a very >>> simple way to go about this. We ensure that the reservation of crash >>> kernel memory is done through a normal allocation so that we have >>> struct page entries for every page. On 32bit x86 that is an extra 1MB >>> for a 128MB allocation. >>> >>> Then when it comes time to release that memory we clear whatever magic >>> flags we have on the page (like PG_reserve) and call free_page. >>> >>> >> Hmm, my MM knowledge is not good enough to judge if this works... >> I need to check more MM source code. >> >> Can any MM people help? >> >> > Hm, memory-hotplug guy is here. > Hi, thank you! > Can I have a question ? > > - How crash kernel's memory is preserved at boot ? > Use bootmem, I think. > It's hidden from the system before mem_init() ? > Not sure, but probably yes. It is reserved in setup_arch() which is before mm_init() which calls mem_init(). Do you have any advice to free that reserved memory after boot? :) 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