From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f48.google.com (mail-pa0-f48.google.com [209.85.220.48]) by kanga.kvack.org (Postfix) with ESMTP id 226686B0255 for ; Fri, 9 Oct 2015 06:36:49 -0400 (EDT) Received: by pablk4 with SMTP id lk4so83719173pab.3 for ; Fri, 09 Oct 2015 03:36:48 -0700 (PDT) Received: from szxga03-in.huawei.com ([119.145.14.66]) by mx.google.com with ESMTPS id mk6si1609046pab.21.2015.10.09.03.36.46 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Fri, 09 Oct 2015 03:36:48 -0700 (PDT) Message-ID: <5617989E.9070700@huawei.com> Date: Fri, 9 Oct 2015 18:36:14 +0800 From: Xishi Qiu MIME-Version: 1.0 Subject: Re: [PATCH][RFC] mm: Introduce kernelcore=reliable option References: <1444402599-15274-1-git-send-email-izumi.taku@jp.fujitsu.com> <561762DC.3080608@huawei.com> <561787DA.4040809@jp.fujitsu.com> In-Reply-To: <561787DA.4040809@jp.fujitsu.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Kamezawa Hiroyuki Cc: Taku Izumi , linux-kernel@vger.kernel.org, linux-mm@kvack.org, tony.luck@intel.com, mel@csn.ul.ie, akpm@linux-foundation.org, Dave Hansen , Mel Gorman , Ingo Molnar , zhongjiang@huawei.com On 2015/10/9 17:24, Kamezawa Hiroyuki wrote: > On 2015/10/09 15:46, Xishi Qiu wrote: >> On 2015/10/9 22:56, Taku Izumi wrote: >> >>> Xeon E7 v3 based systems supports Address Range Mirroring >>> and UEFI BIOS complied with UEFI spec 2.5 can notify which >>> ranges are reliable (mirrored) via EFI memory map. >>> Now Linux kernel utilize its information and allocates >>> boot time memory from reliable region. >>> >>> My requirement is: >>> - allocate kernel memory from reliable region >>> - allocate user memory from non-reliable region >>> >>> In order to meet my requirement, ZONE_MOVABLE is useful. >>> By arranging non-reliable range into ZONE_MOVABLE, >>> reliable memory is only used for kernel allocations. >>> >> >> Hi Taku, >> >> You mean set non-mirrored memory to movable zone, and set >> mirrored memory to normal zone, right? So kernel allocations >> will use mirrored memory in normal zone, and user allocations >> will use non-mirrored memory in movable zone. >> >> My question is: >> 1) do we need to change the fallback function? > > For *our* requirement, it's not required. But if someone want to prevent > user's memory allocation from NORMAL_ZONE, we need some change in zonelist > walking. > Hi Kame, So we assume kernel will only use normal zone(mirrored), and users use movable zone(non-mirrored) first if the memory is not enough, then use normal zone too. >> 2) the mirrored region should locate at the start of normal >> zone, right? > > Precisely, "not-reliable" range of memory are handled by ZONE_MOVABLE. > This patch does only that. I mean the mirrored region can not at the middle or end of the zone, BIOS should report the memory like this, e.g. BIOS node0: 0-4G mirrored, 4-8G mirrored, 8-16G non-mirrored node1: 16-24G mirrored, 24-32G non-mirrored OS node0: DMA DMA32 are both mirrored, NORMAL(4-8G), MOVABLE(8-16G) node1: NORMAL(16-24G), MOVABLE(24-32G) > >> >> I remember Kame has already suggested this idea. In my opinion, >> I still think it's better to add a new migratetype or a new zone, >> so both user and kernel could use mirrored memory. > > Hi, Xishi. > > I and Izumi-san discussed the implementation much and found using "zone" > is better approach. > > The biggest reason is that zone is a unit of vmscan and all statistics and > handling the range of memory for a purpose. We can reuse all vmscan and > information codes by making use of zones. Introdcing other structure will be messy. Yes, add a new zone is better, but it will change much code, so reuse ZONE_MOVABLE is simpler and easier, right? > His patch is very simple. > The following plan sounds good to me. Shall we rename the zone name when it is used for mirrored memory, "movable" is a little confusion. > For your requirements. I and Izumi-san are discussing following plan. > > - Add a flag to show the zone is reliable or not, then, mark ZONE_MOVABLE as not-reliable. > - Add __GFP_RELIABLE. This will allow alloc_pages() to skip not-reliable zone. > - Add madivse() MADV_RELIABLE and modify page fault code's gfp flag with that flag. > like this? user: madvise()/mmap()/or others -> add vma_reliable flag -> add gfp_reliable flag -> alloc_pages kernel: use __GFP_RELIABLE flag in buddy allocation/slab/vmalloc... Also we can introduce some interfaces in procfs or sysfs, right? Thanks, Xishi Qiu > > Thanks, > -Kame > > > > > > > > > > > > > > > > > > > > > > > . > -- 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