From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yh0-f41.google.com (mail-yh0-f41.google.com [209.85.213.41]) by kanga.kvack.org (Postfix) with ESMTP id 05BD86B0038 for ; Mon, 20 Apr 2015 14:23:50 -0400 (EDT) Received: by yhla23 with SMTP id a23so18442813yhl.1 for ; Mon, 20 Apr 2015 11:23:49 -0700 (PDT) Received: from mail-yh0-x22e.google.com (mail-yh0-x22e.google.com. [2607:f8b0:4002:c01::22e]) by mx.google.com with ESMTPS id a142si10760227yka.128.2015.04.20.11.23.49 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 20 Apr 2015 11:23:49 -0700 (PDT) Received: by yhrr66 with SMTP id r66so5523407yhr.3 for ; Mon, 20 Apr 2015 11:23:49 -0700 (PDT) Message-ID: <55354434.2902ec0a.14ab.fffffff6@mx.google.com> Date: Mon, 20 Apr 2015 11:23:48 -0700 (PDT) From: Yasuaki Ishimatsu Subject: Re: [PATCH 1/2 V2] memory-hotplug: fix BUG_ON in move_freepages() In-Reply-To: <55347592.4050400@huawei.com> References: <5530E578.9070505@huawei.com> <5531679d.4642ec0a.1beb.3569@mx.google.com> <55345979.2020502@cn.fujitsu.com> <55346859.30605@huawei.com> <553472b0.4ad2ec0a.3abe.ffffd0f6@mx.google.com> <55347592.4050400@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Xishi Qiu Cc: Gu Zheng , Andrew Morton , Yasuaki Ishimatsu , Kamezawa Hiroyuki , izumi.taku@jp.fujitsu.com, Tang Chen , Xiexiuqi , Mel Gorman , David Rientjes , Linux MM , LKML On Mon, 20 Apr 2015 11:42:10 +0800 Xishi Qiu wrote: > On 2015/4/20 11:29, Yasuaki Ishimatsu wrote: > > > > > On Mon, 20 Apr 2015 10:45:45 +0800 > > Xishi Qiu wrote: > > > >> On 2015/4/20 9:42, Gu Zheng wrote: > >> > >>> Hi Xishi, > >>> On 04/18/2015 04:05 AM, Yasuaki Ishimatsu wrote: > >>> > >>>> > >>>> Your patches will fix your issue. > >>>> But, if BIOS reports memory first at node hot add, pgdat can > >>>> not be initialized. > >>>> > >>>> Memory hot add flows are as follows: > >>>> > >>>> add_memory > >>>> ... > >>>> -> hotadd_new_pgdat() > >>>> ... > >>>> -> node_set_online(nid) > >>>> > >>>> When calling hotadd_new_pgdat() for a hot added node, the node is > >>>> offline because node_set_online() is not called yet. So if applying > >>>> your patches, the pgdat is not initialized in this case. > >>> > >>> Ishimtasu's worry is reasonable. And I am afraid the fix here is a bit > >>> over-kill. > >>> > >>>> > >>>> Thanks, > >>>> Yasuaki Ishimatsu > >>>> > >>>> On Fri, 17 Apr 2015 18:50:32 +0800 > >>>> Xishi Qiu wrote: > >>>> > >>>>> Hot remove nodeXX, then hot add nodeXX. If BIOS report cpu first, it will call > >>>>> hotadd_new_pgdat(nid, 0), this will set pgdat->node_start_pfn to 0. As nodeXX > >>>>> exists at boot time, so pgdat->node_spanned_pages is the same as original. Then > >>>>> free_area_init_core()->memmap_init() will pass a wrong start and a nonzero size. > >>> > >>> As your analysis said the root cause here is passing a *0* as the node_start_pfn, > >>> then the chaos occurred when init the zones. And this only happens to the re-hotadd > >>> node, so how about using the saved *node_start_pfn* (via get_pfn_range_for_nid(nid, &start_pfn, &end_pfn)) > >>> instead if we find "pgdat->node_start_pfn == 0 && !node_online(XXX)"? > >>> > >>> Thanks, > >>> Gu > >>> > >> > >> Hi Gu, > >> > >> I first considered this method, but if the hot added node's start and size are different > >> from before, it makes the chaos. > >> > > > >> e.g. > >> nodeXX (8-16G) > >> remove nodeXX > >> BIOS report cpu first and online it > >> hotadd nodeXX > >> use the original value, so pgdat->node_start_pfn is set to 8G, and size is 8G > >> BIOS report mem(10-12G) > >> call add_memory()->__add_zone()->grow_zone_span()/grow_pgdat_span() > >> the start is still 8G, not 10G, this is chaos! > > > > If you set CONFIG_HAVE_MEMBLOCK_NODE_MAP, kernel shows the following > > pr_info()'s message. > > > > void __paginginit free_area_init_node(int nid, unsigned long *zones_size, > > unsigned long node_start_pfn, unsigned long *zholes_size) > > { > > ... > > #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP > > get_pfn_range_for_nid(nid, &start_pfn, &end_pfn); > > pr_info("Initmem setup node %d [mem %#018Lx-%#018Lx]\n", nid, > > (u64)start_pfn << PAGE_SHIFT, ((u64)end_pfn << PAGE_SHIFT) - 1); > > #endif > > } > > > > Is the memory range of the message "8G - 16G"? > > If so, the reason is that memblk is not deleted at memory hot remove. > > > > Thanks, > > Yasuaki Ishimatsu > > > > Hi Yasuaki, > > By reading the code, I find memblk is not deleted at memory hot remove. > I am not sure whether we should remove it. If remove it, we should also reset > "arch_zone_lowest_possible_pfn", right? It seems a little complicated. I think memblk should be added/removed by hot adding/removing memory. But, arch_zone_lowest_possible_pfn should not be changed. Thanks, Yasuaki Ishimatsu > > Thanks, > Xishi Qiu > > > > > > >> > >> Thanks, > >> Xishi Qiu > >> > > > > . > > > > > -- 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