From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f48.google.com (mail-wg0-f48.google.com [74.125.82.48]) by kanga.kvack.org (Postfix) with ESMTP id 38A766B0036 for ; Sun, 17 Aug 2014 23:22:52 -0400 (EDT) Received: by mail-wg0-f48.google.com with SMTP id x13so4358901wgg.19 for ; Sun, 17 Aug 2014 20:22:51 -0700 (PDT) Received: from szxga03-in.huawei.com (szxga03-in.huawei.com. [119.145.14.66]) by mx.google.com with ESMTPS id v1si14701883wiw.43.2014.08.17.20.22.43 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Sun, 17 Aug 2014 20:22:50 -0700 (PDT) Message-ID: <53F17068.5000005@huawei.com> Date: Mon, 18 Aug 2014 11:18:00 +0800 From: Xishi Qiu MIME-Version: 1.0 Subject: Re: [PATCH] mem-hotplug: let memblock skip the hotpluggable memory regions in __next_mem_range() References: <53E8C5AA.5040506@huawei.com> <20140816130456.GH9305@htj.dyndns.org> <53EF6C79.3000603@huawei.com> <20140817110821.GM9305@htj.dyndns.org> <53F15330.5070606@cn.fujitsu.com> In-Reply-To: <53F15330.5070606@cn.fujitsu.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: tangchen Cc: Tejun Heo , Andrew Morton , Zhang Yanfei , Wen Congyang , "H. Peter Anvin" , Linux MM , LKML On 2014/8/18 9:13, tangchen wrote: > Hi tj, > > On 08/17/2014 07:08 PM, Tejun Heo wrote: >> Hello, >> >> On Sat, Aug 16, 2014 at 10:36:41PM +0800, Xishi Qiu wrote: >>> numa_clear_node_hotplug()? There is only numa_clear_kernel_node_hotplug(). >> Yeah, that one. >> >>> If we don't clear hotpluggable flag in free_low_memory_core_early(), the >>> memory which marked hotpluggable flag will not free to buddy allocator. >>> Because __next_mem_range() will skip them. >>> >>> free_low_memory_core_early >>> for_each_free_mem_range >>> for_each_mem_range >>> __next_mem_range >> Ah, okay, so the patch fixes __next_mem_range() and thus makes >> free_low_memory_core_early() to skip hotpluggable regions unlike >> before. Please explain things like that in the changelog. Also, >> what's its relationship with numa_clear_kernel_node_hotplug()? Do we >> still need them? If so, what are the different roles that these two >> separate places serve? > > numa_clear_kernel_node_hotplug() only clears hotplug flags for the nodes > the kernel resides in, not for hotpluggable nodes. The reason why we did > this is to enable the kernel to allocate memory in case all the nodes are > hotpluggable. > Hi TangChen, I find a problem in numa_init() (arch/x86/mm/numa.c) numa_init() ... ret = init_func(); // this will mark hotpluggable flag from SRAT ... memblock_set_bottom_up(false); ... ret = numa_register_memblks(&numa_meminfo); // this will alloc node data(pglist_data) ... numa_clear_kernel_node_hotplug(); // in case all the nodes are hotpluggable ... If all the nodes are marked hotpluggable flag, alloc node data will fail. Because __next_mem_range_rev() will skip the hotpluggable memory regions. numa_register_memblks() setup_node_data() memblock_find_in_range_node() __memblock_find_range_top_down() for_each_mem_range_rev() __next_mem_range_rev() What do you think? How about move numa_clear_kernel_node_hotplug() into numa_register_memblks(), like this: numa_register_memblks() ... memblock_set_node(mb->start, mb->end - mb->start, &memblock.reserved, mb->nid); } + numa_clear_kernel_node_hotplug(); /* * If sections array is gonna be used for pfn -> nid mapping, check ... Thanks, Xishi Qiu > And we clear hotplug flags for all the nodes in free_low_memory_core_early() > is because if we do not, all hotpluggable memory won't be able to be freed > to buddy after Qiu's patch. > > 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