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Tue, 26 May 2020 11:49:39 +0000 (UTC) Received: from [10.36.114.130] (ovpn-114-130.ams2.redhat.com [10.36.114.130]) by smtp.corp.redhat.com (Postfix) with ESMTP id A188160CCC; Tue, 26 May 2020 11:49:37 +0000 (UTC) Subject: Re: [PATCH] mm/compaction: Fix the incorrect hole in fast_isolate_freepages() To: Mike Rapoport , Baoquan He Cc: mgorman@suse.de, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, cai@lca.pw, mhocko@kernel.org References: <20200521014407.29690-1-bhe@redhat.com> <20200521092612.GP1059226@linux.ibm.com> <20200521155225.GA20045@MiWiFi-R3L-srv> <20200521171836.GU1059226@linux.ibm.com> <20200522070114.GE26955@MiWiFi-R3L-srv> <20200522072524.GF26955@MiWiFi-R3L-srv> <20200522142053.GW1059226@linux.ibm.com> <20200526084543.GG26955@MiWiFi-R3L-srv> <20200526113244.GH13212@linux.ibm.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMFCQlmAYAGCwkIBwMCBhUI AgkKCwQWAgMBAh4BAheAFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl3pImkCGQEACgkQTd4Q 9wD/g1o+VA//SFvIHUAvul05u6wKv/pIR6aICPdpF9EIgEU448g+7FfDgQwcEny1pbEzAmiw zAXIQ9H0NZh96lcq+yDLtONnXk/bEYWHHUA014A1wqcYNRY8RvY1+eVHb0uu0KYQoXkzvu+s Dncuguk470XPnscL27hs8PgOP6QjG4jt75K2LfZ0eAqTOUCZTJxA8A7E9+XTYuU0hs7QVrWJ jQdFxQbRMrYz7uP8KmTK9/Cnvqehgl4EzyRaZppshruKMeyheBgvgJd5On1wWq4ZUV5PFM4x II3QbD3EJfWbaJMR55jI9dMFa+vK7MFz3rhWOkEx/QR959lfdRSTXdxs8V3zDvChcmRVGN8U Vo93d1YNtWnA9w6oCW1dnDZ4kgQZZSBIjp6iHcA08apzh7DPi08jL7M9UQByeYGr8KuR4i6e RZI6xhlZerUScVzn35ONwOC91VdYiQgjemiVLq1WDDZ3B7DIzUZ4RQTOaIWdtXBWb8zWakt/ ztGhsx0e39Gvt3391O1PgcA7ilhvqrBPemJrlb9xSPPRbaNAW39P8ws/UJnzSJqnHMVxbRZC Am4add/SM+OCP0w3xYss1jy9T+XdZa0lhUvJfLy7tNcjVG/sxkBXOaSC24MFPuwnoC9WvCVQ ZBxouph3kqc4Dt5X1EeXVLeba+466P1fe1rC8MbcwDkoUo65Ag0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAGJAiUEGAECAA8FAlXLn5ECGwwFCQlmAYAACgkQTd4Q 9wD/g1qA6w/+M+ggFv+JdVsz5+ZIc6MSyGUozASX+bmIuPeIecc9UsFRatc91LuJCKMkD9Uv GOcWSeFpLrSGRQ1Z7EMzFVU//qVs6uzhsNk0RYMyS0B6oloW3FpyQ+zOVylFWQCzoyyf227y GW8HnXunJSC+4PtlL2AY4yZjAVAPLK2l6mhgClVXTQ/S7cBoTQKP+jvVJOoYkpnFxWE9pn4t H5QIFk7Ip8TKr5k3fXVWk4lnUi9MTF/5L/mWqdyIO1s7cjharQCstfWCzWrVeVctpVoDfJWp 4LwTuQ5yEM2KcPeElLg5fR7WB2zH97oI6/Ko2DlovmfQqXh9xWozQt0iGy5tWzh6I0JrlcxJ ileZWLccC4XKD1037Hy2FLAjzfoWgwBLA6ULu0exOOdIa58H4PsXtkFPrUF980EEibUp0zFz GotRVekFAceUaRvAj7dh76cToeZkfsjAvBVb4COXuhgX6N4pofgNkW2AtgYu1nUsPAo+NftU CxrhjHtLn4QEBpkbErnXQyMjHpIatlYGutVMS91XTQXYydCh5crMPs7hYVsvnmGHIaB9ZMfB njnuI31KBiLUks+paRkHQlFcgS2N3gkRBzH7xSZ+t7Re3jvXdXEzKBbQ+dC3lpJB0wPnyMcX FOTT3aZT7IgePkt5iC/BKBk3hqKteTnJFeVIT7EC+a6YUFg= Organization: Red Hat GmbH Message-ID: <01beec81-565f-d335-5eff-22693fc09c0e@redhat.com> Date: Tue, 26 May 2020 13:49:36 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200526113244.GH13212@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 26.05.20 13:32, Mike Rapoport wrote: > Hello Baoquan, > > On Tue, May 26, 2020 at 04:45:43PM +0800, Baoquan He wrote: >> On 05/22/20 at 05:20pm, Mike Rapoport wrote: >>> Hello Baoquan, >>> >>> On Fri, May 22, 2020 at 03:25:24PM +0800, Baoquan He wrote: >>>> On 05/22/20 at 03:01pm, Baoquan He wrote: >>>>> >>>>> So let's add these unavailable ranges into memblock and reserve them >>>>> in init_unavailable_range() instead. With this change, they will be added >>>>> into appropriate node and zone in memmap_init(), and initialized in >>>>> reserve_bootmem_region() just like any other memblock reserved regions. >>>> >>>> Seems this is not right. They can't get nid in init_unavailable_range(). >>>> Adding e820 ranges may let them get nid. But the hole range won't be >>>> added to memblock, and still has the issue. >>>> >>>> Nack this one for now, still considering. >>> >>> Why won't we add the e820 reserved ranges to memblock.memory during >>> early boot as I suggested? >>> >>> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c >>> index c5399e80c59c..b0940c618ed9 100644 >>> --- a/arch/x86/kernel/e820.c >>> +++ b/arch/x86/kernel/e820.c >>> @@ -1301,8 +1301,11 @@ void __init e820__memblock_setup(void) >>> if (end != (resource_size_t)end) >>> continue; >>> >>> - if (entry->type == E820_TYPE_SOFT_RESERVED) >>> + if (entry->type == E820_TYPE_SOFT_RESERVED || >>> + entry->type == E820_TYPE_RESERVED) { >>> + memblock_add(entry->addr, entry->size); >>> memblock_reserve(entry->addr, entry->size); >>> + } >>> >>> if (entry->type != E820_TYPE_RAM && entry->type != E820_TYPE_RESERVED_KERN) >>> continue; >>> >>> The setting of node later in numa_init() will assign the proper node >>> for these regions as it does for the usable memory. >> >> Yes, if it's only related to e820 reserved region, this truly works. >> >> However, it also has ACPI table regions. That's why I changed to call >> the problematic area as firmware reserved ranges later. >> >> Bisides, you can see below line, there's another reserved region which only >> occupies one page in one memory seciton. If adding to memblock.memory, we also >> will build struct mem_section and the relevant struct pages for the whole >> section. And then the holes around that page will be added and initialized in >> init_unavailable_mem(). numa_init() will assign proper node for memblock.memory >> and memblock.reserved, but won't assign proper node for the holes. >> >> ~~~ >> [ 0.000000] BIOS-e820: [mem 0x00000000fed80000-0x00000000fed80fff] reserved >> ~~~ >> >> So I still think we should not add firmware reserved range into >> memblock for fixing this issue. >> >> And, the fix in the original patch seems necessary. You can see in >> compaction code, the migration source is chosen from LRU pages or >> movable pages, the migration target has to be got from Buddy. However, >> only the min_pfn in fast_isolate_freepages(), it's calculated by >> distance between cc->free_pfn - cc->migrate_pfn, we can't guarantee it's >> safe, then use it as the target to handle. > > I do not object to your original fix with careful check for pfn validity. > > But I still think that the memory reserved by the firmware is still > memory and it should be added to memblock.memory. This way the memory If it's really memory that could be read/written, I think I agree. > map will be properly initialized from the very beginning and we won't > need init_unavailable_mem() and alike workarounds and. Obviously, the patch I remember init_unavailable_mem() is necessary for holes within sections, where we actually *don't* have memory, but we still have have a valid memmap (full section) that we have to initialize. See the example from 4b094b7851bf ("mm/page_alloc.c: initialize memmap of unavailable memory directly"). Our main memory ends within a section, so we have to initialize the remaining parts because the whole section will be marked valid/online. Any way to improve this handling is appreciated. In that patch I also spelled out that we might want to mark such holes via a new page type, e.g., PageHole(). Such a page is a memory hole, but has a valid memmap. Any content in the memmap (zone/node) should be ignored. But it's all quite confusing, especially across architectures and ... > above is not enough, but it's a small step in this direction. > > I believe that improving the early memory initialization would make many > things simpler and more robust, but that's a different story :) ... I second that. -- Thanks, David / dhildenb