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Tue, 14 Jan 2020 08:30:23 +0000 (UTC) Received: from [10.36.117.154] (ovpn-117-154.ams2.redhat.com [10.36.117.154]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7586C5DA70; Tue, 14 Jan 2020 08:30:20 +0000 (UTC) Subject: Re: [PATCH] mm/page_alloc: Add a reason for reserved pages in has_unmovable_pages() To: Anshuman Khandual , Qian Cai Cc: linux-mm@kvack.org, Andrew Morton , Michal Hocko , Vlastimil Babka , Oscar Salvador , Mel Gorman , Mike Rapoport , Dan Williams , Pavel Tatashin , linux-kernel@vger.kernel.org References: <49fa7dea-00ac-155f-e7b7-eeca206556b5@arm.com> <6A58E80B-7A5F-4CAD-ACF1-89BCCBE4D3B1@lca.pw> 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: <85c5a146-0014-16cc-0c31-9b99fc02e847@redhat.com> Date: Tue, 14 Jan 2020 09:30:19 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 14.01.20 09:19, Anshuman Khandual wrote: > > > On 10/04/2019 01:55 PM, David Hildenbrand wrote: >> On 03.10.19 14:14, Qian Cai wrote: >>> >>> >>>> On Oct 3, 2019, at 8:01 AM, Anshuman Khandual wrote: >>>> >>>> Will something like this be better ? >>> >>> Not really. dump_page() will dump PageCompound information anyway, so it is trivial to figure out if went in that path. >>> >> >> I agree, I use the dump_page() output frequently to identify PG_reserved >> pages. No need to duplicate that. > > Here in this path there is a reserved page which is preventing > offlining a memory section but unfortunately dump_page() does > not print page->flags for a reserved page pinned there possibly > through memblock_reserve() during boot. > > __offline_pages() > start_isolate_page_range() > set_migratetype_isolate() > has_unmovable_pages() > dump_page() > > [ 64.920970] ------------[ cut here ]------------ > [ 64.921718] WARNING: CPU: 16 PID: 1116 at mm/page_alloc.c:8298 has_unmovable_pages+0x274/0x2a8 > [ 64.923110] Modules linked in: > [ 64.923634] CPU: 16 PID: 1116 Comm: bash Not tainted 5.5.0-rc6-00006-gca544f2a11ae-dirty #281 > [ 64.925102] Hardware name: linux,dummy-virt (DT) > [ 64.925905] pstate: 60400085 (nZCv daIf +PAN -UAO) > [ 64.926742] pc : has_unmovable_pages+0x274/0x2a8 > [ 64.927554] lr : has_unmovable_pages+0x298/0x2a8 > [ 64.928359] sp : ffff800014fd3a00 > [ 64.928944] x29: ffff800014fd3a00 x28: fffffe0017640000 > [ 64.929875] x27: 0000000000000000 x26: ffff0005fcfcda00 > [ 64.930810] x25: 0000000000640000 x24: 0000000000000003 > [ 64.931736] x23: 0000000019840000 x22: 0000000000001380 > [ 64.932667] x21: ffff800011259000 x20: ffff0005fcfcda00 > [ 64.933588] x19: 0000000000661000 x18: 0000000000000010 > [ 64.934514] x17: 0000000000000000 x16: 0000000000000000 > [ 64.935454] x15: ffffffffffffffff x14: ffff8000118498c8 > [ 64.936377] x13: ffff800094fd3797 x12: ffff800014fd379f > [ 64.937304] x11: ffff800011861000 x10: ffff800014fd3720 > [ 64.938226] x9 : 00000000ffffffd0 x8 : ffff8000106a60d0 > [ 64.939156] x7 : 0000000000000000 x6 : ffff0005fc6261b0 > [ 64.940078] x5 : ffff0005fc6261b0 x4 : 0000000000000000 > [ 64.941003] x3 : ffff0005fc62cf80 x2 : ffffffffffffec80 > [ 64.941927] x1 : ffff800011141b58 x0 : ffff0005fcfcda00 > [ 64.942857] Call trace: > [ 64.943298] has_unmovable_pages+0x274/0x2a8 > [ 64.944056] start_isolate_page_range+0x258/0x360 > [ 64.944879] __offline_pages+0xf4/0x9e8 > [ 64.945554] offline_pages+0x10/0x18 > [ 64.946189] memory_block_action+0x40/0x1a0 > [ 64.946929] memory_subsys_offline+0x4c/0x78 > [ 64.947679] device_offline+0x98/0xc8 > [ 64.948328] unprobe_store+0xa8/0x158 > [ 64.948976] dev_attr_store+0x14/0x28 > [ 64.949628] sysfs_kf_write+0x40/0x50 > [ 64.950273] kernfs_fop_write+0x108/0x218 > [ 64.950983] __vfs_write+0x18/0x40 > [ 64.951592] vfs_write+0xb0/0x1d0 > [ 64.952175] ksys_write+0x64/0xe8 > [ 64.952761] __arm64_sys_write+0x18/0x20 > [ 64.953451] el0_svc_common.constprop.2+0x88/0x150 > [ 64.954293] el0_svc_handler+0x20/0x80 > [ 64.954963] el0_sync_handler+0x118/0x188 > [ 64.955669] el0_sync+0x140/0x180 > [ 64.956256] ---[ end trace b162b4d1cbea304d ]--- > [ 64.957063] page:fffffe0017640000 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 > [ 64.958489] raw: 1ffff80000001000 fffffe0017640008 fffffe0017640008 0000000000000000 > [ 64.959839] raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000 > [ 64.961174] page dumped because: unmovable page > > The reason is dump_page() does not print page->flags universally > and only does so for KSM, Anon and File pages while excluding > reserved pages at boot. Wondering should not we make printing > page->flags universal ? The thing is that "PageReserved" on a random page tells us that the values in the memmap cannot be trusted (in some scenarios). However, we also expose flags for reserved pages via stable_page_flags() - /proc/kpageflags. As this is just a debugging mechanism, I think it makes sense to also print them. -- Thanks, David / dhildenb