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[79.224.253.90]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4587272b405sm22756835e9.19.2025.07.25.00.04.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 25 Jul 2025 00:04:10 -0700 (PDT) Message-ID: Date: Fri, 25 Jul 2025 09:04:09 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH] mm/page_alloc: Add PCP list for THP CMA To: "akash.tyagi" Cc: akpm@linux-foundation.org, vbabka@suse.cz, matthias.bgg@gmail.com, angelogioacchino.delregno@collabora.com, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, wsd_upstream@mediatek.com, chinwen.chang@mediatek.com References: <67a54f31-e568-427a-8fc8-9791fd34e11b@redhat.com> <20250725050810.1164957-1-akash.tyagi@mediatek.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAmgsLPQFCRvGjuMACgkQTd4Q 9wD/g1o0bxAAqYC7gTyGj5rZwvy1VesF6YoQncH0yI79lvXUYOX+Nngko4v4dTlOQvrd/vhb 02e9FtpA1CxgwdgIPFKIuXvdSyXAp0xXuIuRPQYbgNriQFkaBlHe9mSf8O09J3SCVa/5ezKM OLW/OONSV/Fr2VI1wxAYj3/Rb+U6rpzqIQ3Uh/5Rjmla6pTl7Z9/o1zKlVOX1SxVGSrlXhqt kwdbjdj/csSzoAbUF/duDuhyEl11/xStm/lBMzVuf3ZhV5SSgLAflLBo4l6mR5RolpPv5wad GpYS/hm7HsmEA0PBAPNb5DvZQ7vNaX23FlgylSXyv72UVsObHsu6pT4sfoxvJ5nJxvzGi69U s1uryvlAfS6E+D5ULrV35taTwSpcBAh0/RqRbV0mTc57vvAoXofBDcs3Z30IReFS34QSpjvl Hxbe7itHGuuhEVM1qmq2U72ezOQ7MzADbwCtn+yGeISQqeFn9QMAZVAkXsc9Wp0SW/WQKb76 FkSRalBZcc2vXM0VqhFVzTb6iNqYXqVKyuPKwhBunhTt6XnIfhpRgqveCPNIasSX05VQR6/a OBHZX3seTikp7A1z9iZIsdtJxB88dGkpeMj6qJ5RLzUsPUVPodEcz1B5aTEbYK6428H8MeLq NFPwmknOlDzQNC6RND8Ez7YEhzqvw7263MojcmmPcLelYbfOwU0EVcufkQEQAOfX3n0g0fZz 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+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCaCwtJQUJG8aPFAAKCRBN3hD3AP+DWlDnD/4k2TW+HyOOOePVm23F5HOhNNd7nNv3 Vq2cLcW1DteHUdxMO0X+zqrKDHI5hgnE/E2QH9jyV8mB8l/ndElobciaJcbl1cM43vVzPIWn 01vW62oxUNtEvzLLxGLPTrnMxWdZgxr7ACCWKUnMGE2E8eca0cT2pnIJoQRz242xqe/nYxBB /BAK+dsxHIfcQzl88G83oaO7vb7s/cWMYRKOg+WIgp0MJ8DO2IU5JmUtyJB+V3YzzM4cMic3 bNn8nHjTWw/9+QQ5vg3TXHZ5XMu9mtfw2La3bHJ6AybL0DvEkdGxk6YHqJVEukciLMWDWqQQ RtbBhqcprgUxipNvdn9KwNpGciM+hNtM9kf9gt0fjv79l/FiSw6KbCPX9b636GzgNy0Ev2UV m00EtcpRXXMlEpbP4V947ufWVK2Mz7RFUfU4+ETDd1scMQDHzrXItryHLZWhopPI4Z+ps0rB CQHfSpl+wG4XbJJu1D8/Ww3FsO42TMFrNr2/cmqwuUZ0a0uxrpkNYrsGjkEu7a+9MheyTzcm vyU2knz5/stkTN2LKz5REqOe24oRnypjpAfaoxRYXs+F8wml519InWlwCra49IUSxD1hXPxO WBe5lqcozu9LpNDH/brVSzHCSb7vjNGvvSVESDuoiHK8gNlf0v+epy5WYd7CGAgODPvDShGN g3eXuA== Organization: Red Hat In-Reply-To: <20250725050810.1164957-1-akash.tyagi@mediatek.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: P41dUorDluRzhL7sru7kJb7hlwt8rPxl5a9KlzcWXrM_1753427052 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: A2BAA40009 X-Rspamd-Server: rspam06 X-Stat-Signature: jwcmu8umjf4q9f87kwdxaaiwt9xan93z X-HE-Tag: 1753427055-505600 X-HE-Meta: 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 XrqbpWUu 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 25.07.25 07:08, akash.tyagi wrote: > Hi David, > > Thank you for your feedback. > > We encountered this issue in the Android Common Kernel (version 6.12), which uses PCP lists for CMA pages. > > page_owner trace- > Page allocated via order 9, mask 0x52dc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_ZERO), pid 1, tgid 1 (swapper/0), ts 1065952310 ns > PFN 0x23d200 type Unmovable Block 4585 type CMA Flags 0x4000000000000040(head|zone=1|kasantag=0x0) > post_alloc_hook+0x228/0x230 > prep_new_page+0x28/0x148 > get_page_from_freelist+0x19d0/0x1a38 > __alloc_pages_noprof+0x1b0/0x440 > ___kmalloc_large_node+0xb4/0x1ec > __kmalloc_large_node_noprof+0x2c/0xec > __kmalloc_node_noprof+0x39c/0x548 > __kvmalloc_node_noprof+0xd8/0x18c > nf_ct_alloc_hashtable+0x64/0x108 > nf_nat_init+0x3c/0xf8 > do_one_initcall+0x150/0x3c0 > do_initcall_level+0xa4/0x15c > do_initcalls+0x70/0xc0 > do_basic_setup+0x1c/0x28 > kernel_init_freeable+0xcc/0x130 > kernel_init+0x20/0x1ac > > This UNMOVABLE page was allocated from CMA, but it could not be migrated - so CMA alloc failed > At first, we fixed this by adding CMA THP pages to the movable THP PCP list. > This fixed the issue of CMA pages being put in the wrong list, but now any movable allocation can use these CMA pages. > > Later, we saw that a movable allocation used a CMA page and was pinned by __filemap_get_folio(). This page was pinned for too long, and eventually, CMA allocation failed > > page_owner trace- > Page allocated via order 0, mask 0x140c48(GFP_NOFS|__GFP_COMP|__GFP_HARDWALL|__GFP_MOVABLE), pid 1198, tgid 1194 (ccci_mdinit), ts 17918751965 ns > PFN 0x207233 type Movable Block 4153 type CMA Flags 0x4020000000008224(referenced|lru|workingset|private|zone=1|kasantag=0x0) > post_alloc_hook+0x23c/0x254 > prep_new_page+0x28/0x148 > get_page_from_freelist+0x19d8/0x1a40 > __alloc_pages_noprof+0x1a8/0x430 > __folio_alloc_noprof+0x14/0x5c > __filemap_get_folio+0x1bc/0x430 > bdev_getblk+0xd4/0x294 > __read_extent_tree_block+0x6c/0x260 > ext4_find_extent+0x22c/0x3dc > ext4_ext_map_blocks+0x88/0x173c > ext4_map_query_blocks+0x54/0xe0 > ext4_map_blocks+0xf8/0x518 > _ext4_get_block+0x70/0x188 > ext4_get_block+0x18/0x24 > ext4_block_write_begin+0x154/0x62c > ext4_write_begin+0x20c/0x630 > Page has been migrated, last migrate reason: compaction > Charged to memcg / > > > Currently, free_unref_page treats CMA pages as movable. So, some MOVABLE allocations may use these CMA pages and pinned them. Later, when CMA needs these pages, these pages failed to migrate. MOVABLE allocations commonly fallback to CMA allocations, independent of pcp. Long-term pinning is forbidden on MIGRATE_CMA pages. We had a bug recently fixed, maybe you ran into that? See commit 517f496e1e61bd169d585dab4dd77e7147506322 Author: David Hildenbrand Date: Wed Jun 11 15:13:14 2025 +0200 mm/gup: revert "mm: gup: fix infinite loop within __get_longterm_locked" After commit 1aaf8c122918 ("mm: gup: fix infinite loop within __get_longterm_locked") we are able to longterm pin folios that are not supposed to get longterm pinned, simply because they temporarily have the LRU flag cleared (esp. temporarily isolated). For example, two __get_longterm_locked() callers can race, or __get_longterm_locked() can race with anything else that temporarily isolates folios. But there is this known problem that CMA can fail temporarily due to short-term pinnings. See the "reliable CMA" work (don't remember the exact name). So what you proposed in the patch at least does not apply I think. -- Cheers, David / dhildenb