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[2003:cb:c737:1f00:94ff:246b:30d0:686b]) by smtp.gmail.com with ESMTPSA id p10-20020a5d638a000000b0033e206a0a7asm9318645wru.26.2024.03.18.02.48.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 18 Mar 2024 02:48:02 -0700 (PDT) Message-ID: Date: Mon, 18 Mar 2024 10:48:01 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v2] mm: support multi-size THP numa balancing To: Baolin Wang , "Huang, Ying" Cc: akpm@linux-foundation.org, mgorman@techsingularity.net, wangkefeng.wang@huawei.com, jhubbard@nvidia.com, 21cnbao@gmail.com, ryan.roberts@arm.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <903bf13fc3e68b8dc1f256570d78b55b2dd9c96f.1710493587.git.baolin.wang@linux.alibaba.com> <871q88vzc4.fsf@yhuang6-desk2.ccr.corp.intel.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/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz 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+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 1E177A0007 X-Stat-Signature: zf56ze6apzba5q1g73gz6ykcrht4kom9 X-Rspam-User: X-HE-Tag: 1710755286-868369 X-HE-Meta: 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 qzwt4Lcl t34Zmz/hc3Tg6YI7gZDucpTCpuRem1xOC16GVNVeCAh5CriRoOcfyhl8udb11/l4WCOCdWlkz/lWLxbAuZX5u/tsZfA1QBCW2DYR7tl8Ufym26ADOtFmbalvyF5nalSEmpj+EnVUH1VxD6f3GZRDUCw/iI07P3OGv37wcsjAvv1cH6I2ib9H+msmvvhjuD4PF4dt98ZqMXz7r0tCP3D/r7aLR0yjm+xc5Vegnjjg/ulWqqaGHZB3ZVYf+DZ97WKGqdCEcKqFCwth8WAcpdN4PsIOB0sRizPChydxP8V1eHHAVmeQ/HYpUE3baKNjNgJVo6ODnMetvqaS0v69USEdgYgiB1rdpZCXbWfdtDSfqg0l2sQ3KGaxpTRf9lCSXSxR6ACuVP8ho+l55GSTg7FnDLFxXTnniVrnspeHYUlKw5xyWAX0bwPkk75yTQ2nrtuHK8uNT 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 18.03.24 10:42, Baolin Wang wrote: > > > On 2024/3/18 14:16, Huang, Ying wrote: >> Baolin Wang writes: >> >>> Now the anonymous page allocation already supports multi-size THP (mTHP), >>> but the numa balancing still prohibits mTHP migration even though it is an >>> exclusive mapping, which is unreasonable. Thus let's support the exclusive >>> mTHP numa balancing firstly. >>> >>> Allow scanning mTHP: >>> Commit 859d4adc3415 ("mm: numa: do not trap faults on shared data section >>> pages") skips shared CoW pages' NUMA page migration to avoid shared data >>> segment migration. In addition, commit 80d47f5de5e3 ("mm: don't try to >>> NUMA-migrate COW pages that have other uses") change to use page_count() >>> to avoid GUP pages migration, that will also skip the mTHP numa scaning. >>> Theoretically, we can use folio_maybe_dma_pinned() to detect the GUP >>> issue, although there is still a GUP race, the issue seems to have been >>> resolved by commit 80d47f5de5e3. Meanwhile, use the folio_estimated_sharers() >>> to skip shared CoW pages though this is not a precise sharers count. To >>> check if the folio is shared, ideally we want to make sure every page is >>> mapped to the same process, but doing that seems expensive and using >>> the estimated mapcount seems can work when running autonuma benchmark. >>> >>> Allow migrating mTHP: >>> As mentioned in the previous thread[1], large folios are more susceptible >>> to false sharing issues, leading to pages ping-pong back and forth during >>> numa balancing, which is currently hard to resolve. Therefore, as a start to >>> support mTHP numa balancing, only exclusive mappings are allowed to perform >>> numa migration to avoid the false sharing issues with large folios. Similarly, >>> use the estimated mapcount to skip shared mappings, which seems can work >>> in most cases (?), and we've used folio_estimated_sharers() to skip shared >>> mappings in migrate_misplaced_folio() for numa balancing, seems no real >>> complaints. >> >> IIUC, folio_estimated_sharers() cannot identify multi-thread >> applications. If some mTHP is shared by multiple threads in one > > Right. > Wasn't this "false sharing" previously raised/described by Mel in this context? >> process, how to deal with that? > > IMHO, seems the should_numa_migrate_memory() already did something to help? > > ...... > if (!cpupid_pid_unset(last_cpupid) && > cpupid_to_nid(last_cpupid) != dst_nid) > return false; > > /* Always allow migrate on private faults */ > if (cpupid_match_pid(p, last_cpupid)) > return true; > ...... > > If the node of the CPU that accessed the mTHP last time is different > from this time, which means there is some contention for that mTHP among > threads. So it will not allow migration. > > If the contention for the mTHP among threads is light or the accessing > is relatively stable, then we can allow migration? > >> For example, I think that we should avoid to migrate on the first fault >> for mTHP in should_numa_migrate_memory(). >> >> More thoughts? Can we add a field in struct folio for mTHP to count >> hint page faults from the same node? > > IIUC, we do not need add a new field for folio, seems we can reuse > ->_flags_2a field. But how to use it? If there are multiple consecutive > NUMA faults from the same node, then allow migration? _flags_2a cannot be used. You could place something after _deferred_list IIRC. But only for folios with order>1. But I also wonder how one could achieve that using a new field. -- Cheers, David / dhildenb