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[2003:cb:c73e:8900:2d8:c9f0:f3fb:d4fd]) by smtp.gmail.com with ESMTPSA id l35-20020a05600c1d2300b0040839fcb217sm11233236wms.8.2023.11.14.03.35.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 14 Nov 2023 03:35:40 -0800 (PST) Message-ID: <1b4de866-df27-46fa-81fa-6818a48d8cc1@redhat.com> Date: Tue, 14 Nov 2023 12:35:39 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH] mm: support large folio numa balancing To: John Hubbard , Baolin Wang , Kefeng Wang , akpm@linux-foundation.org Cc: ying.huang@intel.com, willy@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <606d2d7a-d937-4ffe-a6f2-dfe3ae5a0c91@redhat.com> <70973a55-63a0-4a85-abe5-d8681fdb3886@huawei.com> <00372b9e-6020-64b7-1381-e88d9744ed05@nvidia.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: <00372b9e-6020-64b7-1381-e88d9744ed05@nvidia.com> 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: 8bit X-Rspamd-Queue-Id: 3B25C40014 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: isawwo76rayj3iwb3xxpzwcrciyw19b9 X-HE-Tag: 1699961745-420571 X-HE-Meta: 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 jWYttgTC o+ItGY0J96ejsXiWZNewxiZp0WZSb79PU2SERRj0dxI2cDUB8JhPohCkboJ5Ohwf5rB2X+y2OSXiOJAQENDNo2DLAkdSe/ENmWtQygarPC8Sy4Z+1F2xYpYqeGLBgpA7mY5umlHvk1eWjriot2EBpcfL3BhykKjIsRcJYZRHGV5QSvOTyxUuRG2Wj8WY+qHTgTEEn7xnpsqPCsPlFsmlYgu/SGqRjemQsSGHt2q7kBt/BD48nmsHI2TFQy0yfJFcH43hZVx9uVsl0A22XmeROsWtBUeYfTFhJvY4WLQ/P5+m82l2penOBAezeWPNrrv+X7VXNLajM/QNrWU25yv9YlCwrIgjOLSSb3GNzGPLcClkThPjUXPP8fE/RCY1MLtCIrQDiD6YZU9zyfXBDIl7TZ0cwUVJ724TDVPw5ubMTIvfQ/VLdMOoY3on5Pib1VeH9dfyX 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 13.11.23 23:15, John Hubbard wrote: > On 11/13/23 5:01 AM, Baolin Wang wrote: >> >> >> On 11/13/2023 8:10 PM, Kefeng Wang wrote: >>> >>> >>> On 2023/11/13 18:53, David Hildenbrand wrote: >>>> On 13.11.23 11:45, Baolin Wang wrote: >>>>> Currently, the file pages already support large folio, and >>>>> supporting for >>>>> anonymous pages is also under discussion[1]. Moreover, the numa >>>>> balancing >>>>> code are converted to use a folio by previous thread[2], and the >>>>> migrate_pages >>>>> function also already supports the large folio migration. >>>>> >>>>> So now I did not see any reason to continue restricting NUMA >>>>> balancing for >>>>> large folio. >>>> >>>> I recall John wanted to look into that. CCing him. >>>> >>>> I'll note that the "head page mapcount" heuristic to detect sharers will >>>> now strike on the PTE path and make us believe that a large folios is >>>> exclusive, although it isn't. >>>> >>>> As spelled out in the commit you are referencing: >>>> >>>> commit 6695cf68b15c215d33b8add64c33e01e3cbe236c >>>> Author: Kefeng Wang >>>> Date:   Thu Sep 21 15:44:14 2023 +0800 >>>> >>>>      mm: memory: use a folio in do_numa_page() >>>>      Numa balancing only try to migrate non-compound page in >>>> do_numa_page(), >>>>      use a folio in it to save several compound_head calls, note we use >>>>      folio_estimated_sharers(), it is enough to check the folio >>>> sharers since >>>>      only normal page is handled, if large folio numa balancing is >>>> supported, a >>>>      precise folio sharers check would be used, no functional change >>>> intended. >>>> >>>> >>>> I'll send WIP patches for one approach that can improve the situation >>>> soonish. > > To be honest, I'm still catching up on the approximate vs. exact > sharers case. It wasn't clear to me why a precise sharers count > is needed in order to do this. Perhaps the cost of making a wrong > decision is considered just too high? Good question, I didn't really look into the impact for the NUMA hinting case where we might end up not setting TNF_SHARED although it is shared. For other folio_estimate_sharers() users it's more obvious. As a side note, it could have happened already in corner cases (e.g., concurrent page migration of a small folio). If precision as documented in that commit is really required remains to be seen -- just wanted to spell it out. -- Cheers, David / dhildenb