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[2003:cb:c725:e600:4063:2059:fd18:9d65]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4247d0b6355sm51444295e9.2.2024.06.21.00.31.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 21 Jun 2024 00:31:18 -0700 (PDT) Message-ID: <10cd22d3-cb58-4ec9-a22d-5b8555044623@redhat.com> Date: Fri, 21 Jun 2024 09:31:17 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 2/2] mm/migrate: move NUMA hinting fault folio isolation + checks under PTL To: Baolin Wang , linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Andrew Morton References: <20240620212935.656243-1-david@redhat.com> <20240620212935.656243-3-david@redhat.com> <05b89531-4103-49cb-bbbf-5a2cfaa3106b@linux.alibaba.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: <05b89531-4103-49cb-bbbf-5a2cfaa3106b@linux.alibaba.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: 7bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: C811540014 X-Stat-Signature: 9d7xkxq8oqyzuyqb3xxybntqwjhog7y6 X-Rspam-User: X-HE-Tag: 1718955083-781373 X-HE-Meta: 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 cUWp9C0J UVNPuxAcWLwjVTX1E1oEJw91mJx++XUtm5Ls4tOFib9SnqQ96uYJkjDjQgmgvRWeSizmOw7qcTlmnTxgkX+6xOlv838hKnW7wJmPWZNUOf4Cr7fE6Jti7v8fwNp2UpF5XgoioHwXUr3Irxf8ZfBcqotAHSqlp76bx/b4tPvh5JLeIKmd7ucp2KvcGtpmKnRbQtZZGH7s/iX2s57Wz8loPuH+pXzCz0Z1RH8Bvng5C8wPovM4wl/Sbc9ns/YhqpIcvlwNiy0oY0baVbp4eimQU7UFjalQz1z89PbSTMfrV5X1VVs82D+jkQmHfN9zbNa7fLadjEwlXQkh8c35iWY+1ign9DBNHnJq0Vs7E8T7NJMTBpTMgJd5v07a03YEbZFcayJ7R9p24X6mg3QA= 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 21.06.24 06:07, Baolin Wang wrote: > > > On 2024/6/21 05:29, David Hildenbrand wrote: >> Currently we always take a folio reference even if migration will not >> even be tried or isolation failed, requiring us to grab+drop an additional >> reference. >> >> Further, we end up calling folio_likely_mapped_shared() while the folio >> might have already been unmapped, because after we dropped the PTL, that >> can easily happen. We want to stop touching mapcounts and friends from >> such context, and only call folio_likely_mapped_shared() while the folio >> is still mapped: mapcount information is pretty much stale and unreliable >> otherwise. >> >> So let's move checks into numamigrate_isolate_folio(), rename that >> function to migrate_misplaced_folio_prepare(), and call that function >> from callsites where we call migrate_misplaced_folio(), but still with >> the PTL held. >> >> We can now stop taking temporary folio references, and really only take >> a reference if folio isolation succeeded. Doing the >> folio_likely_mapped_shared() + golio isolation under PT lock is now similar >> to how we handle MADV_PAGEOUT. > > s/golio/folio > > Make sense to me. Feel free to add: > Reviewed-by: Baolin Wang Thanks! [...] >> node_stat_mod_folio(folio, NR_ISOLATED_ANON + folio_is_file_lru(folio), >> nr_pages); >> - >> - /* >> - * Isolating the folio has taken another reference, so the >> - * caller's reference can be safely dropped without the folio >> - * disappearing underneath us during migration. >> - */ >> - folio_put(folio); >> - return 1; >> + return 0; >> } > > (just a nit: returning boolean seems more readable) "return true" on success really is nasty in a code base where most functions return "0" on success. Like most functions in mm/migrate.c -- like migrate_pages() -- do. Thanks! -- Cheers, David / dhildenb