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Shutemov" , Mel Gorman , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Richard Chang , linux-kernel@vger.kernel.org References: <20250509200111.3372279-1-ziy@nvidia.com> <20250509200111.3372279-2-ziy@nvidia.com> <506798aa-0280-4f63-9c0e-d5f2f5d58c3c@redhat.com> <166E73A3-02CE-4023-AE0E-022C9C618C33@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: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: gTPmjX5W7RTFOySl2m-27amC6Hork54MW7fsM2KU20g_1747828643 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: r68f6bjbnpxhu4wghwkaqtd8jwswpphz X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 7C84F40008 X-HE-Tag: 1747828646-977735 X-HE-Meta: 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 iIp21j0T n6u+NUYz/HtBK1kxcG5ML+zbXGUCYSzfJH/wJuFzYRUAoCrYX++Cqy5sepxWaj6knl7dR3+ypNCDhKWXfG9ZCKytbtA0s2FT88QgBPXHF569FUg3XLUqIs8IFy9c8qWzDWLw9R4ispmxxUb4Z60/6VBK6tmvMruXk3b7heFPXtiUiEsCUQWyulPq+NwREPABf/xI9oIrfDItGmQ2Aj69GkdCNKGiacuXhV2HUaCLU/g5sE/vJWETDtDa+b6uqWLwdiKV1+SjqySsdCIAnyXqSgN2me6r/1xAbIcaUSslw/Jz17eWCdNgr+sg4kWCbeCtYE2aTcLBurEP1pAQaXbm7pgVQ4V7mf+/nYpOJA7VBJd/PASoadoMP7fVvnvqLQ5uqybCBcQUtQWE/L9q/RDEOi0ntmiPEpbSpPWCls9DSFt2th6D1tvp+aw4/3CUiQ44+z39PfUhgfisSEGI= 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 21.05.25 13:16, Zi Yan wrote: > On 19 May 2025, at 12:42, David Hildenbrand wrote: > >>>>> +#ifdef CONFIG_MEMORY_ISOLATION >>>>> + if (flags & PB_migrate_isolate_bit) >>>>> + return MIGRATE_ISOLATE; >>>>> +#endif >>>> >>>> If you call get_pfnblock_flags_mask() with MIGRATETYPE_MASK, how could you ever get PB_migrate_isolate_bit? >>> >>> MIGRATETYPE_MASK is ((BIT(PB_migratetype_bits) - 1) | PB_migrate_isolate_bit), >>> so it gets PB_migrate_isolate_bit. >>> >> >> Oh ... that's confusing. >> >>>> >>>> >>>> I think what we should do is >>>> >>>> 1) Rename get_pfnblock_flags_mask() to get_pfnblock_flags() >>>> >>>> 2) Remove the mask parameter >>>> >>>> 3) Perform the masking in all callers. >>> >>> get_pfnblock_flags_mask() is also used by get_pageblock_skip() to >>> get PB_migrate_skip. I do not think we want to include PB_migrate_skip >>> in the mask to confuse readers. >> >> The masking will be handled in the caller. >> >> So get_pageblock_skip() would essentially do a >> >> return get_pfnblock_flags() & PB_migrate_skip_bit; >> >> etc. >> >>> >>>> >>>> >>>> >>>> Maybe, we should convert set_pfnblock_flags_mask() to >>>> >>>> void set_clear_pfnblock_flags(struct page *page, unsigned long >>>> set_flags, unsigned long clear_flags); >>>> >>>> And better, splitting it up (or providing helpers) >>>> >>>> set_pfnblock_flags(struct page *page, unsigned long flags); >>>> clear_pfnblock_flags(struct page *page, unsigned long flags); >>>> >>>> >>>> This implies some more code cleanups first that make the code easier to extend. >>>> >>> >>> The same due to PB_migrate_skip. >>> >>> Based on your suggestion, we could make {set,get}_pfnblock_flags_mask() >>> internal APIs by prepending "__". They are only used by the new >>> {get, set, clear}_pfnblock_flags() and {get, set, clear}_pageblock_{skip, isolate}(). >>> Then use {get, set, clear}_pfnblock_flags() for all migratetype operations. >>> >>> WDYT? >> >> In general, lgtm. I just hope we can avoid the "_mask" part and just handle it in these functions directly? > > After implementing {get, set, clear}_pfnblock_flags(), I find that > get_pfnblock_flags() is easy like you wrote above, but set and clear are not, > since migratetype and skip/isolate bits are in the same word, meaning > I will need to first read them out, change the field, then write them back. Like existing set_pfnblock_flags_mask() I guess, with the try_cmpxchg() loop. > But it will cause inconsistency if there is a parallel writer to the same > word. So for set and clear, mask is required. > > I can try to implement {get, set, clear}_pfnblock_bits(page,pfn, bits) to > only handle standalone bits by using the given @bits as the mask and > {set,get}_pageblock_migratetype() still use the mask. We'd still have to do the try_cmpxchg() when dealing with multiple bits, right? For single bits, we could just use set_bit() etc. -- Cheers, David / dhildenb