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[2003:d8:2f3e:5900:27aa:5f4a:b65c:3d3c]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a0b300873dsm6766886f8f.78.2025.05.08.03.55.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 08 May 2025 03:55:51 -0700 (PDT) Message-ID: <0979ce4e-d316-477c-872e-d3f9e47690e5@redhat.com> Date: Thu, 8 May 2025 12:55:48 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/3] mm: Add generic helper to hint a large folio To: Dev Jain , akpm@linux-foundation.org Cc: Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, vbabka@suse.cz, jannh@google.com, pfalcato@suse.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org, peterx@redhat.com, ryan.roberts@arm.com, mingo@kernel.org, libang.li@antgroup.com, maobibo@loongson.cn, zhengqi.arch@bytedance.com, baohua@kernel.org, anshuman.khandual@arm.com, willy@infradead.org, ioworker0@gmail.com, yang@os.amperecomputing.com References: <20250506050056.59250-1-dev.jain@arm.com> <20250506050056.59250-3-dev.jain@arm.com> <887fb371-409e-4dad-b4ff-38b85bfddf95@redhat.com> From: David Hildenbrand Content-Language: en-US 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: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit >> (2) Do we really need "must be part of the same folio", or could be just >> batch over present >> ptes that map consecutive PFNs? In that case, a helper that avoids >> folio_pte_batch() completely >> might be better. >> > I am not sure I get you here. folio_pte_batch() seems to be the simplest > thing we can do as being done around in the code elsewhere, I am not > aware of any alternate. If we don't need the folio, then we can have a batching function that doesn't require the folio. Likely, we could even factor that (non-folio batching) out from folio_pte_batch(). The recent fix [1] might make that easier. See below. So my question is: is something relying on all of these PTEs to point at the same folio? [1] https://lkml.kernel.org/r/20250502215019.822-2-arkamar@atlas.cz Something like this: (would need kerneldoc, probably remove "addr" parameter from folio_pte_batch(), and look into other related cleanups as discussed with Andrew) From f56f67ee5ae9879adb99a8da37fa7ec848c4d256 Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Thu, 8 May 2025 12:53:52 +0200 Subject: [PATCH] tmp Signed-off-by: David Hildenbrand --- mm/internal.h | 84 ++++++++++++++++++++++++++++----------------------- 1 file changed, 46 insertions(+), 38 deletions(-) diff --git a/mm/internal.h b/mm/internal.h index 25a29872c634b..53ff8f8a7c8f9 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -217,36 +217,8 @@ static inline pte_t __pte_batch_clear_ignored(pte_t pte, fpb_t flags) return pte_wrprotect(pte_mkold(pte)); } -/** - * folio_pte_batch - detect a PTE batch for a large folio - * @folio: The large folio to detect a PTE batch for. - * @addr: The user virtual address the first page is mapped at. - * @start_ptep: Page table pointer for the first entry. - * @pte: Page table entry for the first page. - * @max_nr: The maximum number of table entries to consider. - * @flags: Flags to modify the PTE batch semantics. - * @any_writable: Optional pointer to indicate whether any entry except the - * first one is writable. - * @any_young: Optional pointer to indicate whether any entry except the - * first one is young. - * @any_dirty: Optional pointer to indicate whether any entry except the - * first one is dirty. - * - * Detect a PTE batch: consecutive (present) PTEs that map consecutive - * pages of the same large folio. - * - * All PTEs inside a PTE batch have the same PTE bits set, excluding the PFN, - * the accessed bit, writable bit, dirty bit (with FPB_IGNORE_DIRTY) and - * soft-dirty bit (with FPB_IGNORE_SOFT_DIRTY). - * - * start_ptep must map any page of the folio. max_nr must be at least one and - * must be limited by the caller so scanning cannot exceed a single page table. - * - * Return: the number of table entries in the batch. - */ -static inline int folio_pte_batch(struct folio *folio, unsigned long addr, - pte_t *start_ptep, pte_t pte, int max_nr, fpb_t flags, - bool *any_writable, bool *any_young, bool *any_dirty) +static inline int pte_batch(pte_t *start_ptep, pte_t pte, int max_nr, + fpb_t flags, bool *any_writable, bool *any_young, bool *any_dirty) { pte_t expected_pte, *ptep; bool writable, young, dirty; @@ -259,14 +231,6 @@ static inline int folio_pte_batch(struct folio *folio, unsigned long addr, if (any_dirty) *any_dirty = false; - VM_WARN_ON_FOLIO(!pte_present(pte), folio); - VM_WARN_ON_FOLIO(!folio_test_large(folio) || max_nr < 1, folio); - VM_WARN_ON_FOLIO(page_folio(pfn_to_page(pte_pfn(pte))) != folio, folio); - - /* Limit max_nr to the actual remaining PFNs in the folio we could batch. */ - max_nr = min_t(unsigned long, max_nr, - folio_pfn(folio) + folio_nr_pages(folio) - pte_pfn(pte)); - nr = pte_batch_hint(start_ptep, pte); expected_pte = __pte_batch_clear_ignored(pte_advance_pfn(pte, nr), flags); ptep = start_ptep + nr; @@ -300,6 +264,50 @@ static inline int folio_pte_batch(struct folio *folio, unsigned long addr, return min(nr, max_nr); } +/** + * folio_pte_batch - detect a PTE batch for a large folio + * @folio: The large folio to detect a PTE batch for. + * @addr: The user virtual address the first page is mapped at. + * @start_ptep: Page table pointer for the first entry. + * @pte: Page table entry for the first page. + * @max_nr: The maximum number of table entries to consider. + * @flags: Flags to modify the PTE batch semantics. + * @any_writable: Optional pointer to indicate whether any entry except the + * first one is writable. + * @any_young: Optional pointer to indicate whether any entry except the + * first one is young. + * @any_dirty: Optional pointer to indicate whether any entry except the + * first one is dirty. + * + * Detect a PTE batch: consecutive (present) PTEs that map consecutive + * pages of the same large folio. + * + * All PTEs inside a PTE batch have the same PTE bits set, excluding the PFN, + * the accessed bit, writable bit, dirty bit (with FPB_IGNORE_DIRTY) and + * soft-dirty bit (with FPB_IGNORE_SOFT_DIRTY). + * + * start_ptep must map any page of the folio. max_nr must be at least one and + * must be limited by the caller so scanning cannot exceed a single page table. + * + * Return: the number of table entries in the batch. + */ +static inline int folio_pte_batch(struct folio *folio, unsigned long addr, + pte_t *start_ptep, pte_t pte, int max_nr, fpb_t flags, + bool *any_writable, bool *any_young, bool *any_dirty) +{ + + VM_WARN_ON_FOLIO(!pte_present(pte), folio); + VM_WARN_ON_FOLIO(!folio_test_large(folio) || max_nr < 1, folio); + VM_WARN_ON_FOLIO(page_folio(pfn_to_page(pte_pfn(pte))) != folio, folio); + + /* Limit max_nr to the actual remaining PFNs in the folio we could batch. */ + max_nr = min_t(unsigned long, max_nr, + folio_pfn(folio) + folio_nr_pages(folio) - pte_pfn(pte)); + + return pte_batch(start_ptep, pte, max_nr, flags, any_writable, any_young, + any_dirty); +} + /** * pte_move_swp_offset - Move the swap entry offset field of a swap pte * forward or backward by delta -- 2.49.0 -- Cheers, David / dhildenb