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[2003:cb:c74e:ff00:f734:227:6936:cdab]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4409d2ac5a9sm34371385e9.23.2025.04.24.14.11.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 24 Apr 2025 14:11:45 -0700 (PDT) Message-ID: <0eae5cc8-5714-44dc-97b4-e1b991c0e918@redhat.com> Date: Thu, 24 Apr 2025 23:11:43 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 1/7] mm: Introduce for_each_valid_pfn() and use it from reserve_bootmem_region() To: David Woodhouse , Mike Rapoport Cc: Andrew Morton , "Sauerwein, David" , Anshuman Khandual , Ard Biesheuvel , Catalin Marinas , Marc Zyngier , Mark Rutland , Mike Rapoport , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Ruihan Li References: <20250423133821.789413-1-dwmw2@infradead.org> <20250423133821.789413-2-dwmw2@infradead.org> 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: <20250423133821.789413-2-dwmw2@infradead.org> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: ajmFa7PrzYgosHdct9K9jafibixu2NpH0uy_BY8M3yM_1745529106 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: qy6ng4px7dsbbm4wh8bf3smwf87zduoh X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 71C4F100009 X-Rspam-User: X-HE-Tag: 1745529109-613187 X-HE-Meta: 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 ui5IdOY/ 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 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 23.04.25 15:33, David Woodhouse wrote: > From: David Woodhouse > > Especially since commit 9092d4f7a1f8 ("memblock: update initialization > of reserved pages"), the reserve_bootmem_region() function can spend a > significant amount of time iterating over every 4KiB PFN in a range, > calling pfn_valid() on each one, and ultimately doing absolutely nothing. > > On a platform used for virtualization, with large NOMAP regions that > eventually get used for guest RAM, this leads to a significant increase > in steal time experienced during kexec for a live update. > > Introduce for_each_valid_pfn() and use it from reserve_bootmem_region(). > This implementation is precisely the same naïve loop that the function > used to have, but subsequent commits will provide optimised versions > for FLATMEM and SPARSEMEM, and this version will remain for those > architectures which provide their own pfn_valid() implementation, > until/unless they also provide a matching for_each_valid_pfn(). > > Signed-off-by: David Woodhouse > Reviewed-by: Mike Rapoport (Microsoft) > --- > include/linux/mmzone.h | 10 ++++++++++ > mm/mm_init.c | 23 ++++++++++------------- > 2 files changed, 20 insertions(+), 13 deletions(-) > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 6ccec1bf2896..230a29c2ed1a 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -2177,6 +2177,16 @@ void sparse_init(void); > #define subsection_map_init(_pfn, _nr_pages) do {} while (0) > #endif /* CONFIG_SPARSEMEM */ > > +/* > + * Fallback case for when the architecture provides its own pfn_valid() but > + * not a corresponding for_each_valid_pfn(). > + */ > +#ifndef for_each_valid_pfn > +#define for_each_valid_pfn(_pfn, _start_pfn, _end_pfn) \ > + for ((_pfn) = (_start_pfn); (_pfn) < (_end_pfn); (_pfn)++) \ > + if (pfn_valid(_pfn)) > +#endif > + > #endif /* !__GENERATING_BOUNDS.H */ > #endif /* !__ASSEMBLY__ */ > #endif /* _LINUX_MMZONE_H */ > diff --git a/mm/mm_init.c b/mm/mm_init.c > index 9659689b8ace..41884f2155c4 100644 > --- a/mm/mm_init.c > +++ b/mm/mm_init.c > @@ -777,22 +777,19 @@ static inline void init_deferred_page(unsigned long pfn, int nid) > void __meminit reserve_bootmem_region(phys_addr_t start, > phys_addr_t end, int nid) > { > - unsigned long start_pfn = PFN_DOWN(start); > - unsigned long end_pfn = PFN_UP(end); > + unsigned long pfn; > > - for (; start_pfn < end_pfn; start_pfn++) { > - if (pfn_valid(start_pfn)) { > - struct page *page = pfn_to_page(start_pfn); > + for_each_valid_pfn (pfn, PFN_DOWN(start), PFN_UP(end)) { ^ space should be removed Acked-by: David Hildenbrand -- Cheers, David / dhildenb