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Fri, 04 Jul 2025 10:10:17 -0700 (PDT) Received: from ziepe.ca ([130.41.10.202]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-702c4d50e20sm15312816d6.72.2025.07.04.10.10.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Jul 2025 10:10:16 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1uXjvT-00000005zBS-3bpa; Fri, 04 Jul 2025 14:10:15 -0300 Date: Fri, 4 Jul 2025 14:10:15 -0300 From: Jason Gunthorpe To: lizhe.67@bytedance.com Cc: alex.williamson@redhat.com, akpm@linux-foundation.org, david@redhat.com, peterx@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2 1/5] mm: introduce num_pages_contiguous() Message-ID: <20250704171015.GJ904431@ziepe.ca> References: <20250704062602.33500-1-lizhe.67@bytedance.com> <20250704062602.33500-2-lizhe.67@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250704062602.33500-2-lizhe.67@bytedance.com> X-Rspamd-Queue-Id: 06A5C160012 X-Stat-Signature: 8i1o8rzdrp6ja4y1aodj9obxcycth1y3 X-Rspam-User: X-Rspamd-Server: rspam05 X-HE-Tag: 1751649017-120143 X-HE-Meta: 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 oCHZsZs3 6q2+slnzAXJnUxoqfy7LJddXJebVjZbFwalebAy9bNDsNkC+tbV8nXoTGltYkwDCneQBJl2CSow7F1nPciSGkL9zhgJfxb48vgtzJV5gK9HG4Q9wHiI/jE7Rnt2lraBezBR33uiEsral8C4kEre5ST41FgcEP2x1PZr9yJvi3eNX/2zdyRC0AewsLoI+e5gtMNxDprEQCkvpHmAyLySxO8of8lxZaDIEaF9WUdYAD95sYf7IUey2nI9+H3Mrs/a05vAZ7W8W79rFnRXHHxFQxtiyHa+RwZHNo7Ppi0jyF5cLDdcdP3jLVKtTjtftdqi1C3zKFbgLNO4InsNDC4KsgK8RYebHP0f6U/bp4v034ULREx9V4GSfXyIEI8g7t04VXMKQtUfb4azf6k1rRBSvHwHzOd+tKCRVhw4uL 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 Fri, Jul 04, 2025 at 02:25:58PM +0800, lizhe.67@bytedance.com wrote: > From: Li Zhe > > Function num_pages_contiguous() determine the number of contiguous > pages starting from the first page in the given array of page pointers. > VFIO will utilize this interface to accelerate the VFIO DMA map process. > > Suggested-by: David Hildenbrand > Signed-off-by: Li Zhe > --- > include/linux/mm.h | 20 ++++++++++++++++++++ > 1 file changed, 20 insertions(+) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 0ef2ba0c667a..1d26203d1ced 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -205,6 +205,26 @@ extern unsigned long sysctl_admin_reserve_kbytes; > #define folio_page_idx(folio, p) ((p) - &(folio)->page) > #endif > > +/* > + * num_pages_contiguous() - determine the number of contiguous pages > + * starting from the first page. > + * > + * @pages: an array of page pointers > + * @nr_pages: length of the array > + */ > +static inline unsigned long num_pages_contiguous(struct page **pages, > + unsigned long nr_pages) Both longs should be size_t I think > +{ > + struct page *first_page = pages[0]; > + unsigned long i; Size_t > + > + for (i = 1; i < nr_pages; i++) > + if (pages[i] != nth_page(first_page, i)) > + break; It seems OK. So the reasoning here is this is faster on CONFIG_SPARSEMEM_VMEMMAP/nonsparse and about the same on sparse mem? (or we don't care?) Jason