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Thu, 19 Feb 2026 17:26:25 -0500 (EST) Date: Thu, 19 Feb 2026 22:26:22 +0000 From: Kiryl Shutsemau To: Matthew Wilcox Cc: lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org, x86@kernel.org, linux-kernel@vger.kernel.org, Andrew Morton , David Hildenbrand , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , Lorenzo Stoakes , "Liam R. Howlett" , Mike Rapoport , Johannes Weiner , Usama Arif Subject: Re: [LSF/MM/BPF TOPIC] 64k (or 16k) base page size on x86 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Queue-Id: 0A8A3C0002 X-Rspamd-Server: rspam02 X-Stat-Signature: 7g1pokxj676dozfererhfdxxbyhnkrus X-HE-Tag: 1771539989-572911 X-HE-Meta: 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 tblmv1rG vvmv3zmWEZdelq7BCvPuYC7XL9CKcffdIG1IuF8XrCO16UcdI5e07tmPCbqHmxbMtCDSscA+drUKxchkKsQbmdbbK1DM1NkmJ49dQbn0HkiRXlYR2B7wxXFy0PLArmVFDpe+hp0JetSl8n4Rur9zdksOlnLZBcljpvTt5BvBGhN3aueuidox6MEik3iSS5c6aGO12I8XpR7DtucgGEvcalxLZt5NAsOCgBU6aE525Nw/60jgB30RgjGcnb/uaLulVr5Rc7TfpsT3El75PQre61Iv/Og== 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 Thu, Feb 19, 2026 at 05:47:22PM +0000, Matthew Wilcox wrote: > On Thu, Feb 19, 2026 at 03:08:51PM +0000, Kiryl Shutsemau wrote: > > On x86, page tables are allocated from the buddy allocator and if PG_SIZE > > is greater than 4 KB, we need a way to pack multiple page tables into a > > single page. We could use the slab allocator for this, but it would > > require relocating the page-table metadata out of struct page. > > Have you looked at the s390/ppc implementations (yes, they're different, > no, that sucks)? No, will check it out tomorrow. > slab seems like the wrong approach to me. I was the first thing that came to mind. I have not put much time into it > There's a third approach that I've never looked at which is to allocate > the larger size, then just use it for N consecutive entries. Yeah, that's a possible way. We would need to populate 16 page table entries of the parent page table. But you don't need to care about fragmentation within the page. -- Kiryl Shutsemau / Kirill A. Shutemov