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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-483a316eb08sm301960225e9.0.2026.02.23.08.34.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Feb 2026 08:34:25 -0800 (PST) Date: Mon, 23 Feb 2026 16:34:23 +0000 From: David Laight To: Dave Hansen Cc: "David Hildenbrand (Arm)" , Kiryl Shutsemau , Kalesh Singh , lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org, x86@kernel.org, linux-kernel@vger.kernel.org, Andrew Morton , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , Lorenzo Stoakes , "Liam R. Howlett" , Mike Rapoport , Matthew Wilcox , Johannes Weiner , Usama Arif Subject: Re: [LSF/MM/BPF TOPIC] 64k (or 16k) base page size on x86 Message-ID: <20260223163423.61a19e5c@pumpkin> In-Reply-To: <7b414e68-4d0b-4d2b-a664-bbbdf314c0d3@intel.com> References: <915aafb3-d1ff-4ae9-8751-f78e333a1f5f@kernel.org> <17c5708d-3859-49a5-814e-bc3564bc3ac6@kernel.org> <32ed82dd-62c3-4a5c-8bae-9465afd7e75f@kernel.org> <06684dc4-3902-4452-824a-ee2064314d24@kernel.org> <7b414e68-4d0b-4d2b-a664-bbbdf314c0d3@intel.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 7FE2440002 X-Stat-Signature: oee3hm7adnsizzrjkpmzfs8m6rbzkwij X-HE-Tag: 1771864467-139650 X-HE-Meta: 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 KL5f+4Tl vt2He/xX4Rnc7wP9szXXQdZre3o4HtKdlKINB1EKbDsn0WxT1ytfTSWxcC0XO8ctk5U9NKsZ/m8p5CCHw52YW4BU+QIXx4SboZNOrN+AZS/CKwGBISuakH2vHq9G8acueTD1lFv2a2BS5FujiWm4z/3WhpaYeBKA5Tp+KGUGd02H8nWGbhmU75vKxwY+FVcJdbmfln81KMFOUWAlVSc7dXQa2gBcqVFOp9FIFr2FU3D7j4qP7cCvni/cJ+i3KESPTWKl5g83SpAn3zLmYc/gKDVCaXUeuU+pvKCHmLAivPqWg/sIYqHxeU+VQMvMTD/f9DhSpIDkj9UlRgj+0bL1PVhC2NA89glFuaen4PEsFxx6Xr6s9WMVxvJkdTgDzVXczmPZEFv9dF8NXVgVWFF1HT0xHdZxE8S78v67vAcv/ec12YNM6w9d8NPDBVr7r+ypE+tMXihvGjghSq6Q= 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 Mon, 23 Feb 2026 07:14:39 -0800 Dave Hansen wrote: > On 2/23/26 03:27, David Hildenbrand (Arm) wrote: > ... > >> BTW, x86-64 SysV ABI allows for 64k page size: > >> > >> =C2=A0=C2=A0=C2=A0=C2=A0Systems are permitted to use any power-of-two = page size between > >> =C2=A0=C2=A0=C2=A0=C2=A04KB and 64KB, inclusive. > >> > >> But it doesn't work in practice. =20 > >=20 > > Even in well controlled environments you would run in a hyperscaler? =20 >=20 > I think what Kirill is trying to say is that "it breaks userspace". ;) With a 4k physical page what stops you dynamically splitting the 64k a 'struct page' references into 16 4k pages (using an extra dynamically allocated structure)? I'm not thinking it would happen that often, but it would solve the problem of 4k aligned .data and (probably) mmap() of small files. If the cpu supports TLB coalescing there could easily be a net gain using 64k pages for most of a program binary. David