From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3F2F2EA4FCF for ; Mon, 23 Feb 2026 15:14:46 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9EC626B0005; Mon, 23 Feb 2026 10:14:45 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 9A3536B0089; Mon, 23 Feb 2026 10:14:45 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8A5E36B008A; Mon, 23 Feb 2026 10:14:45 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 77B3C6B0005 for ; Mon, 23 Feb 2026 10:14:45 -0500 (EST) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 131BA1BF99 for ; Mon, 23 Feb 2026 15:14:45 +0000 (UTC) X-FDA: 84476068530.16.7366A91 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.16]) by imf25.hostedemail.com (Postfix) with ESMTP id AB488A0018 for ; Mon, 23 Feb 2026 15:14:40 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=cAi9MoJr; spf=pass (imf25.hostedemail.com: domain of dave.hansen@intel.com designates 198.175.65.16 as permitted sender) smtp.mailfrom=dave.hansen@intel.com; dmarc=pass (policy=none) header.from=intel.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1771859682; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=aNGpgP5w5m3pkn8x0/Cj77PQ5NYjiWM0uMgsqT82pOA=; b=Wdtickza3rTd2FvfMsWxPt4iGfx77HUR/HX7UfsMeVUEzAvxumuxu0JLHlmc5/I8J4h5pJ YCmotV4wbxX+q7QcD3DYD7Rh/JqcnGPdQ0TtEhKq+zTBM4S7hlzspJcINQvrnmJ5kDAvia 0TyGGiWMjsdxjAVZ+v3DOKytAtCk4u8= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=cAi9MoJr; spf=pass (imf25.hostedemail.com: domain of dave.hansen@intel.com designates 198.175.65.16 as permitted sender) smtp.mailfrom=dave.hansen@intel.com; dmarc=pass (policy=none) header.from=intel.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1771859682; a=rsa-sha256; cv=none; b=uFYFsl1ZTJszIy21iEse1TbVRjo1k1jn4v6IXuP7XxpjNgV/eMHrIURLPtQiNfNCmAuf8h TNwJJF/1wW8S/uRTDN8qUC1iEPKSgBNPchIqGYt7e+33w9zr2VjLJF+etB+VunM6xceAL9 11FYHZRj2N29j6TU0wNfEjmec7cUzsw= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1771859681; x=1803395681; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=foG7iHqEXE3wb1GNTWnX+N/uPXbexmQZX4/CBrLJtJM=; b=cAi9MoJrNYvYUVoS2LbfSKpDgbMFHNylFT/SbBAuu4UTZlVqBJz313yb MIbr15OQbywS0uGcWk76pqBOQv1wBW4W6hqGAi5bhyeM9ILYt0vJNBtsw Pj5Ht+2uZmitTo+zTgjsilY7RRqdFCrlikJT4p2XAid1Oc8uSCf0WAknW dDaAaAxQxv9nfsUzyJThP+A1apFbELvflR0kL1+2bpbDeGhqpED5YSK5D rG9XbqylxkGpCswoUakjpvXVrOhSoytggtmyPR/KZClAPuxinEGJw0tSv uc6X4AQwzHcFO/HjtCw2mIegHKtu1S7aWOz/Ys10UYwoC7QaK4GpgCBbA Q==; X-CSE-ConnectionGUID: 2xBVhnLCQPetJ/ekSZ8atA== X-CSE-MsgGUID: 1tD6/0msR567h0s9TQWFaQ== X-IronPort-AV: E=McAfee;i="6800,10657,11710"; a="73033696" X-IronPort-AV: E=Sophos;i="6.21,306,1763452800"; d="scan'208";a="73033696" Received: from orviesa008.jf.intel.com ([10.64.159.148]) by orvoesa108.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Feb 2026 07:14:38 -0800 X-CSE-ConnectionGUID: MhcAawFkStKVj0i8RE9eUA== X-CSE-MsgGUID: s9Gimh/uTLOeVQcaO6VHaA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.21,306,1763452800"; d="scan'208";a="215611874" Received: from dnelso2-mobl.amr.corp.intel.com (HELO [10.125.110.205]) ([10.125.110.205]) by orviesa008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Feb 2026 07:14:38 -0800 Message-ID: <7b414e68-4d0b-4d2b-a664-bbbdf314c0d3@intel.com> Date: Mon, 23 Feb 2026 07:14:39 -0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [LSF/MM/BPF TOPIC] 64k (or 16k) base page size on x86 To: "David Hildenbrand (Arm)" , Kiryl Shutsemau Cc: 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 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> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; keydata= xsFNBE6HMP0BEADIMA3XYkQfF3dwHlj58Yjsc4E5y5G67cfbt8dvaUq2fx1lR0K9h1bOI6fC oAiUXvGAOxPDsB/P6UEOISPpLl5IuYsSwAeZGkdQ5g6m1xq7AlDJQZddhr/1DC/nMVa/2BoY 2UnKuZuSBu7lgOE193+7Uks3416N2hTkyKUSNkduyoZ9F5twiBhxPJwPtn/wnch6n5RsoXsb ygOEDxLEsSk/7eyFycjE+btUtAWZtx+HseyaGfqkZK0Z9bT1lsaHecmB203xShwCPT49Blxz VOab8668QpaEOdLGhtvrVYVK7x4skyT3nGWcgDCl5/Vp3TWA4K+IofwvXzX2ON/Mj7aQwf5W iC+3nWC7q0uxKwwsddJ0Nu+dpA/UORQWa1NiAftEoSpk5+nUUi0WE+5DRm0H+TXKBWMGNCFn c6+EKg5zQaa8KqymHcOrSXNPmzJuXvDQ8uj2J8XuzCZfK4uy1+YdIr0yyEMI7mdh4KX50LO1 pmowEqDh7dLShTOif/7UtQYrzYq9cPnjU2ZW4qd5Qz2joSGTG9eCXLz5PRe5SqHxv6ljk8mb ApNuY7bOXO/A7T2j5RwXIlcmssqIjBcxsRRoIbpCwWWGjkYjzYCjgsNFL6rt4OL11OUF37wL QcTl7fbCGv53KfKPdYD5hcbguLKi/aCccJK18ZwNjFhqr4MliQARAQABzUVEYXZpZCBDaHJp c3RvcGhlciBIYW5zZW4gKEludGVsIFdvcmsgQWRkcmVzcykgPGRhdmUuaGFuc2VuQGludGVs LmNvbT7CwXgEEwECACIFAlQ+9J0CGwMGCwkIBwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEGg1 lTBwyZKwLZUP/0dnbhDc229u2u6WtK1s1cSd9WsflGXGagkR6liJ4um3XCfYWDHvIdkHYC1t MNcVHFBwmQkawxsYvgO8kXT3SaFZe4ISfB4K4CL2qp4JO+nJdlFUbZI7cz/Td9z8nHjMcWYF IQuTsWOLs/LBMTs+ANumibtw6UkiGVD3dfHJAOPNApjVr+M0P/lVmTeP8w0uVcd2syiaU5jB aht9CYATn+ytFGWZnBEEQFnqcibIaOrmoBLu2b3fKJEd8Jp7NHDSIdrvrMjYynmc6sZKUqH2 I1qOevaa8jUg7wlLJAWGfIqnu85kkqrVOkbNbk4TPub7VOqA6qG5GCNEIv6ZY7HLYd/vAkVY E8Plzq/NwLAuOWxvGrOl7OPuwVeR4hBDfcrNb990MFPpjGgACzAZyjdmYoMu8j3/MAEW4P0z F5+EYJAOZ+z212y1pchNNauehORXgjrNKsZwxwKpPY9qb84E3O9KYpwfATsqOoQ6tTgr+1BR CCwP712H+E9U5HJ0iibN/CDZFVPL1bRerHziuwuQuvE0qWg0+0SChFe9oq0KAwEkVs6ZDMB2 P16MieEEQ6StQRlvy2YBv80L1TMl3T90Bo1UUn6ARXEpcbFE0/aORH/jEXcRteb+vuik5UGY 5TsyLYdPur3TXm7XDBdmmyQVJjnJKYK9AQxj95KlXLVO38lczsFNBFRjzmoBEACyAxbvUEhd GDGNg0JhDdezyTdN8C9BFsdxyTLnSH31NRiyp1QtuxvcqGZjb2trDVuCbIzRrgMZLVgo3upr MIOx1CXEgmn23Zhh0EpdVHM8IKx9Z7V0r+rrpRWFE8/wQZngKYVi49PGoZj50ZEifEJ5qn/H Nsp2+Y+bTUjDdgWMATg9DiFMyv8fvoqgNsNyrrZTnSgoLzdxr89FGHZCoSoAK8gfgFHuO54B lI8QOfPDG9WDPJ66HCodjTlBEr/Cwq6GruxS5i2Y33YVqxvFvDa1tUtl+iJ2SWKS9kCai2DR 3BwVONJEYSDQaven/EHMlY1q8Vln3lGPsS11vSUK3QcNJjmrgYxH5KsVsf6PNRj9mp8Z1kIG qjRx08+nnyStWC0gZH6NrYyS9rpqH3j+hA2WcI7De51L4Rv9pFwzp161mvtc6eC/GxaiUGuH BNAVP0PY0fqvIC68p3rLIAW3f97uv4ce2RSQ7LbsPsimOeCo/5vgS6YQsj83E+AipPr09Caj 0hloj+hFoqiticNpmsxdWKoOsV0PftcQvBCCYuhKbZV9s5hjt9qn8CE86A5g5KqDf83Fxqm/ vXKgHNFHE5zgXGZnrmaf6resQzbvJHO0Fb0CcIohzrpPaL3YepcLDoCCgElGMGQjdCcSQ+Ci FCRl0Bvyj1YZUql+ZkptgGjikQARAQABwsFfBBgBAgAJBQJUY85qAhsMAAoJEGg1lTBwyZKw l4IQAIKHs/9po4spZDFyfDjunimEhVHqlUt7ggR1Hsl/tkvTSze8pI1P6dGp2XW6AnH1iayn yRcoyT0ZJ+Zmm4xAH1zqKjWplzqdb/dO28qk0bPso8+1oPO8oDhLm1+tY+cOvufXkBTm+whm +AyNTjaCRt6aSMnA/QHVGSJ8grrTJCoACVNhnXg/R0g90g8iV8Q+IBZyDkG0tBThaDdw1B2l asInUTeb9EiVfL/Zjdg5VWiF9LL7iS+9hTeVdR09vThQ/DhVbCNxVk+DtyBHsjOKifrVsYep WpRGBIAu3bK8eXtyvrw1igWTNs2wazJ71+0z2jMzbclKAyRHKU9JdN6Hkkgr2nPb561yjcB8 sIq1pFXKyO+nKy6SZYxOvHxCcjk2fkw6UmPU6/j/nQlj2lfOAgNVKuDLothIxzi8pndB8Jju KktE5HJqUUMXePkAYIxEQ0mMc8Po7tuXdejgPMwgP7x65xtfEqI0RuzbUioFltsp1jUaRwQZ MTsCeQDdjpgHsj+P2ZDeEKCbma4m6Ez/YWs4+zDm1X8uZDkZcfQlD9NldbKDJEXLIjYWo1PH hYepSffIWPyvBMBTW2W5FRjJ4vLRrJSUoEfJuPQ3vW9Y73foyo/qFoURHO48AinGPZ7PC7TF vUaNOTjKedrqHkaOcqB185ahG2had0xnFsDPlx5y In-Reply-To: <06684dc4-3902-4452-824a-ee2064314d24@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: px9wzsauks8krqok8qri69rqaa7rizas X-Rspamd-Server: rspam11 X-Rspam-User: X-Rspamd-Queue-Id: AB488A0018 X-HE-Tag: 1771859680-823040 X-HE-Meta: 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 YORQWxOZ fm3Oen3fL3MEDGIopv8c7yWq1EpCAhu4M1+Ee33UaGTNHeRpsEcfPL5VrtMt5GtWV1sXgzqpXWSpLdI3tAwTTAyS88w9GEi7uZhdqjJwwlCKJtP0cMH8mAES+Z2ErezY56wJluCuyqfvau8Nq8XjHArBrxg9E4h6ojZ4Fwj+wjOHKKM7yx4/WCNixYytilo5W4XW5aFLrn/wcpizx1lH4fph265JuWnMWs9v3 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 2/23/26 03:27, David Hildenbrand (Arm) wrote: ... >> BTW, x86-64 SysV ABI allows for 64k page size: >> >>     Systems are permitted to use any power-of-two page size between >>     4KB and 64KB, inclusive. >> >> But it doesn't work in practice. > > Even in well controlled environments you would run in a hyperscaler? I think what Kirill is trying to say is that "it breaks userspace". ;) A hyperscaler (or other "embedded" environment) might be willing or able to go fix up userspace breakage. I would suspect our high frequency trading friends would be all over this if it shaved a microsecond off their receive times. The more important question is what it breaks and how badly it breaks things. 5-level paging, for instance, broke some JITs that historically used the new (>48) upper virtual address bits for metadata. The gains from 5-level paging were big enough and the userspace breakage was confined and fixable enough that 5-level paging was viable. I'm not sure which side a larger base page side will fall on, though. Is it going to be an out-of-tree hack that a few folks use, or will it be more like 5-level paging and be good enough that it goes into mainline?