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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 6ABF4E66882 for ; Fri, 19 Dec 2025 20:52:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=i1/SJXZ90FI5UUfT5V9hfmtsaDq+2j5bDl9O0wW8jvQ=; b=BCEzyU4Cj2NlmXgvy76S/SY5jo uOxQrWjaMK+Da3FlmTCmFCrmPesqFUyAyxcC02tV6jwfANmagdVqsefB39ht3eXO8YMEwrH7mG242 naJaXRx+gqtptgi5OQfNLFIIqR35hATqEUvD57EaCMzwc1ThY2ThMUsPXuRYLDPDebrHUvrp8jBf3 BP9/1ctH+QjCIsAQ9PJ/kSmm2sFextMVsG3+IgyHd76oyocPs87a1zORfn90ktqUgZp3RpRdgzW0Z HPs3lxWDi83xiHOio0D7RRuw7Obv/vGXkUaXn9WKp5T4WSjkwnDsADG2Fao+ZS2cqJ+gW6Qptm3kw Y+4WZJjQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vWhSc-0000000AyNe-4BxK; Fri, 19 Dec 2025 20:52:27 +0000 Received: from mgamail.intel.com ([192.198.163.9]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vWhSb-0000000AyMx-0OTN for linux-arm-kernel@lists.infradead.org; Fri, 19 Dec 2025 20:52:26 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1766177545; x=1797713545; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=1UnP1phlC1N1TzoJ+erXdvhZj4LIIeRmGQfpPPyOIYU=; b=J6xlbBY+dHeYJl002ree9tnIIH8rDFsW/XntnI/KQE46usbhuo7T/ORt gs1lGVbTshbCksA95zrdldG2Narb4daNo+D1UHxppi+jn1CdS1u06Duy9 EDZJc0oORTZT1SV4UHuDqOk0Z8t5ASOqz6rGJWusL8ulLz9EAti8iby8w d33Yyb1EOpRTU/7t9dIAXg1ISK31CAZ330iVUR+28CGqYWgUVatm2WieZ 0jn4nSJJjB88PazXrAuRTnAn4x2t6agi29GHsqshg/qa0JqAl7SWDdb3m 5ACVxzPChTpWN8WgLhrIxYJkx5SwsQY2G7ZTfVHFIZVcOSktucQW+iPto Q==; X-CSE-ConnectionGUID: up3xQk3+TtGTsn8b8eO2bw== X-CSE-MsgGUID: oMtVBUIDQZSXGFj1UnGT9A== X-IronPort-AV: E=McAfee;i="6800,10657,11647"; a="78856571" X-IronPort-AV: E=Sophos;i="6.21,162,1763452800"; d="scan'208";a="78856571" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by fmvoesa103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Dec 2025 12:52:24 -0800 X-CSE-ConnectionGUID: 98Uh3zVhTE+23i7eXdgOKA== X-CSE-MsgGUID: bx3AzxBJRcaevFLfuS8vuQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.21,162,1763452800"; d="scan'208";a="199196097" Received: from schen9-mobl4.amr.corp.intel.com (HELO [10.125.111.100]) ([10.125.111.100]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Dec 2025 12:52:22 -0800 Message-ID: Date: Fri, 19 Dec 2025 12:52:21 -0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/4] arch/*: increase lowmem size to avoid highmem use To: Arnd Bergmann , Arnd Bergmann , linux-mm@kvack.org Cc: Andrew Morton , Andreas Larsson , Christophe Leroy , Dave Hansen , Jason Gunthorpe , Linus Walleij , Matthew Wilcox , Richard Weinberger , Russell King , linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Michal Simek , "David Hildenbrand (Red Hat)" , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Nishanth Menon , Lucas Stach References: <20251219161559.556737-1-arnd@kernel.org> <20251219161559.556737-2-arnd@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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251219_125225_152427_80479EFA X-CRM114-Status: GOOD ( 16.14 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 12/19/25 12:20, Arnd Bergmann wrote: >> For simplicity, I think this can just be: >> >> - default VMSPLIT_3G >> + default VMSPLIT_2G >> >> I doubt the 2G vs. 2G_OPT matters in very many cases. If it does, folks >> can just set it in their config manually. >> >> But, in the end, I don't this this matters all that much. If you think >> having x86 be consistent with ARM, for example, is more important and >> ARM really wants this complexity, I can live with it. > Yes, I think we do want the default of VMSPLIT_3G_OPT for > configs that have neither highmem nor lpae, otherwise the most > common embedded configs go from 3072 MiB to 1792 MiB of virtual > addressing, and that is much more likely to cause regressions > than the 2816 MiB default. > > It would be nice to not need the VMSPLIT_2G default for PAE/LPAE, > but that seems like a larger change. The only thing we'd "regress" would be someone who is repeatedly starting from scratch with a defconfig and expecting defconfig to be the same all the time. I honestly think that's highly unlikely. If folks are upgrading and _actually_ exposed to regressions, they've got an existing config and won't be hit by these defaults at *all*. They won't actually regress. In other words, I think we can be a lot more aggressive about defaults than with the feature set we support. I'd much rather add complexity in here for solving a real problem, like if we have armies of 32-bit x86 users constantly starting new projects from scratch and using defconfigs. I'd _really_ like to keep the defaults as simple as possible.