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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 89A18C25B75 for ; Mon, 3 Jun 2024 13:23:54 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BE5A16B0082; Mon, 3 Jun 2024 09:23:53 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B6DC16B0085; Mon, 3 Jun 2024 09:23:53 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A0E636B0088; Mon, 3 Jun 2024 09:23:53 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 80A106B0082 for ; Mon, 3 Jun 2024 09:23:53 -0400 (EDT) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 35F5D1C1874 for ; Mon, 3 Jun 2024 13:23:53 +0000 (UTC) X-FDA: 82189645146.21.D39982E Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.13]) by imf08.hostedemail.com (Postfix) with ESMTP id 5EEA116001B for ; Mon, 3 Jun 2024 13:23:50 +0000 (UTC) Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=fOOUBaGv; spf=pass (imf08.hostedemail.com: domain of dave.hansen@intel.com designates 198.175.65.13 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=1717421031; 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=FsI4e2iwtiHdNnHZLApYOakz4g06pZw0cZuNFUyop4M=; b=rwIsjoCp24Y5UdJdWIg105Cptx0h7CJUEyRMwnzH65Qlbtvh9U5LRAW5rz6Ob6lu9/JsjP gBVKFCDQ25HbEF8NsSb1l34RD97MsVh9FiIgD9iOMmhGouloN0YmmuwjlkewRTul7ei0qt MDKuFDjemypWk7Cw9p5kyPyW04pJ8dk= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=fOOUBaGv; spf=pass (imf08.hostedemail.com: domain of dave.hansen@intel.com designates 198.175.65.13 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=1717421031; a=rsa-sha256; cv=none; b=5IpDrQvZctmrF1u7BQnD60SdJv9jRkV8v+1TttYtSO6tXwYlm5xBoxsPgxbViV6f/eD6qp EJy0DgVryt/anVckCuHtxZknMZEAataxrP1H5QojY5aoeUeBHG2O+PLOoIJzNnl47W6XkF Fxi65v9Jx0u9q5JbfjSPugQPt4MhUiE= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1717421030; x=1748957030; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=0JmL6NQbUJ4ROho0N3kJCuCT4C0By7SeorqgtqCPtrc=; b=fOOUBaGvU4Tu4v0pUe1/hn/1eVb7cmUThwn6plJaWZRB56eEWIEOmH8l 4cunGV9CrO0fLdlbpo+OACPNAXRIZvgTgHoi2xSg2POJg6fyXiaWUbCzg hAz28aYbGOVj4trt9IQrmTAa8NZhngUrkrdNrEBLIfhrSh8gt6HKLKqSm 8EW0I96QD3CCRMfpv40gjgC9WmXDp91I8JxAAABtrAhATsmj9UHdbv+jV hSQnH1pRCAzwfm9Szeh3r0nRspfQr1v9pV09t9Tnyc8cr1ssx1kbcP+xq N5S9X57JNZiGa1QbqkL81ImLB/zAokbFtdg9j6EEwSJ5vxMZS178V1i43 Q==; X-CSE-ConnectionGUID: 41gvaPpyQuaCzMuiHbFhew== X-CSE-MsgGUID: yCAmJRkNQTeu+I2QncaWlw== X-IronPort-AV: E=McAfee;i="6600,9927,11092"; a="25026026" X-IronPort-AV: E=Sophos;i="6.08,211,1712646000"; d="scan'208";a="25026026" Received: from fmviesa010.fm.intel.com ([10.60.135.150]) by orvoesa105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Jun 2024 06:23:48 -0700 X-CSE-ConnectionGUID: ihKcwV74SuS+DjxijYNvhQ== X-CSE-MsgGUID: p796QR5YQtGjH9FVPFI6tQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.08,211,1712646000"; d="scan'208";a="36956460" Received: from ibganev-desk.amr.corp.intel.com (HELO [10.125.108.143]) ([10.125.108.143]) by fmviesa010-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Jun 2024 06:23:47 -0700 Message-ID: Date: Mon, 3 Jun 2024 06:23:46 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v11 09/12] mm: implement LUF(Lazy Unmap Flush) defering tlb flush when folios get unmapped To: Byungchul Park , David Hildenbrand Cc: Byungchul Park , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel_team@skhynix.com, akpm@linux-foundation.org, ying.huang@intel.com, vernhao@tencent.com, mgorman@techsingularity.net, hughd@google.com, willy@infradead.org, peterz@infradead.org, luto@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, rjgolo@gmail.com References: <20240531092001.30428-1-byungchul@sk.com> <20240531092001.30428-10-byungchul@sk.com> <26dc4594-430b-483c-a26c-7e68bade74b0@redhat.com> <20240603093505.GA12549@system.software.com> 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: <20240603093505.GA12549@system.software.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: 76g661i6819ifq37d9r4soc3ai7r6y31 X-Rspamd-Queue-Id: 5EEA116001B X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1717421030-446594 X-HE-Meta: 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 Px14ceMc t2+6N7PD26AXLP9iXkkZTq6gk1Srkj2OIMP13fohNIOwh1+SpbnvUlPsHbHBPTAMq8QpgozXLdk/Z4O8jaZ89PKveKqhQc4a6QudfJRlhHKVWFGzNl5KnICmLwLRjpFVmr+K9pbzIlYsZGmVnOY8TVRmTOdWeJwzRISZmdFFu2iiPzSwhTo/cGxkDFM+lpJn6/YnQb4JQ81xxeaQu1EiaLiAzUcDPmV1WJekkPY/fu0z8+SU1anVcEXZuWwGTWvHkV1vJ 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 6/3/24 02:35, Byungchul Park wrote: ...> In luf's point of view, the points where the deferred flush should be > performed are simply: > > 1. when changing the vma maps, that might be luf'ed. > 2. when updating data of the pages, that might be luf'ed. It's simple, but the devil is in the details as always. > All we need to do is to indentify the points: > > 1. when changing the vma maps, that might be luf'ed. > > a) mmap and munmap e.i. fault handler or unmap_region(). > b) permission to writable e.i. mprotect or fault handler. > c) what I'm missing. I'd say it even more generally: anything that installs a PTE which is inconsistent with the original PTE. That, of course, includes writes. But it also includes crazy things that we do like uprobes. Take a look at __replace_page(). I think the page_vma_mapped_walk() checks plus the ptl keep LUF at bay there. But it needs some really thorough review. But the bigger concern is that, if there was a problem, I can't think of a systematic way to find it. > 2. when updating data of the pages, that might be luf'ed. > > a) updating files through vfs e.g. file_end_write(). > b) updating files through writable maps e.i. 1-a) or 1-b). > c) what I'm missing. Filesystems or block devices that change content without a "write" from the local system. Network filesystems and block devices come to mind. I honestly don't know what all the rules are around these, but they could certainly be troublesome. There appear to be some interactions for NFS between file locking and page cache flushing. But, stepping back ... I'd honestly be a lot more comfortable if there was even a debugging LUF mode that enforced a rule that said: 1. A LUF'd PTE can't be rewritten until after a luf_flush() occurs 2. A LUF'd page's position in the page cache can't be replaced until after a luf_flush() or *some* other independent set of rules that can tell us when something goes wrong. That uprobes code, for instance, seems like it will work. But I can also imagine writing it ten other ways where it would break when combined with LUF.