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 05752E77198 for ; Mon, 6 Jan 2025 15:55:05 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1E4226B0082; Mon, 6 Jan 2025 10:55:05 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 16D9C6B0083; Mon, 6 Jan 2025 10:55:05 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F02EF6B0088; Mon, 6 Jan 2025 10:55:04 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id CFD4B6B0082 for ; Mon, 6 Jan 2025 10:55:04 -0500 (EST) Received: from smtpin27.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 850A8815BA for ; Mon, 6 Jan 2025 15:55:04 +0000 (UTC) X-FDA: 82977475728.27.A413F24 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.19]) by imf11.hostedemail.com (Postfix) with ESMTP id 6E6E040028 for ; Mon, 6 Jan 2025 15:54:54 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=jBSKFX4n; dmarc=pass (policy=none) header.from=intel.com; spf=pass (imf11.hostedemail.com: domain of dave.hansen@intel.com designates 192.198.163.19 as permitted sender) smtp.mailfrom=dave.hansen@intel.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1736178895; a=rsa-sha256; cv=none; b=0dYjTnWt7qvHXFaaXayNpqlR387GpJ85h/DY6YJUJ1VDIqXzjUavXEZN5aQluCS4Kdfwgk rh2j8DTX0LlLT1JMVINJHdqXAVrorAfdju/KvgQobMgdPYUvYuzpLJao28iTN35ehRtYMa pNN/QnVWDhXCJ+cU5Ke+Lm/FgXOpaGE= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=jBSKFX4n; dmarc=pass (policy=none) header.from=intel.com; spf=pass (imf11.hostedemail.com: domain of dave.hansen@intel.com designates 192.198.163.19 as permitted sender) smtp.mailfrom=dave.hansen@intel.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1736178895; 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=aJqBtLGLikXqjGEJOO/+MEtDy8PFUa0/mBuETwDqgNs=; b=iAOZcL4FV0I9vwB5HsE42qbo5hzxWkUkDoBUW3PDe6BQ5pOd75JLQB8yIe9f3yFgujnoIp n1MBJBjrAexzaABLkK67qRpI3rIMqHiud25IUMSzyImGWv8coCIpXbWDsAoDqrGVosQeR8 JAs9x1rHus94zqzBQKpbMPes+YxVJZA= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1736178894; x=1767714894; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=ml2R2rcU2E0J1NqaZ+aNSBLw5u05xMZHc1LU87c8eGk=; b=jBSKFX4nZtxIPDv3mm0cas+iYU0dTBy0rKNmGyiHjzfvJO2Otsy1H6J2 5jDoPO6dYMexAnHgEaLd24GvwHFe0vbu6zsfSyBmrJoXToPyPD4tk3Tmi 70NcIfrPY8yST5BPH8ikCu1XuUluhVeVaqY6MLT2Nehb3wdayzNiTH+Hp PoMYP4jCsLV6os2UKWuupXmuos+zkSInBFVKJzM00RiNFGuRoRfykpbcL Hh7m1AgvQ1uPbAWYNXaHeUHf2ld9FD7L/EohiwJVDCckN8XJERp+b4rBD /WEKkZqaJzgtb0dKoRyXgzgQfjYIFXAU2qdpSj9IxnOHQhJuvtAi1x+DL g==; X-CSE-ConnectionGUID: rNdj7D9cQFSK8Hx6Ob7zSw== X-CSE-MsgGUID: HHQiPFq/RPeB8GNah22ugA== X-IronPort-AV: E=McAfee;i="6700,10204,11307"; a="35565017" X-IronPort-AV: E=Sophos;i="6.12,293,1728975600"; d="scan'208";a="35565017" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by fmvoesa113.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Jan 2025 07:54:51 -0800 X-CSE-ConnectionGUID: c19zz9oMQEy2zacs0dpSCg== X-CSE-MsgGUID: 3dC5QvYpSIaXMj3S3AL+0g== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.12,293,1728975600"; d="scan'208";a="102673031" Received: from lbogdanm-mobl3.ger.corp.intel.com (HELO [10.124.220.224]) ([10.124.220.224]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Jan 2025 07:54:50 -0800 Message-ID: <5bda5b49-60a0-41d5-8bd9-c52794a645a8@intel.com> Date: Mon, 6 Jan 2025 07:54:50 -0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 01/12] x86/mm: make MMU_GATHER_RCU_TABLE_FREE unconditional To: Peter Zijlstra , Borislav Petkov Cc: Rik van Riel , x86@kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, dave.hansen@linux.intel.com, luto@kernel.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, akpm@linux-foundation.org, nadav.amit@gmail.com, zhengqi.arch@bytedance.com, linux-mm@kvack.org References: <20241230175550.4046587-1-riel@surriel.com> <20241230175550.4046587-2-riel@surriel.com> <20241230184118.GMZ3LpTn3dHvu_bq-p@fat_crate.local> <20250102195609.GB7274@noisy.programming.kicks-ass.net> <20250103121843.GDZ3fVo0r0JRsGImBS@fat_crate.local> <20250104162713.GA22803@noisy.programming.kicks-ass.net> 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: <20250104162713.GA22803@noisy.programming.kicks-ass.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 6E6E040028 X-Stat-Signature: bp193oxkxmxzkhfc7ezq6cw4o6qufhi1 X-HE-Tag: 1736178894-501264 X-HE-Meta: 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 StgnY+zU /9vMCLseIckLq3tMd0Too1ALIXVacKn13hR01yimOG9g6V2rU+43RIJgxsQXyWSKutwEl+Nj2px1grU52wQg6dDwljUui+hhnzafIxcWtQg9JdiAFwa280fVAWs2i4Y8zChY/YekIwEXLy1grlGOn9HCpmB4SVNcGIk+ar200t+nZvRqnGu/60PKF0ZaNyuQL50LvV2c+Ek/Ia0gQai7uydD2ikM1CjGvcUtUeW/u3e9YIMWHkrKVVauUSMGSe+ORbsrXIo8mlS7g2veGo+Lde0ZSotaWekwTH3FZtVR6fT1Q8KlyLcCKIUjffGLLQ4ebTXVz 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 1/4/25 08:27, Peter Zijlstra wrote: >> Or should we make this unconditional on all native because we don't care about >> the overhead and would like to have simpler code. I mean, disabling IRQs vs >> batching and allocating memory...? > The disabling IRQs on the GUP-fast side stays, it acts as a > RCU-read-side section -- also mmu_gather reverts to sending IPIs if it > runs out of memory (extremely rare). > > I don't think there is measurable overhead from doing the separate table > batching, but I'm sure the robots will tell us. We should _try_ to make it unconditional for simplicity if nothing else. BTW, a few years back, some folks at Intel turned on MMU_GATHER_RCU_TABLE_FREE and ran the usual 0day/LKP tests. I _think_ it was when we were exploring the benefits of Intel's IPI-free TLB flushing mechanism. We didn't find anything remarkable either way (IIRC).