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 5089CC021A4 for ; Thu, 13 Feb 2025 20:48:37 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id DB7FB280001; Thu, 13 Feb 2025 15:48:36 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id D40ED6B0088; Thu, 13 Feb 2025 15:48:36 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B93A2280001; Thu, 13 Feb 2025 15:48:36 -0500 (EST) 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 990E76B0085 for ; Thu, 13 Feb 2025 15:48:36 -0500 (EST) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 5E395B22C2 for ; Thu, 13 Feb 2025 20:48:36 +0000 (UTC) X-FDA: 83116109832.01.8FC4E33 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.13]) by imf20.hostedemail.com (Postfix) with ESMTP id 07B721C0005 for ; Thu, 13 Feb 2025 20:48:33 +0000 (UTC) Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=hBC61p4Y; spf=pass (imf20.hostedemail.com: domain of dave.hansen@intel.com designates 192.198.163.13 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=1739479714; 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=6BlmLrvyxwhxkb6ks15ALdDThC5qxSFMbcRqZyRNoh4=; b=iKCXzS3zn8rkP/4uCVEOnFdXqiHj1J+ms2rn3m0XptMEPpGOphHBKgyRdJljN4FHv9vBtt 5lINccvDe2GS9QxaC8GvlXQINhtDelpyfldYR129nP3303EpJrfEERDWujtNXeQMNCq0rx 0Qe+fKzxIKUUiAzhguHm1Z5YZtFergM= ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=hBC61p4Y; spf=pass (imf20.hostedemail.com: domain of dave.hansen@intel.com designates 192.198.163.13 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=1739479714; a=rsa-sha256; cv=none; b=Z9LSWRtAM3hb/jRtlphQR48iz6ZhLaSZOMfZ4Y4bk9pa1oBn8g91+dqfTutEkacEh7X589 B3jnvRshAiABMm0ZXUzL8N9HJ9MUMTQbqqx4ShXeR1E2Sy5qY4tubYtKLAAHuIgx5/X4b0 zsTaeZwLewHiyNqRL7PTebgAjtpCFeg= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1739479714; x=1771015714; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=t6K3PCXljJZY/d7PpkUPcbHoIesQAQORXAmrHcizRJo=; b=hBC61p4Yr8Hfj4YIGeQnL8/UXt+Z75PkwxSHsfRWFZ5I2u1WQYAAG2he qHjjGDHoFQs1F7bUKSrI9ApETpSFMuQoHC8FhqeEgFruCvG8SRLfiOWkY H8wM8rHxxu9IfR2k2lv/BKsjVj3jlQDxrTsLWQLOk0kPivlNjNwqFB9DF YvRNdkJ3/MWzJokevA9WuMZexlxIHIJVq8ovruDbc7wLHRLyKzV6ta3pQ GTay9AmuyN1s5z+Iq0Pe7aKp1smUzwrznnOpYK/81vEYKQ4O9j0Dt4Scj NbeLuObJTBU4ENlBpMt2iYbjCbYCapjwc38Wx+jZhEXpRfLoJ6p0B4Q+R w==; X-CSE-ConnectionGUID: bcdER+WwSjCC0J70G1v9zg== X-CSE-MsgGUID: ZtwK6wsaTEuhWS49L8b8Bg== X-IronPort-AV: E=McAfee;i="6700,10204,11344"; a="43042403" X-IronPort-AV: E=Sophos;i="6.13,282,1732608000"; d="scan'208";a="43042403" Received: from fmviesa003.fm.intel.com ([10.60.135.143]) by fmvoesa107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Feb 2025 12:48:33 -0800 X-CSE-ConnectionGUID: DG9NCrngTtGhi1HlZKjjvQ== X-CSE-MsgGUID: 7O41g2DPQPuJCNWyTGiaTA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.12,224,1728975600"; d="scan'208";a="117384013" Received: from iherna2-mobl4.amr.corp.intel.com (HELO [10.125.108.188]) ([10.125.108.188]) by fmviesa003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Feb 2025 12:48:32 -0800 Message-ID: <62965669-bf1d-461f-9401-20e303c6d619@intel.com> Date: Thu, 13 Feb 2025 12:48:31 -0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RESEND 2/2] x86/locking: Use asm_inline for {,try_}cmpxchg{64,128} emulations To: Uros Bizjak , x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Dennis Zhou , Tejun Heo , Christoph Lameter , "Peter Zijlstra (Intel)" References: <20250213191457.12377-1-ubizjak@gmail.com> <20250213191457.12377-2-ubizjak@gmail.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: <20250213191457.12377-2-ubizjak@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 07B721C0005 X-Stat-Signature: cufrrwyf68igtbr4gak6a5xsckc1cxmo X-HE-Tag: 1739479713-221330 X-HE-Meta: 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 UMnlV8ct D4DR/yRWV9thWR8ln0F0XJoX9If7NcJbxCTq2NcQxAwT47f9i/MmHDNhx+92SL4j8j252XsiAWIHenBm4tj4AohYHulTxAATVH7t76WGqSa1DJB7PQg8xEC2wznI2g149IIeOjNZuRri74fN3N2ssJCi/vteC+9+Z7i06+setOoxdowEDKRLv1oaPNpLOx8fwXcyUglArq9FvxNlNpySlf0kjSSQi3exJXl3+WjPk6n0mg+jtbX2SJMCFxZ9fBkP5c6yf 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 2/13/25 11:14, Uros Bizjak wrote: > According to [1], the usage of asm pseudo directives in the asm template > can confuse the compiler to wrongly estimate the size of the generated > code. ALTERNATIVE macro expands to several asm pseudo directives, so > its usage in {,try_}cmpxchg{64,128} causes instruction length estimate > to fail by an order of magnitude (the compiler estimates the length of > an asm to be more than 20 instructions). Just curious, but how did you come up with the "20 instructions" number? > This wrong estimate further causes unoptimal inlining decisions for > functions that use these locking primitives. > > Use asm_inline instead of just asm. For inlining purposes, the size of > the asm is then taken as the minimum size, ignoring how many instructions > compiler thinks it is. So, the compiler is trying to decide whether to inline a function or not. The bigger it is, the less likely, it is to be inlined. Since it is over-estimating the size of {,try_}cmpxchg{64,128}, it will avoid inlining it when it _should_ be inlining it. Is that it? Is any of this measurable? Is there any objective data to support that this change is a good one? It's quite possible that someone did the "asm" on purpose because over-estimating the size was a good thing.