From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.20]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2224C1EE7DC; Tue, 11 Feb 2025 20:53:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.20 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739307198; cv=none; b=CJrnQfuCDEkrFWupQ30Bnx/6ZSRVscDKd+CP33nZ8fJ0VIkMdIbLXYqC+/yUnqXi3QOAyAvk2sNiWoJ4drn10K/xqQ02odrTmuqXkPULYUlSe8x4FNBvXxo2wKIPfs5xikNfcvVmLP/nmYW7vzAsnVjuB2+vN66St99axRcpWEM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739307198; c=relaxed/simple; bh=8sphWtJykSdh/06Ktz9t9+80uXqBvCL0k4WcR3tRdhU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=FIuk53F5Jh2ngFBeiiPQ+jHRS3r5xl2GdDymvcn/9x0/Y8aTuQMLw5rRVQif0PtaZpedXZK/2DuVjGZAXG62GgHtM/ZPwzxgWaTtBH/iM1I5BxWITr5kQkroT7tveUQ0ZYaUcOSWVSx/ZbtmndcJZlqPhkMywWofkv6/smerfco= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=jSBZjkuG; arc=none smtp.client-ip=198.175.65.20 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="jSBZjkuG" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1739307197; x=1770843197; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=8sphWtJykSdh/06Ktz9t9+80uXqBvCL0k4WcR3tRdhU=; b=jSBZjkuGtL5JgsLJIQX4LgyF0UMXt5mLi21F8tqkyguSnXLLocgJiDqT 69kxqHl5ziR4Ks1MKhtmaLE9Cx0Gi3H74eljLUM1l9Y2Mw2tcF1DoAj4Z rH7rz/5mDtntIii3Lqo0TRkSPtOY2AKyo+sLkjM5LQKHRGGq7yvBnKJe9 /kqyf48rqV4A2/le/SM3TPmHK1mFUAFY+yuflcJJ+SKr7SHRm7YbB4jYt QAXrccOoHtIaaK0YOxm2rpBmNEMn2BFvVEXtG0hQobijA68fYsOgvtXmb yDDOlo4EVOvUuo18V6TOo85Z1KkozZa9GRPBQ5g9sVKGD+SwuMnxyKDEh w==; X-CSE-ConnectionGUID: mBM01KgKTu2Ty2rrqdLzQg== X-CSE-MsgGUID: i35HvJ3QQp2OKxIq+BApVw== X-IronPort-AV: E=McAfee;i="6700,10204,11342"; a="39640210" X-IronPort-AV: E=Sophos;i="6.13,278,1732608000"; d="scan'208";a="39640210" Received: from orviesa001.jf.intel.com ([10.64.159.141]) by orvoesa112.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Feb 2025 12:53:17 -0800 X-CSE-ConnectionGUID: LXCnERC9RhmWG1D/VhEbPw== X-CSE-MsgGUID: YSCEat7OSRelzneUWD7QDQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.12,224,1728975600"; d="scan'208";a="149807404" Received: from msatwood-mobl.amr.corp.intel.com (HELO [10.125.108.48]) ([10.125.108.48]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Feb 2025 12:53:16 -0800 Message-ID: Date: Tue, 11 Feb 2025 12:53:15 -0800 Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 05/17] x86/cpu/intel: Fix page copy performance for extended Families To: Sohil Mehta , x86@kernel.org, Dave Hansen , Tony Luck Cc: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , Kan Liang , Thomas Gleixner , Borislav Petkov , "H . Peter Anvin" , "Rafael J . Wysocki" , Len Brown , Andy Lutomirski , Viresh Kumar , Fenghua Yu , Jean Delvare , Guenter Roeck , Zhang Rui , Andrew Cooper , David Laight , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-pm@vger.kernel.org, linux-hwmon@vger.kernel.org References: <20250211194407.2577252-1-sohil.mehta@intel.com> <20250211194407.2577252-6-sohil.mehta@intel.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: <20250211194407.2577252-6-sohil.mehta@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/11/25 11:43, Sohil Mehta wrote: > + /* > + * Modern CPUs are generally expected to have a sane fast string > + * implementation. However, the BIOS may disable it on certain CPUs > + * via the architectural FAST_STRING bit. > + */ > + if (IS_ENABLED(CONFIG_X86_64) && (c->x86 == 6 || c->x86 > 15)) > + set_cpu_cap(c, X86_FEATURE_REP_GOOD); I'm not sure the BIOS comment is helpful here. Also, at this point, let's just make the check >=6 (or the >=PPRO equivalent). It will only matter if *all* of these are true: 1. Someone has a 64-bit capable P4 that powers on 2. They're running a 64-bit mainline kernel 3. String copy is *actually* slower than the alternative 4. They are performance sensitive enough to notice We don't even know the answer to #3 for sure. Let's just say what we're doing in a comment: /* Assume that any 64-bit CPU has a good implementation */