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 X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6D54CC00319 for ; Thu, 21 Feb 2019 23:51:07 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 254212083E for ; Thu, 21 Feb 2019 23:51:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 254212083E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 7DB388E00C8; Thu, 21 Feb 2019 18:50:59 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 73B6E8E00C9; Thu, 21 Feb 2019 18:50:59 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5D9E88E00C8; Thu, 21 Feb 2019 18:50:59 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from mail-pf1-f198.google.com (mail-pf1-f198.google.com [209.85.210.198]) by kanga.kvack.org (Postfix) with ESMTP id 1AD4B8E00B5 for ; Thu, 21 Feb 2019 18:50:59 -0500 (EST) Received: by mail-pf1-f198.google.com with SMTP id g197so329671pfb.15 for ; Thu, 21 Feb 2019 15:50:59 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-original-authentication-results:x-gm-message-state:subject:to:cc :references:from:openpgp:autocrypt:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=COL8a/bhLctZiKFBcotiJ8aqw2nEZHLXmYVqsv0DDyY=; b=djll7goSUe3a3gz9pLBP2NrlGn9ZHUaqJ1RNL6AzXt9RdnsgLz8jhSzZSSqYEmj5C7 hsbze9y10Dn8KAxvQlg8Eew2PCHt8giMtyjONVMur/y56AKQ8WH09UDa58JzFjPz9pyu VdYkP4PiHz876G+Trd8Pcgz2vENq+qQuSYJKWbN32oO7idFPGXp9S0pN6mmrH0zaya1k h4L9YtL91IJhXPZH2FF31WsBkD3n3wjqK9PX29ucqZi6fz4JyG9hLaVDxkL8dKLEKKOa pV1PGZGeB+IRttwZ+AG0rW6m7lIcUZPlt7L6vdBwVCknz3OQNx+BetdoInrjNij3jTY2 znNw== X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of dave.hansen@intel.com designates 192.55.52.115 as permitted sender) smtp.mailfrom=dave.hansen@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Gm-Message-State: AHQUAuZvCkSv9cE7kD4A1UXX+f4JiSkbmFobbeXM5Ep+/GJm6We0ZUHT 29+l6bQzRqpY47B2NqhDNzoxpPhjyuIPDH8P53wg745g7rlIm7vHvRTXn4IwMPD6ZkI2LKhEdic lse3Tgx6f+k2Jd48kw7AqEzo/f0ATuxywibE3wKIV++al0aOY7MXqS3mB912ugPxOXg== X-Received: by 2002:a63:534c:: with SMTP id t12mr1040221pgl.205.1550793058803; Thu, 21 Feb 2019 15:50:58 -0800 (PST) X-Google-Smtp-Source: AHgI3IbewAM/BbCd+D3ph6BAmALEu+Hjf7U/9v5jfsozTRZNvmfKHIBK4aO5KxODT5FDCbqQrRh6 X-Received: by 2002:a63:534c:: with SMTP id t12mr1040196pgl.205.1550793058105; Thu, 21 Feb 2019 15:50:58 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1550793058; cv=none; d=google.com; s=arc-20160816; b=Scj8q8ihKkgdrKAFJwL210MNGkH9DIVxZdXOzuxjXO+h+bd3hftZ0aiXVJ2OBpjmWO XPPhluEFLW1BQS7025WJbTIHukVlcJyJKyhHQOtgNzw17GAqyg5fAgOn4L5GXcIqSAOE DJnhLuniWt2QdIO5Rp1xpMba9azgCdX6J4/z/J/k6CQ2TL+CtLI8UQMyv4sLWP8PKZBi HwoknTkYG2/9SSWHPNuYHNnFbDqdtNRhzN7Ls9rABMO7jvnoRI6EOudYn/KDBbUiN9MC 95sEilF6oDcclkzxpYh3xw6iGrUiiVQL/WJFrWXP9S8PL0lQqNfMqjCGtM1UG6nFtOuR XL1Q== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:content-language:in-reply-to:mime-version :user-agent:date:message-id:autocrypt:openpgp:from:references:cc:to :subject; bh=COL8a/bhLctZiKFBcotiJ8aqw2nEZHLXmYVqsv0DDyY=; b=EtwUVUyK5GadYHrR6V4wSIaDgxwh5GzEU/VSJ+T8qPDd8y6Twbef9HCR6bW2jqXDPP Lc9/8HJcyTKrwkdspHkBha2V1XmcmX0+00c9TTqRGta7nhAmjm7JalsKZVC6liLbQ0Pt G1ULq7dyMt71W9MCmapuLFy6e8xrZeKRBH+OGdgqWoDSFHcW23neI57NV0jG5I85nv3u mWzU4jbWItqYzrRGQGihiDKy1H0SMiHEFqgyPQunfRnKQ4ej9MeDdYn662ROXOJNLQWy 8JB0ZqRPW6ZGzwXMgMykLE4Pw6pRVf42PvRR+urXlvbAFpQdAo/xbCne4gWvNU4C0/vs NBQw== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of dave.hansen@intel.com designates 192.55.52.115 as permitted sender) smtp.mailfrom=dave.hansen@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: from mga14.intel.com (mga14.intel.com. [192.55.52.115]) by mx.google.com with ESMTPS id b3si221941pld.282.2019.02.21.15.50.57 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 21 Feb 2019 15:50:58 -0800 (PST) Received-SPF: pass (google.com: domain of dave.hansen@intel.com designates 192.55.52.115 as permitted sender) client-ip=192.55.52.115; Authentication-Results: mx.google.com; spf=pass (google.com: domain of dave.hansen@intel.com designates 192.55.52.115 as permitted sender) smtp.mailfrom=dave.hansen@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 21 Feb 2019 15:50:57 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,397,1544515200"; d="scan'208";a="301607231" Received: from sthulasi-mobl1.amr.corp.intel.com (HELO [10.254.86.146]) ([10.254.86.146]) by orsmga005.jf.intel.com with ESMTP; 21 Feb 2019 15:50:57 -0800 Subject: Re: question about page tables in DAX/FS/PMEM case To: Larry Bassel , Jerome Glisse Cc: linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20190220230622.GI19341@ubuette> <20190221204141.GB5201@redhat.com> <20190221225827.GA2764@ubuette> From: Dave Hansen Openpgp: preference=signencrypt Autocrypt: addr=dave.hansen@intel.com; keydata= mQINBE6HMP0BEADIMA3XYkQfF3dwHlj58Yjsc4E5y5G67cfbt8dvaUq2fx1lR0K9h1bOI6fC 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/aCccJK18ZwNjFhqr4MliQARAQABtEVEYXZpZCBDaHJp c3RvcGhlciBIYW5zZW4gKEludGVsIFdvcmsgQWRkcmVzcykgPGRhdmUuaGFuc2VuQGludGVs LmNvbT6JAjgEEwECACIFAlQ+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 5TsyLYdPur3TXm7XDBdmmyQVJjnJKYK9AQxj95KlXLVO38lcuQINBFRjzmoBEACyAxbvUEhd 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+ZkptgGjikQARAQABiQIfBBgBAgAJBQJUY85qAhsMAAoJEGg1lTBwyZKw 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 Message-ID: <6e4a5296-0ad0-ab1e-40a0-c1f69d11300a@intel.com> Date: Thu, 21 Feb 2019 15:51:05 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190221225827.GA2764@ubuette> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit 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: On 2/21/19 2:58 PM, Larry Bassel wrote: > AFAIK there is no hardware benefit from sharing the page table > directory within different page table. So the only benefit is the > amount of memory we save. The hardware benefit from schemes like this is that the CPU caches are better utilized. If two processes share page tables, they don't share TLB entries, but they *do* share the contents of the CPU's caches. That will make TLB misses faster. It probably doesn't matter *that* much in practice because the page walker doing TLB fills does a pretty good job of hiding all the latency, but it might matter in extreme cases.