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 980C2C54E49 for ; Thu, 7 Mar 2024 11:20:27 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2ADA26B0160; Thu, 7 Mar 2024 06:20:27 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 25DB86B0161; Thu, 7 Mar 2024 06:20:27 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0D7846B0162; Thu, 7 Mar 2024 06:20:27 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id F23FA6B0160 for ; Thu, 7 Mar 2024 06:20:26 -0500 (EST) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id C81C11206C0 for ; Thu, 7 Mar 2024 11:20:26 +0000 (UTC) X-FDA: 81869999652.02.189DB5E Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf24.hostedemail.com (Postfix) with ESMTP id 91365180008 for ; Thu, 7 Mar 2024 11:20:24 +0000 (UTC) Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=dB1VamwR; spf=pass (imf24.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1709810424; 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=T3S+gBBiGC+cC9yPoPCyuB6+zTSWw3v8rgYOSL8U7bE=; b=dGlRhwkvdovIG+Bbl+0NhONN8wjH8gGDFZ4ISj3uXATcepPKyhUYNxwl6plwGEeZWD5Cuh 3po8doBcsZC0fjy9kgw2H6VfVU6ge6QFU1UV5OkLuPyKj6Qlh1NKO0tvnq7nwnxZe9T4er pGLg9pnUl3mkutFdRaq9lz9GozP4jmE= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1709810424; a=rsa-sha256; cv=none; b=7jQt3UZ+ePYWl+RiH9TruaTNNMY84R/Wnpl/OXXzeI1ruIIxv3I8VL8u+esHDdH27CkhO7 MtG0MgDUA6VcRysmVR3GQDt8PQSJTE3ayBTMNX6SAUU/y4UUX69YPpjNju2T9yH+ROzDs8 BqFKDa5uGwLVT74bxgYiZuljcZcP4rk= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=dB1VamwR; spf=pass (imf24.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1709810423; h=from:from: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:autocrypt:autocrypt; bh=T3S+gBBiGC+cC9yPoPCyuB6+zTSWw3v8rgYOSL8U7bE=; b=dB1VamwRTcnIYPFGLgOs7kjpy4rb5yNC4+SZS/goS8W0qgtlzZvT1UnWp81POQaxO1UCRA s/mnbfyJyaFSvgdlgUcpaGhFwK2tZMMOhLNCqAot6CO/TWufgr9KTmganiJ+b+x6oAaxbE AQoppW+1HWDCVXC9yJaRpY6Hrpagk0k= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-627-P_73W1DdPoi1mKrvTRfkEA-1; Thu, 07 Mar 2024 06:20:20 -0500 X-MC-Unique: P_73W1DdPoi1mKrvTRfkEA-1 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-412db67aa46so4373795e9.3 for ; Thu, 07 Mar 2024 03:20:20 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1709810419; x=1710415219; h=content-transfer-encoding:in-reply-to:organization:autocrypt:from :references:cc:to:content-language:subject:user-agent:mime-version :date:message-id:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=T3S+gBBiGC+cC9yPoPCyuB6+zTSWw3v8rgYOSL8U7bE=; b=l/fyse6azIUNXzAMCSuRnHG4hRQ7/VhReGgHKGiKqR8y1StMwZgMjAYf20HaARluDA TtFcSlNO5CdncUFBqBMBsc1c3vmJelzqejvFuDeIIDQRO/suCAqKrrBvZSibgxm3Hj5h Nzb9O/c0LI6q1U96wln7+40EAgtNnP7POUOa9kTY/z06fluKZqFbN+XxUjtoeKrdROB0 B0h/t1PG0bEFDDkTwvSY0gdIYzV/mXssQBvjubKLAGUrSftCUBvvj1kvYJCds/N5N3nq 3n0hV5Qcjzge3XK/4uONVtj1Oz+o7FAFWX9R+hjE5wFBb0RxfOubmIyVarpnVeqWzncZ qZrw== X-Gm-Message-State: AOJu0Yzo44nc0uXBt4K3DiFCbmul4eYDdd9K2oqVbco21GJTz8IpKL1Y uqI9SIDN0rXkUSnMiPHGlo9faO4Po0IjQqbmJlFUyE7WM6W3LKg+OTquiJrfmnWIMdno1S7TbEf jS8RLSFCwkBfxxyr6SVv7ZAczkaK7WgiKPk7Kko/nq9Oos0GM X-Received: by 2002:a05:600c:34d4:b0:412:eddd:12ad with SMTP id d20-20020a05600c34d400b00412eddd12admr5559551wmq.33.1709810419383; Thu, 07 Mar 2024 03:20:19 -0800 (PST) X-Google-Smtp-Source: AGHT+IH5DAdcAYEJic676KLzGOBvUMTYZ0gt2jHmHrLssTtgX9xQo7uLXszebrBAe+xRJuODn/1+lw== X-Received: by 2002:a05:600c:34d4:b0:412:eddd:12ad with SMTP id d20-20020a05600c34d400b00412eddd12admr5559532wmq.33.1709810418997; Thu, 07 Mar 2024 03:20:18 -0800 (PST) Received: from ?IPV6:2003:cb:c74d:6400:4867:4ed0:9726:a0c9? (p200300cbc74d640048674ed09726a0c9.dip0.t-ipconnect.de. [2003:cb:c74d:6400:4867:4ed0:9726:a0c9]) by smtp.gmail.com with ESMTPSA id r7-20020a05600c458700b0041312bdcd6fsm845702wmo.40.2024.03.07.03.20.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 07 Mar 2024 03:20:18 -0800 (PST) Message-ID: <7d9321db-a3c1-4593-91fa-c7f97bd9eecd@redhat.com> Date: Thu, 7 Mar 2024 12:20:17 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] [RFC] proc: pagemap: Expose whether a PTE is writable To: Richard Weinberger Cc: linux-mm , linux-fsdevel , linux-kernel , Linux Doc Mailing List , upstream+pagemap@sigma-star.at, adobriyan@gmail.com, wangkefeng wang , ryan roberts , hughd@google.com, peterx@redhat.com, avagin@google.com, lstoakes@gmail.com, vbabka , Andrew Morton , usama anjum , Jonathan Corbet References: <20240306232339.29659-1-richard@nod.at> <1058679077.23275.1709809843605.JavaMail.zimbra@nod.at> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <1058679077.23275.1709809843605.JavaMail.zimbra@nod.at> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: 1n8pxrgcczymqf4qcgu3pq84qgxore3o X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 91365180008 X-Rspam-User: X-HE-Tag: 1709810424-757157 X-HE-Meta: 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 zjDjuYBO 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 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 07.03.24 12:10, Richard Weinberger wrote: > ----- Ursprüngliche Mail ----- >> Von: "David Hildenbrand" >> But why is that required? What is the target use case? (I did not get >> the cover letter in my inbox) >> >> We're running slowly but steadily out of bits, so we better make wise >> decisions. >> >> Also, consider: Architectures where the dirty/access bit is not HW >> managed could indicate "writable" here although we *will* get a page >> fault to set the page dirty/accessed. > > I'm currently investigating why a real-time application faces unexpected > page faults. Page faults are usually fatal for real-time work loads because > the latency constraints are no longer met. Are you concerned about any type of page fault, or are things like a simple remapping of the same page from "read-only to writable" acceptable? ("very minor fault") > > So, I wrote a small tool to inspect the memory mappings of a process to find > areas which are not correctly pre-faulted. While doing so I noticed that > there is currently no way to detect CoW mappings. > Exposing the writable property of a PTE seemed like a good start to me. Is it just about "detection" for debugging purposes or about "fixup" in running applications? If it's the latter, MADV_POPULATE_WRITE might do what you want (in writable mappings). -- Cheers, David / dhildenb