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 D59A1C27C53 for ; Fri, 7 Jun 2024 06:59:27 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E4F136B0095; Fri, 7 Jun 2024 02:59:26 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DFF076B009B; Fri, 7 Jun 2024 02:59:26 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C797A6B009C; Fri, 7 Jun 2024 02:59:26 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id AA9D16B0095 for ; Fri, 7 Jun 2024 02:59:26 -0400 (EDT) Received: from smtpin22.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 536FC814E3 for ; Fri, 7 Jun 2024 06:59:26 +0000 (UTC) X-FDA: 82203191532.22.51C3D60 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf24.hostedemail.com (Postfix) with ESMTP id 12E6418000A for ; Fri, 7 Jun 2024 06:59:23 +0000 (UTC) Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=heC0L8Ww; spf=pass (imf24.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 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=1717743564; 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=JaQjx0mWk+VRsa/TdpIf8VUt+2rOLqlpDyn02y/765g=; b=6zzzac2KLZWK2rlUx8vHx22GOm4ZYQg9K4UitVH8ymD2Ac5AwHkZdwLBLUms/uR/vh65Ld h7RDNb3wcJpCAUbH4Sgd8lAYF9hw16pVBoFbaJmlJA5LqUqIAWYIeSzQpgY41LUtk6QTe/ mH7ujHABytuttf7KAIve4OLl8sAPJfc= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=heC0L8Ww; spf=pass (imf24.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1717743564; a=rsa-sha256; cv=none; b=408ErtCRXWt4obpJLWKYpVezvDTSjCfh4PI9OQa4oAo+dXI217Q/0wV0XYTmD0MzwwTCeq LZieFnJu13g8PI2WnDAUhZBwVqk1j0uM+NmEo+oO2pqovlvaIaRr8q3azVqtyBXUnxzEFe CACzuxgvmiV4k1LSO0l6b+rekwzgq4Q= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1717743563; 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=JaQjx0mWk+VRsa/TdpIf8VUt+2rOLqlpDyn02y/765g=; b=heC0L8WwylrAb+FQHvhIvHzjuDP76xPF34m4q4jw3n1lWk3MT+3dWM8+P8yE//n3+JWtFN x49iA5dtrASvqQkmdZ9Z/ZuAZaE/e+BYWgVb019ISQ0Osg28+uyUqJxVfnz5qPHg3t+K1R WMDQIJoMF6xZSC24oAQG6e87FwteyqQ= 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-220-bUVChnpzPpi0eCepjV0gWA-1; Fri, 07 Jun 2024 02:59:21 -0400 X-MC-Unique: bUVChnpzPpi0eCepjV0gWA-1 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-42156af89afso13732725e9.0 for ; Thu, 06 Jun 2024 23:59:20 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1717743560; x=1718348360; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=JaQjx0mWk+VRsa/TdpIf8VUt+2rOLqlpDyn02y/765g=; b=lDS+u41fUM7HhE+wMqmNjz76FozeY7dvEBCc6xZbnJ/bgEPb5p1ogqq4TSFKWdgyvm 1OxIHdmLFY5c+En2NVoH9qHfWh9yXvsS5lz+vX13Fl2/EA/f5+t0YdQBtnwhzAa/Yiqw gvOuHuwoO6iVH5BLewi8FvrS8BYjzVYudmcOIbNigIBCNDsPC1/iEEf11vvDSS2H7ss4 kRf1lIdX6qCdnDHulWI6i6fXQt8zOMMv3TjGdOhjZeeNv3mFXa5hWO6Tl941KHTjTErg fGzqXtc1u1bMwGnXbvOYZy0JzS96pQbig5lujKYxMHsT1yKvTS5YE7rwC5Y3Ws7soBXh iLQg== X-Gm-Message-State: AOJu0YxApCz2P20/baBfxuuYhBT9biVaT8BK6apW79PAwEKRauJNZuOU SLgi2wQi0NPIHzDiWtif0kDB6QthynAtKp7O8culMT7JnAC+b0cQRVJG1eAdFd3KpaCY3t4gkCJ WEzTHg1IAKth+GQ9VZDCvTbqpOhbFRdIgR75348UA6GkjsmcK X-Received: by 2002:a05:600c:4fd6:b0:420:177f:c2a6 with SMTP id 5b1f17b1804b1-42170b76b86mr4720425e9.10.1717743559788; Thu, 06 Jun 2024 23:59:19 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHdhkU2BmWZH1MLCRzbrKir7vEOh1g4+0ZASNGbFfC6Xq2sKZSbgL8qZa0B3FVXn6ImhXIEvg== X-Received: by 2002:a05:600c:4fd6:b0:420:177f:c2a6 with SMTP id 5b1f17b1804b1-42170b76b86mr4720285e9.10.1717743559326; Thu, 06 Jun 2024 23:59:19 -0700 (PDT) Received: from ?IPV6:2003:cb:c71a:2200:31c4:4d18:1bdd:fb7a? (p200300cbc71a220031c44d181bddfb7a.dip0.t-ipconnect.de. [2003:cb:c71a:2200:31c4:4d18:1bdd:fb7a]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-42158110dfesm79268945e9.19.2024.06.06.23.59.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 06 Jun 2024 23:59:18 -0700 (PDT) Message-ID: <502bb09f-ea09-451b-8473-48b14dd2f554@redhat.com> Date: Fri, 7 Jun 2024 08:59:17 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: Unifying page table walkers To: Matthew Wilcox , Khalid Aziz , Peter Xu , Vishal Moola , Jane Chu , Muchun Song Cc: linux-mm@kvack.org References: 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: 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: 7bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 12E6418000A X-Stat-Signature: zsekz1z36niijcu9ktrdk1xm8yf76wx1 X-HE-Tag: 1717743563-122683 X-HE-Meta: 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 jnlw/hEN 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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 06.06.24 20:29, Matthew Wilcox wrote: > One of the things we discussed at LSFMM was unifying the hugetlb and > THP page table walkers. I've been looking into it some more recently; > I've found a problem and I think a solution. > > The reason we have a separate hugetlb_entry from pmd_entry and pud_entry > is that it has a different locking context. It is called with the > hugetlb_vma_lock held for read (nb: this is not the same as the vma > lock; see walk_hugetlb_range()). Why do we need this? Because of page > table sharing. > > In a completely separate discussion, I was talking with Khalid about > mshare() support for hugetlbfs, and I suggested that we permit hugetlbfs > pages to be mapped by a VMA which does not have the VM_HUGETLB flag set. > If we do that, the page tables would not be permitted to be shared with > other users of that hugetlbfs file. But we want to eliminate support > for that anyway, so that's more of a feature than a bug. I am not sure why hugetlb support in mshare would require that (we don't need partial mappings and all of that to support mshare+hugetlb). The possible mshare directions I discussed with Khalid at LSF/MM would likely not need that. But I have no idea which mshare design you and Khalid are discussing right now. Maybe it would be a a good idea that the three of us meet to discuss that, if my feedback/opinion could be helpful. > > Once we don't use the VM_HUGETLB flag on these VMAs, that opens the > door to the other features we want, like mapping individual pages from > a hugetlb folio. And we can use the regular page table walkers for > these VMAs. Right, but to me that's a different, long-term project that mshare would maybe not have to rely on. -- Cheers, David / dhildenb