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 988F5C27C53 for ; Fri, 7 Jun 2024 07:15:23 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 279D76B009E; Fri, 7 Jun 2024 03:15:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 229556B009F; Fri, 7 Jun 2024 03:15:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0A30B6B00A0; Fri, 7 Jun 2024 03:15:23 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id E23926B009E for ; Fri, 7 Jun 2024 03:15:22 -0400 (EDT) Received: from smtpin27.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id A50B5A1BEE for ; Fri, 7 Jun 2024 07:15:22 +0000 (UTC) X-FDA: 82203231684.27.E5E53BA Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf05.hostedemail.com (Postfix) with ESMTP id 723C0100018 for ; Fri, 7 Jun 2024 07:15:20 +0000 (UTC) Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=f8FcbOz+; spf=pass (imf05.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=1717744520; a=rsa-sha256; cv=none; b=29kHTnkQeIEL5qJZANDO7cPXw3QmQj/sC0lILy2KGQVq9/8n81PahKKCkSMtFdMrleJczc JiggfRz80XqOU7o/CCaJDZCF6V6iab7023nTIujl2THmghWYtj1LvzcPlx0VlcA21uuVvq +dZJ0PFunRl7e5gGi/Uz9b/4HxIdMXY= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=f8FcbOz+; spf=pass (imf05.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=1717744520; 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=NS2CX2hp/KfU9CpiW1auYDWZVfB9JslO2rUm8IhP77g=; b=akRDiLe5Lc79jY4ApH1w5wxOYyK/6WVVoSitvenakfK2rKolxiXwZe3leCw7NWOxNLhgBb bZuAXeIiNfYbftwk9ry9YkMwTEE3HM1l9Z8PMzeSNKbda447tDTrAQhK/FoA0TZ4CKlbBj wv5aj2/0A3ju4Sf0IkkBX+qHTEQEgQ4= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1717744519; 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=NS2CX2hp/KfU9CpiW1auYDWZVfB9JslO2rUm8IhP77g=; b=f8FcbOz+Vc+4N+rdojmUIS+s0NLQ26OXONTeqAMZDW0+6Qwz1FSiRECM3TLRySjit3iei/ psMyOlvTozie5koV78QhhLn/M7Ge3lAqUul8PreP98lqqbnsDma9+nAT8np9fW9hE0aWYj RFEuiMvGq6SoOQ8O5mGHfhRctef/rmc= Received: from mail-wr1-f71.google.com (mail-wr1-f71.google.com [209.85.221.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-460-kyLkFfGEPTSaaf2sxj0q9Q-1; Fri, 07 Jun 2024 03:15:18 -0400 X-MC-Unique: kyLkFfGEPTSaaf2sxj0q9Q-1 Received: by mail-wr1-f71.google.com with SMTP id ffacd0b85a97d-35e0ea8575cso1122252f8f.3 for ; Fri, 07 Jun 2024 00:15:18 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1717744517; x=1718349317; h=content-transfer-encoding:in-reply-to:organization:autocrypt:from :content-language: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=NS2CX2hp/KfU9CpiW1auYDWZVfB9JslO2rUm8IhP77g=; b=GSBqY/1zbj+wLYRQfrDZBzA0uY471ureF/2wRBeWB6ij29yD0Te9DtLAYc4AnwsNSN QAfaUbDF6EhGl3n2pysHxKZGTl22ddcVlQlcfgd8TN8WdLznxkJBNFWzvnP6JDaVPsBk 9iyxo/fiVQeIkcY57O5oh+71x7H7+/z1/UKba9IugxVqaX/gHve+1/YxBu11NF9U+dzm JkgJe3+G/aB0fRd9mSyOcyWcqropcHtGo+3y8qMBjjbsJ91dKGIkR7q4HsAdPC3zBxF6 apesBNXsnpcT65vWJgK5KSwxUJmGtIoOJnS5fFR5AO67LrmIFMbhp+Pi0csLT+SB9A0F PcLQ== X-Forwarded-Encrypted: i=1; AJvYcCVWbi+pPadKwZ5sRMSL3llSkXB84tlh9P2QcHbQBpCPGK8/SKra9YjSljqQ1cLz4nZ/u8+ggfBJajTRhGaiP21yIgA= X-Gm-Message-State: AOJu0YywSsMFKjiBVa6eVVZpiPzncz6LOlkUHPn+FD6y3sv+V/bBPjv2 XXSCVz0btfFkp8ProR3OLmnGNOzRmOxRnvwalpV8qql43TIrdP/5jXqgrO++SKehnWm6RSElDSi 4Cdw0haJwsXyA+qbh8JwOHM9GaQcdXSHsbeYJb7CIEdd31X8D X-Received: by 2002:a5d:5686:0:b0:354:fb1d:694e with SMTP id ffacd0b85a97d-35efed64b39mr1297375f8f.29.1717744517260; Fri, 07 Jun 2024 00:15:17 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFASGSJLmyEFk+qZ2HBy/f4ICVeGE02ufPBZvvBdr4zrkDeQILcAwmEWzuYzRpEUsgwEIqP/g== X-Received: by 2002:a5d:5686:0:b0:354:fb1d:694e with SMTP id ffacd0b85a97d-35efed64b39mr1297353f8f.29.1717744516852; Fri, 07 Jun 2024 00:15:16 -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 ffacd0b85a97d-35ef5d4d521sm3344236f8f.47.2024.06.07.00.15.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 07 Jun 2024 00:15:16 -0700 (PDT) Message-ID: <45a47fdd-f22b-42fb-b515-639b9ca6129e@redhat.com> Date: Fri, 7 Jun 2024 09:15:15 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: Unifying page table walkers To: James Houghton , Matthew Wilcox Cc: Khalid Aziz , Peter Xu , Vishal Moola , Jane Chu , Muchun Song , 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: 8bit X-Rspamd-Queue-Id: 723C0100018 X-Rspam-User: X-Rspamd-Server: rspam12 X-Stat-Signature: ifost555pm6t1p3h63cnqk63ka1ksrn5 X-HE-Tag: 1717744520-502636 X-HE-Meta: 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 1xY55zwQ 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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 07.06.24 01:07, James Houghton wrote: > On Thu, Jun 6, 2024 at 2:21 PM Matthew Wilcox wrote: >> >> On Thu, Jun 06, 2024 at 01:23:08PM -0700, James Houghton wrote: >>> On Thu, Jun 6, 2024 at 1:04 PM Matthew Wilcox wrote: >>>> Right, so we ignore hugetlb_fault() and call into __handle_mm_fault(). >>>> Once there, we'll do: >>>> >>>> vmf.pud = pud_alloc(mm, p4d, address); >>>> if (pud_none(*vmf.pud) && >>>> thp_vma_allowable_order(vma, vm_flags, >>>> TVA_IN_PF | TVA_ENFORCE_SYSFS, PUD_ORDER)) { >>>> ret = create_huge_pud(&vmf); >>>> >>>> which will call vma->vm_ops->huge_fault(vmf, PUD_ORDER); >>>> >>>> So all we need to do is implement huge_fault in hugetlb_vm_ops. I >>>> don't think that's the same as creating a hugetlbfs2 because it's just >>>> another entry point. You can mmap() the same file both ways and it's >>>> all cache coherent. >>> >>> That makes a lot of sense. FWIW, this sounds good to me (though I'm >>> curious what Peter thinks :)). >>> >>> But I think you'll need to be careful to ensure that, for now anyway, >>> huge_fault() is always called with the exact same ptep/pmdp/pudp that >>> hugetlb_walk() would have returned (ignoring sharing). If you allow >>> PMD mapping of what would otherwise be PUD-mapped hugetlb pages right >>> now, you'll break the vmemmap optimization (and probably other >>> things). >> >> Why is that? This sounds like you know something I don't ;-) >> Is it the mapcount issue? > > Yeah, that's what I was thinking about. But I guess whether or not you > are compatible with the vmemmap optimization depends on what > mapcounting scheme you use. If you just use the THP one, you're going > to end up incrementing _mapcount on the subpages, and that won't work. > > I'm not immediately thinking of other things that would break... need > to think some more. If we're only concerned about unifying most page table walkers there is little reason to mess with mapcounts of hugetlb at this point. mapcounts with hugetlb only come into play once we support partial mappings, and I consider that yet another step (mapping/unmapping code) than unifying most page table walkers like Oscar+Peter have on their plate. -- Cheers, David / dhildenb