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 9855CE77197 for ; Thu, 9 Jan 2025 11:22:33 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id CD16A6B007B; Thu, 9 Jan 2025 06:22:32 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id C7FA36B0082; Thu, 9 Jan 2025 06:22:32 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AD28B6B0083; Thu, 9 Jan 2025 06:22:32 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 900796B007B for ; Thu, 9 Jan 2025 06:22:32 -0500 (EST) Received: from smtpin17.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id F3E19160CBE for ; Thu, 9 Jan 2025 11:22:31 +0000 (UTC) X-FDA: 82987675302.17.B44E12B 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 5963B100002 for ; Thu, 9 Jan 2025 11:22:29 +0000 (UTC) Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=YYZ50u8Z; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf05.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1736421749; 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=F7w0Lj+T4CWrVwi5FMFjGb9ZW0o7/x2RrSBvY2OdilM=; b=7A1IUgagmR5UUDZoeDCAaC0pu8Con5bZhWowvH7iLIJ+QykWH+eK+XR6M6d4PJ/x9yslZK 30rQC7zd9IWnJP3+GQb84hSoAYCuZ8LfOmE1MRVOpyu2C+Oy76DOdhtgoBkgy98VxSJq8L hmyEPKzvuvxc4iFmTDyuyUcNrFVso6w= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1736421749; a=rsa-sha256; cv=none; b=Bd98gcD/rQw2A+yMq/PVolYe5zqi6WJwO0KwxzNVqIuEUuQpsFOXyYEYi9ip9AeZ3eTxTa GVmczwk8hSQbbR22CqGzBrbOoFLJFN9WFpzWccT+OpX687HVOemovBUIUL8faOExRcWAW2 1nu47h9OZ4ftnjw0FklEbW3ifNet5v4= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=YYZ50u8Z; dmarc=pass (policy=none) header.from=redhat.com; spf=pass (imf05.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1736421748; 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=F7w0Lj+T4CWrVwi5FMFjGb9ZW0o7/x2RrSBvY2OdilM=; b=YYZ50u8Z3LbIPJede0MEJbzj48HoM3NLKrCLrYVYBre4kjRhl6VMTH+nHKR+hNoUhRHT2S UgNEksIca00I2p759RF86xJqDir0HfOi50F0pEdPZ5YMl2GqsuzH3MVMOFciU8hzUkoChP IPLgnSTa9wQgGFsJwat/YP5xOCqZOdQ= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-510-wZu0mEzEN86uVEhHlJTYDA-1; Thu, 09 Jan 2025 06:22:27 -0500 X-MC-Unique: wZu0mEzEN86uVEhHlJTYDA-1 X-Mimecast-MFC-AGG-ID: wZu0mEzEN86uVEhHlJTYDA Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-4362b9c15d8so4126035e9.3 for ; Thu, 09 Jan 2025 03:22:27 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1736421746; x=1737026546; 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=F7w0Lj+T4CWrVwi5FMFjGb9ZW0o7/x2RrSBvY2OdilM=; b=dMgo6IWhgB4fPriTROtNnGD5c/VxwanOSo0JQl8K2HovUwvGZPB4yYhxtZQrVj/K4Z BAuDquG3EXUdA3WIwIxUCN6oMpWd38KN7HIUYA6xvRAA1XHC2vQcoj92hA4NMAIVI00f O1pgtwOmQ4kN8DSlljFUtQ4X7BlHT4fZBvsQAUaJyWZILlXPM3+5AIhrQB6RvKL/2OPL UsLwTwoXrjzjhI2UmO5nRwOdqD3yvnci/SmKUqIGe0XAzCGSUlzg9hTksTif/ki5yKzf HLHcX0cvSiYmQJeZ0j7aDf86CLvfBOvhQHrjUtuQDMGBEDojut4oF7DorAZ0UIf5+sTL hFJQ== X-Forwarded-Encrypted: i=1; AJvYcCXQAyP/2rDEmDeeFyPkfh486jRei3opL/cs3ElPamKAq0TO3J+2bQd+wak2f4qAOn6CLBMlXLcqWg==@kvack.org X-Gm-Message-State: AOJu0Yy8R07XQbQalAsMNMo4ymdoKER8o3e6a51uUpgJIhSPYzi0cpPN 1fPF0kmCqxmmEHSXRvU5dnuKccwR/AbS4Of/5UZF2VFyvbKHakNBIFtyAxpoHob+n75saiPwTh6 YVUWl/gW1B6YxhahFd4KEv+H4mJhjkRjyTxBs6fPDBFH9z04l X-Gm-Gg: ASbGnctN4LaZTZ63V/N/sNSCOfC97hXXZFLVeKe6wOlnATS74sYTsxfMvYQh2c+Ucbz qrM0tSZGitjIFuNm0xUw+LIG3ljAvFFT7abt1I1LmALCzpSBPSfT6zd8CPMqFeci91TO/iJPWEO 8vkR6cv4L+qtLMhDdqHpZOD/V8UmHbpnyS9nhquhtygSZeIyt3IyXydnysb1FKDdy24449M6D7A w6+/VopXLVMNM1RsciGm3xforCr1AAY9S0SroiZhhBuoHizKp3QNdIsMpsBr2HPY9HJxKs9cZqP kT3HFI5nr9PTDDghBubFG02eldv3L2s7l5IRTFAukk64FNMD3qRgNO98mE77T5AUKQgr039csVj d0G2l0Q== X-Received: by 2002:a5d:64ad:0:b0:385:e67d:9e0 with SMTP id ffacd0b85a97d-38a8730d521mr5145615f8f.29.1736421746322; Thu, 09 Jan 2025 03:22:26 -0800 (PST) X-Google-Smtp-Source: AGHT+IHkPjFLyjd0K3wvAdCPpWhl0J54qBsWSnwpSWDeCcp0szfh4piYX+SHBbgnXJufh3vWMLbm4A== X-Received: by 2002:a5d:64ad:0:b0:385:e67d:9e0 with SMTP id ffacd0b85a97d-38a8730d521mr5145576f8f.29.1736421745831; Thu, 09 Jan 2025 03:22:25 -0800 (PST) Received: from ?IPV6:2003:cb:c72e:800:d383:9661:5934:2cfa? (p200300cbc72e0800d383966159342cfa.dip0.t-ipconnect.de. [2003:cb:c72e:800:d383:9661:5934:2cfa]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38a8e4c1b05sm1528207f8f.88.2025.01.09.03.22.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 09 Jan 2025 03:22:25 -0800 (PST) Message-ID: <1fdc9d50-584c-45f4-9acd-3041d0b4b804@redhat.com> Date: Thu, 9 Jan 2025 12:22:23 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 4/5] mm/migrate: skip migrating folios under writeback with AS_WRITEBACK_INDETERMINATE mappings To: Shakeel Butt Cc: Miklos Szeredi , Joanne Koong , Bernd Schubert , Zi Yan , linux-fsdevel@vger.kernel.org, jefflexu@linux.alibaba.com, josef@toxicpanda.com, linux-mm@kvack.org, kernel-team@meta.com, Matthew Wilcox , Oscar Salvador , Michal Hocko References: <0ed5241e-10af-43ee-baaf-87a5b4dc9694@redhat.com> <446704ab-434e-45ac-a062-45fef78815e4@redhat.com> <791d4056-cac1-4477-a8e3-3a2392ed34db@redhat.com> 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-MFC-PROC-ID: nkW98x-D-rbT_oMzlat8NAmonJWqvUC0nAInFA7CSTs_1736421746 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: gcp486g3umnas9xkzyomss9jhp35bbqe X-Rspamd-Queue-Id: 5963B100002 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1736421749-807520 X-HE-Meta: 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 86e4sQgT 4PsXnTsJ0FW3ZbrWh1hApCy1gsHHKAvVnZnY4t5F0f33MLbwUjGOVUTgbWhEaWuskhGYLz64z7l8UYI9K6pay1SQmcxuHMK5jFviPXJN8aypLOfwq4CUFozIjU1wGjDB7ED/EUEVWgJo9ZjAJNGLxXb5khndtjdkieKNvpYeVdkJp8Nf7GZ6BwnByHZevf+5Srg0OPZvhr5AtLanIKyaeZuyGixvSkZ9wJ66Dp9iBXJxvZrV0dqbqyYz61SwXakcS7QGVZ/Nn3qvmd2eWt3lmQ7BI1a6ESn1qFk/PSzpVSIx/4jN8UwuweifdJh8vFE/5QemDOiaUrbOtFIOqIw5tijhYG0sd1XbhRJMhTdSmceraL1s9O745jONhbUgln63qOEunJa8UXC83ycT/3xoCn39531bfTciN41Rn+A3T7W0eaKEIdGyhLEaAo2pUR85LZJ3MrgbfkPlHWfsuUs0DD3HPJw== 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 07.01.25 19:07, Shakeel Butt wrote: > On Tue, Jan 07, 2025 at 09:34:49AM +0100, David Hildenbrand wrote: >> On 06.01.25 19:17, Shakeel Butt wrote: >>> On Mon, Jan 06, 2025 at 11:19:42AM +0100, Miklos Szeredi wrote: >>>> On Fri, 3 Jan 2025 at 21:31, David Hildenbrand wrote: >>>>> In any case, having movable pages be turned unmovable due to persistent >>>>> writaback is something that must be fixed, not worked around. Likely a >>>>> good topic for LSF/MM. >>>> >>>> Yes, this seems a good cross fs-mm topic. >>>> >>>> So the issue discussed here is that movable pages used for fuse >>>> page-cache cause a problems when memory needs to be compacted. The >>>> problem is either that >>>> >>>> - the page is skipped, leaving the physical memory block unmovable >>>> >>>> - the compaction is blocked for an unbounded time >>>> >>>> While the new AS_WRITEBACK_INDETERMINATE could potentially make things >>>> worse, the same thing happens on readahead, since the new page can be >>>> locked for an indeterminate amount of time, which can also block >>>> compaction, right? >> >> Yes, as memory hotplug + virtio-mem maintainer my bigger concern is these >> pages residing in ZONE_MOVABLE / MIGRATE_CMA areas where there *must not be >> unmovable pages ever*. Not triggered by an untrusted source, not triggered >> by an trusted source. >> >> It's a violation of core-mm principles. > > The "must not be unmovable pages ever" is a very strong statement and we > are violating it today and will keep violating it in future. Any > page/folio under lock or writeback or have reference taken or have been > isolated from their LRU is unmovable (most of the time for small period > of time). ^ this: "small period of time" is what I meant. Most of these things are known to not be problematic: retrying a couple of times makes it work, that's why migration keeps retrying. Again, as an example, we allow short-term O_DIRECT but disallow long-term page pinning. I think there were concerns at some point if O_DIRECT might also be problematic (I/O might take a while), but so far it was not a problem in practice that would make CMA allocations easily fail. vmsplice() is a known problem, because it behaves like O_DIRECT but actually triggers long-term pinning; IIRC David Howells has this on his todo list to fix. [I recall that seccomp disallows vmsplice by default right now] These operations are being done all over the place in kernel. > Miklos gave an example of readahead. I assume you mean "unmovable for a short time", correct, or can you point me at that specific example; I think I missed that. > The per-CPU LRU caches are another > case where folios can get stuck for long period of time. Which is why memory offlining disables the lru cache. See lru_cache_disable(). Other users that care about that drain the LRU on all cpus. > Reclaim and > compaction can isolate a lot of folios that they need to have > too_many_isolated() checks. So, "must not be unmovable pages ever" is > impractical. "must only be short-term unmovable", better? > > The point is that, yes we should aim to improve things but in iterations > and "must not be unmovable pages ever" is not something we can achieve > in one step. I agree with the "improve things in iterations", but as AS_WRITEBACK_INDETERMINATE has the FOLL_LONGTERM smell to it, I think we are making things worse. And as this discussion has been going on for too long, to summarize my point: there exist conditions where pages are short-term unmovable, and possibly some to be fixed that turn pages long-term unmovable (e.g., vmsplice); that does not mean that we can freely add new conditions that turn movable pages unmovable long-term or even forever. Again, this might be a good LSF/MM topic. If I would have the capacity I would suggest a topic around which things are know to cause pages to be short-term or long-term unmovable/unsplittable, and which can be handled, which not. Maybe I'll find the time to propose that as a topic. -- Cheers, David / dhildenb