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 2D042E77188 for ; Mon, 30 Dec 2024 19:32:49 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9760B6B00A8; Mon, 30 Dec 2024 14:32:48 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 926326B00AA; Mon, 30 Dec 2024 14:32:48 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 79F166B00AB; Mon, 30 Dec 2024 14:32:48 -0500 (EST) 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 587CA6B00A8 for ; Mon, 30 Dec 2024 14:32:48 -0500 (EST) Received: from smtpin04.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id CB6911408C0 for ; Mon, 30 Dec 2024 19:32:47 +0000 (UTC) X-FDA: 82952621892.04.57F2650 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf25.hostedemail.com (Postfix) with ESMTP id 23C94A0018 for ; Mon, 30 Dec 2024 19:32:09 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=SvzUW4tq; spf=pass (imf25.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=1735587143; 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=8gSogz0eI5jDLojAcDaPQM/tJrMxplmA5od4oV5Mg/E=; b=nAvIpy49PUfy0ndoe2vdMHq1pxOL38W0tOkqLRgVBKP7YEl3WRvwifKO8b0zGMgu2al+Od LDa33W4NccMme48w3487/N8gqZllThC571maKQhWGNcEt9BZe1tKAJeQA8ngKVw70UkAaK tVEljuiwRLYhQeCOT3UTIF5591gBN34= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1735587143; a=rsa-sha256; cv=none; b=PErnH8fiFexP52S/R8K7DdIxwcz9GlSewJS74Sfd2D0G5zPzAv1R9GBfvuvxWsvPNB4L7y I5UkYreFaneGD+iEFsXN+Ln7i6wM21Uof9tTRNMuZ7aykOTfGl2g/1ZouwbpvkqA2KpnJ+ 4oDiGSHnb1Qoj5lwi9dFV/9ouqR7cj0= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=SvzUW4tq; spf=pass (imf25.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 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1735587163; 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=8gSogz0eI5jDLojAcDaPQM/tJrMxplmA5od4oV5Mg/E=; b=SvzUW4tqR6YCxZd3M3o0GE/wk9lGOXESC7oewLVj1lK3dePeBsNdWvkiZ5LjaFJeod1oTv vJh95+QCnlYHWqckEiMV+SRvUlOml6vy/t3rDe8TdNwOlztiLDt7T125U846v3zbnD1ZID +fNSbSsFMyiF81u5RM2SLiMQP10vKTc= 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-352-eN_aNrmVPHWvij2Xm2KiHA-1; Mon, 30 Dec 2024 14:32:41 -0500 X-MC-Unique: eN_aNrmVPHWvij2Xm2KiHA-1 X-Mimecast-MFC-AGG-ID: eN_aNrmVPHWvij2Xm2KiHA Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-4361ac8b25fso53379145e9.2 for ; Mon, 30 Dec 2024 11:32:41 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1735587160; x=1736191960; 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=8gSogz0eI5jDLojAcDaPQM/tJrMxplmA5od4oV5Mg/E=; b=VDWvG+jQrkyNVYuso/HF2ZUGBWmpn6fN1fi5KtqCpaJsX1m65DCn8/PCJerxPzH2H6 Ww6XfRsdXpuwyyzKo3b9o6d7I9d6XfeNC5CVExX7YVDBaFXycWYMsAGQ7Br7gmjrclcQ a181BDSqUWoQdSEqJCQw2HXjyhAjpPI/BOhMlXZtC4qttwb1EqZ8pm6BKSKR/lqJmECV HWChj+u32kqI6uCN5hwwDJklT5Mk0uBvqkO4Xp/2PZNR09eHeIj2IAg/ptzLbOmGzml8 /7NPkERQX5/q4lxRhYGhWHa404QYFY3eU/cfVPL8YjiTNjqePHVCWUsS3PwjZatK918h kpig== X-Forwarded-Encrypted: i=1; AJvYcCX7rNYieowCkYcfmoZcgqfDWqUd6meUJGzb3vYpPuZVPV/bAweZ0bNT8AAhe2WchSLWHnl6a4IgZw==@kvack.org X-Gm-Message-State: AOJu0YwnllpqQaT5j8ZMcpbRtrybad04vKipbEGeb2hvFJquSfDywtL7 i5FjJispw3C7Uc7MF4tRHzPdZHFMyQxKvQ7XVMFXVlTAaKiFqg/TII4J1mixA8B3JHWCLXykmtW TSb2dKXSllUSrrjdHlEVp0HR1UsXSOw0hqVxVVdrWQsmzGbwGahVOmDjMUdQ= X-Gm-Gg: ASbGnct1oSguazfZboiGx+hrJvoHbZ5iNTF5V0nC9Sk+vdts5DyiShi8PohnU13tVN2 oZXVOtIpcn9Tju3tG0MB5rkLgwkaK0BQW6bExTkjiMXDY9taeYY3dh/GFv1/5zy46AnL8MqA3G5 kYiqkDnXfLo3Tzf4g0fxfnRYSnOO9GDs/PpjAuTGcWaDraA4ti/tRSINssobW+pkl3dDbPf/bcI oByCPJM1nhjBMwVvl9ff5WD21r+8pYd/VsRPBrO02x/iZ9GJcW/4JhZc5WTJN/LG101nPfJ/yqF 9LBUX2qaKc36/UtoxVH6XrSAcI0cuMeUhONu44QtQ4hUvfbyUEzszdzvSQeH+Ov3VVqT5xshxNR F6W9f1677 X-Received: by 2002:a05:600c:350c:b0:434:a91e:c709 with SMTP id 5b1f17b1804b1-43668b78c11mr247248105e9.28.1735587160407; Mon, 30 Dec 2024 11:32:40 -0800 (PST) X-Google-Smtp-Source: AGHT+IGXMdRRTbkzfXC52jO1Asm2TofNSMI1jHlmS65QVbMG0sBt2B2WZwMBhmNpfqVPDvr8Ut3lGg== X-Received: by 2002:a05:600c:350c:b0:434:a91e:c709 with SMTP id 5b1f17b1804b1-43668b78c11mr247247985e9.28.1735587159996; Mon, 30 Dec 2024 11:32:39 -0800 (PST) Received: from ?IPV6:2003:cb:c718:5800:c745:7e74:aa59:8dbe? (p200300cbc7185800c7457e74aa598dbe.dip0.t-ipconnect.de. [2003:cb:c718:5800:c745:7e74:aa59:8dbe]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-436611ea47asm364432485e9.4.2024.12.30.11.32.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 30 Dec 2024 11:32:39 -0800 (PST) Message-ID: Date: Mon, 30 Dec 2024 20:32:37 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: All MADV_FREE mTHPs are fully subjected to deferred_split_folio() To: Barry Song <21cnbao@gmail.com> Cc: Lance Yang , Linux-MM , Ryan Roberts , Baolin Wang , Andrew Morton References: <142a47b6-ac31-465c-917e-7b2e98fddb2f@redhat.com> <8690de27-a1be-4440-a2d6-1a5cc56dcceb@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: rLMdHBnhn05DSXOWTK7h-LMpj2f2gNJeIxxWqiyOCMk_1735587160 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 23C94A0018 X-Stat-Signature: ofjfdaiw3za9oadbftpudxupowxonu67 X-Rspam-User: X-HE-Tag: 1735587129-984686 X-HE-Meta: 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 AqbTeazJ iMbTLGMwTkCOy7MHP0KA7kES9qoFDJGWJRNWxLnj/rthFamUtjAABKF5IPFunDkuUIKIHcbXfNJ32tTvYgpEzI/mBa+WEcEvi6Utl56Z6lAQ/dPuttVVolwRcCLyIIEYwHcolyHPhdvOje6LhpySGieGRdHD5Dw1l0/E1AtWXwtyFLquspV3e4RZynSg9CjSxi8TDltNNWedQE2XuFjUmYdAki7IaP1CnUo0duXPtXN4ycmWqN2fDmgniB5fVSOBfXEVIOQgRthwubIlhW9LRrivI9FiLzYxC3IgNNrMa1qczAmKqrq1gPv4Upf7XVcVGHUTllsdnitkOS5uChuK/Pkj/pHtmVWniq8Fmya9+2fujUwRotB8lrTzul1vMSUb4nQOvrbT801/H07kcmivVChiISahYG2lVqzTwFv/c/ZKxWWyGvM2nZanXTw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000263, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: >> goto discard; >> > > I agree that this is necessary, but I'm not sure it addresses my > concerns. MADV_FREE'ed mTHPs are still being added to `deferred_split`, > and this does not resolve the issue of them being partially unmapped > though it is definitely better than the existing code, at least folios are > not moved back to swap-backed. > > On the other hand, users might rely on the `deferred_split` counter to > assess how aggressively userspace is performing address/size unaligned > operations > like MADV_DONTNEED or unmapped behavior. However, our debugging shows > that the majority of `deferred_split` counter increments result from > aligned MADV_FREE operations. This diminishes the counter's usefulness > in reflecting unaligned userspace behavior. Optimizing that is certainly something to look into, but the bigger issue you describe arises from bad handling of speculative references. Just imagine you indeed have a partially-mapped anon folio and the remaining pages are MADV_FREE'ed. The problem with the speculative reference would still apply. > > If possible, I am still looking for some approach to entirely avoid > adding the folio to deferred_split and partially being unmapped. > > Could the concept be something like this? Very likely it's wrong, because you really have to assure that that folio range is mapped here. Proper folio PTE batching should be applied here -- folio_pte_batch() etc. That can please the counters in many, but not all cases. Again, maybe the deferred-split handling should be handled differently, and not synchronously from rmap code. I see 3 different work items 1) Fix mis-handling of speculative references 2) Perform proper PTE batching during unmap/migration. Will improve performance in any case. 3) Try moving deferred-split handling out of rmap code into reclaim/ access-bit handling. -- Cheers, David / dhildenb