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 D4881C47DD9 for ; Wed, 28 Feb 2024 09:34:12 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 68FD86B00A7; Wed, 28 Feb 2024 04:34:12 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 640A4940007; Wed, 28 Feb 2024 04:34:12 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4BAB26B00A9; Wed, 28 Feb 2024 04:34:12 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 3C3B56B00A7 for ; Wed, 28 Feb 2024 04:34:12 -0500 (EST) Received: from smtpin06.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 0C67F40F1A for ; Wed, 28 Feb 2024 09:34:12 +0000 (UTC) X-FDA: 81840701544.06.DB9D089 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf27.hostedemail.com (Postfix) with ESMTP id E1B2240006 for ; Wed, 28 Feb 2024 09:34:09 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=Mmjy6xO5; spf=pass (imf27.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=1709112850; 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=paHRAJ44zReBwEf+4/MpQO07yBq5PB+a0frjdqqTm0E=; b=ir2Av8MtQjnh6/g6/knnnD/jiFFPWp0Xo/nGb0xoKuv1W1vyhDTomCVdg/ZOooI1Pq2V6O E1DJnT3qvBZHlWE8v5QQYy9R2ahRFKNqf28FtaoVHKwchxaas81syEt5kNJU5eAY1dzlu5 gEalb/Z09bPL4Ev+qbp5Lepa93cp250= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1709112850; a=rsa-sha256; cv=none; b=h2mOmvC2ZGzaD4qpSLAt3PgGJTv5VjEe9PaNnVHBES6EybFfOMllWW9lOEMIUkCqCaL9g/ 6qnJnlhmsPX5xK3lUrpO/BwDKgx2vTnt3fivq9JVk4SXAYTmhy7wySxnyzpDI+ytbZRVg9 3GPJF6bV0BdRXQE281Onl6Xh4uuA/lc= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=Mmjy6xO5; spf=pass (imf27.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=1709112849; 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=paHRAJ44zReBwEf+4/MpQO07yBq5PB+a0frjdqqTm0E=; b=Mmjy6xO5/jbhbkQW4yZxGYOsOso5rxXz5iPu46//UU7ekYn9MexdK02rF1KleF7rgj9tPY 9u2wjLdPMpoWS1eNn2F7UL74ZiaCg0WMrrON6ObqC9e2IaXWtmF9UV6fWYyJ7TkA9Zlcbm FkdDa/hA+rO+a2FEj2Mva4M04glM92g= Received: from mail-ed1-f70.google.com (mail-ed1-f70.google.com [209.85.208.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-486--23Na3TTOyKGjbFYj5nJ5Q-1; Wed, 28 Feb 2024 04:34:07 -0500 X-MC-Unique: -23Na3TTOyKGjbFYj5nJ5Q-1 Received: by mail-ed1-f70.google.com with SMTP id 4fb4d7f45d1cf-566195392eeso584717a12.0 for ; Wed, 28 Feb 2024 01:34:07 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1709112846; x=1709717646; 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=paHRAJ44zReBwEf+4/MpQO07yBq5PB+a0frjdqqTm0E=; b=hgemimNVGRmUcR9T7KmYnjiSdyHStOHpgO7UH95gvnWwpiNHu5W4eBS9P1q01DH/4Z OFUtkXEgNSPotn5xqJDdz4W6Mf+63l2KwMY8XpTCDKv/uBk9J8A+lS+vJ5doUNnPF5Ms 8GiS+81z6pYrI9NXcqa1R0Px8Aw74ER1zctlIeXJKqmoC6CAZt8Ws6+JYdBkTkp9lz5X Aj2gAK7r7rhQEp0E+VwHdFobS6V2+pVNc8PawL9dzWtdgOlV+qJRujALNESRf0+6McqC WSL+zcrQ3Gc7rl6sosbDzRBJWQ3XnHrrrl1GLnlOx0kemM+hlYde3ivG2kHaYEq9jG7y TIww== X-Forwarded-Encrypted: i=1; AJvYcCWQfh+LkWIybrtJ8GTyUT1ZhzinXGNamrNqPgSoyE00Len8aMqGV7TcYHaLlPDZbdyiTIzI3KqXKoiCkI27XQiWNAI= X-Gm-Message-State: AOJu0YzRvWkZOFjt2fAxyNcs3eKuQdnlXJiC5Gq7/M6TTM8591E9bC2F T1AmZp5t7SBdp3RRFZUKguB2YOBzaWf7Zn5fTUKtxveNS37rmd7prH7QrsrCX5LFaMSzoOR7GMg 0ZvgKZn7E2KtsNEL7qw2aaChjdrfLPYtLCvaVITB14UzIKB2c X-Received: by 2002:a05:6402:4022:b0:566:72b0:286a with SMTP id d34-20020a056402402200b0056672b0286amr762876eda.2.1709112846657; Wed, 28 Feb 2024 01:34:06 -0800 (PST) X-Google-Smtp-Source: AGHT+IHU8C7gERAJhILIISLEBoy8Jl60VJcu/2Dgsco6+wq67tJ/NqqNO3ZzUBw8tfaMzB4vq2zhsA== X-Received: by 2002:a05:6402:4022:b0:566:72b0:286a with SMTP id d34-20020a056402402200b0056672b0286amr762854eda.2.1709112846261; Wed, 28 Feb 2024 01:34:06 -0800 (PST) Received: from [10.32.64.237] (nat-pool-muc-t.redhat.com. [149.14.88.26]) by smtp.gmail.com with ESMTPSA id x19-20020aa7cd93000000b0056486eaa669sm1610116edv.50.2024.02.28.01.34.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 28 Feb 2024 01:34:05 -0800 (PST) Message-ID: <1d9b85ce-63d1-43b4-a4ad-b9c1d89f952b@redhat.com> Date: Wed, 28 Feb 2024 10:34:04 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 4/4] mm: swap: Swap-out small-sized THP without splitting To: Barry Song <21cnbao@gmail.com>, Ryan Roberts Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.com, shy828301@gmail.com, wangkefeng.wang@huawei.com, willy@infradead.org, xiang@kernel.org, ying.huang@intel.com, yuzhao@google.com, chrisl@kernel.org, surenb@google.com, hanchuanhua@oppo.com References: <20231025144546.577640-5-ryan.roberts@arm.com> <20240222070544.133673-1-21cnbao@gmail.com> <1a9fcdcd-c0dd-46dd-9c03-265a6988eeb2@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-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: E1B2240006 X-Rspam-User: X-Stat-Signature: ur5y3jzdttansb8mfywr56c87xhc4tkj X-Rspamd-Server: rspam03 X-HE-Tag: 1709112849-205428 X-HE-Meta: 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 co3wGyJY 0APxw5pdUK8SGiwoLeM8s5kMkKJdtPwzjWjdaCchB0/5CJFZUx6S/feWXTaA2I1kfh3DbMdo9wn+DQIjJaLqC2zLytAtm1pGecZp548FJHO71pb013KWU/R5xsXYXekW1WqDe7mJlpZguMYKCNtfhsJZOja5avObdwYyhmpp/kh/zXd4= 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: >>>>> >>>>> To me, it seems safer to split or do some other similar optimization if we find a >>>>> large folio has partial map and unmap. >>>> >>>> I'm hoping that we can avoid any new direct users of _nr_pages_mapped if >>>> possible. >>>> >>> >>> Is _nr_pages_mapped < nr_pages a reasonable case to split as we >>> have known the folio has at least some subpages zapped? >> >> I'm not sure we need this - the folio's presence on the split list will tell us >> everything we need to know I think? > > I agree, this is just one question to David, not my proposal. if > deferred_list is sufficient, > I prefer we use deferred_list. > > I actually don't quite understand why David dislikes _nr_pages_mapped being used > though I do think _nr_pages_mapped cannot precisely reflect how a > folio is mapped > by multi-processes. but _nr_pages_mapped < nr_pages seems be safe to > tell the folio > is partially unmapped :-) I'm hoping we can get rid of _nr_pages_mapped in some kernel configs in the future (that's what I am working on). So the less we depend on it the better. With the total mapcount patch I'll revive shortly, _nr_pages_mapped will only be used inside rmap code. I'm hoping we won't have to introduce other users that will be harder to get rid of. So please, if avoidable, no usage of _nr_pages_mapped outside of core rmap code. -- Cheers, David / dhildenb