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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 693CDC7EE2A for ; Wed, 25 Jun 2025 16:57:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=HDYmk8nUIEBllr11u7gZCCbXSbBQzHOYE0IyCu7JXpA=; b=vEl1UnnwgOlYzmuvj+w+39SRo2 K3UttgKUShZR/S8nJcg6HPbR/uWu8aOT1KzriFk/0wTXzjuUHeNj4alK0UgzalzxtTJA6N0plXT3q ZEMLNlK38f55g1eFa8NxFi6/qN1jJhoucTfbGUhV7mtwrBf05HBGD8lh9QnR47svmLv0PvrsRV7Ds lyk8nomcj0gf/VnIJwQcAT09Couz+U5+oze41Hb2Oc5GlJZdLC0jmg1lsq00MrWXOqLofkG8UoxyW h8ORpMlyBR9ukDWVNSNo+4RGX+xwCtfIgjeR78C7CVWymFojN5Www0cLYmvoXtO95sbbMjz5+794v BpICi+Cw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uUTQy-00000009OhL-39lQ; Wed, 25 Jun 2025 16:57:16 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1uUPBz-00000008cM4-0k8D for linux-arm-kernel@lists.infradead.org; Wed, 25 Jun 2025 12:25:33 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1750854330; 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=HDYmk8nUIEBllr11u7gZCCbXSbBQzHOYE0IyCu7JXpA=; b=ByeRLj+cZMuGL11Ux263XpTEqvcmGchdw0SCMrEfspOgk6F6HDKQZTk1bWP5YnEVUI/P5T +LhrkQchz3MnGWwFSZJ4rfxeKtvzG19tpONqVFRSZkXZAwCZ8BpO+M4VYRoPgJUOedCSut 1ggR2yzsHFMjyRQz1jKvKyuT8NyKcsU= 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-695--g7N0b69N1itJypjaIN3gw-1; Wed, 25 Jun 2025 08:25:28 -0400 X-MC-Unique: -g7N0b69N1itJypjaIN3gw-1 X-Mimecast-MFC-AGG-ID: -g7N0b69N1itJypjaIN3gw_1750854328 Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-450d50eacafso11177575e9.3 for ; Wed, 25 Jun 2025 05:25:28 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1750854328; x=1751459128; 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=HDYmk8nUIEBllr11u7gZCCbXSbBQzHOYE0IyCu7JXpA=; b=T+Kb8VhApck6WBCWfKIMY5yVUxl5t73mYBR4rqTqSDqxYbkiWhk79RQ/jTOiauoZ2m zQ7ROBKQEqga3OhXCmOQ78ohyPNm/F6ub8zD7ThCp7gsJwNtnQxL3eUBgHPsE+vfAgeQ 9VFxYXY0tJohEDA0EZWuZRiGFjJEXVw2iKQ2UEs75Ui9G0ZPCBww24bPLEF7haVqPl1e CyF+XzmBe6iTpJIUqJVOiAQXAxTHHz3vs77GlDnDP/TTpE4fx77mRTCOXxqzP/fFXiSA 7p+GIgPon3rP+mXEPeclLbwLltk/FLSoqOOfQG/p+XtbLbv+412v5l+RykD9a5IptTZj B/Ng== X-Forwarded-Encrypted: i=1; AJvYcCXq8VohCoQCyF5sE6gdIuYd2S2BF642ruWGQUyHc5eFt+KB1HKo9kcddna8m2is1UGlXGPLASVxa4KPN5ugsDDl@lists.infradead.org X-Gm-Message-State: AOJu0YzpQ1XnWYsdViVGZ1LVD5y8LiMAwfyDRXmC8t9ERWvTq5MCO5Wb WNtWu/OFDgDflSM0puZJEbJh5wCeSr5XLqSzJkiYQUp8DNkqNplJ48a40H0JUK3W1TCJIkpWus3 21u5qSPis4XWYJCbX3E9t5jhcE0hVojg/CKDsYvx5c5TzoZxpyyxJX++yo8jsPQOhj3CUVpckVA Eb X-Gm-Gg: ASbGncs/rbf8zo8bOZE7tgvkpKt4zAuK2HG2NaGri3AWfKjhlHDyCTQ4kOH+FA5LTUq 2+OSi3K2xEzUGq79lxyt9Vd8Cz3BcYGA/ZLIRQJ0exn5yudlXeG41XvnH+14mQhLx6GRpZsJI2q cN9CZZ44kOZz/3zet2tflj1wlIqMFTZnITurC0Uyl4Y2qXEQHW1G/QpyIIgPmG8ZsJCLU1XaCPO kWX3edaQ6GnnM3ovT0wgoHumc7TOpg1391YVYRZaUsSxmY99C+pLoynsI6BN7280Um3gs7EKheL f73QDZRhbphi25BrnSlmW0z+8JlnWS0mt6jRZvTCmjEABMceYUW29CQTV7+BdBHd/lBxHKF4HST wYa5IHwYUUN4Ws71e8tVK/oIMDuUuyif3+/tnzgLLtHn3 X-Received: by 2002:a5d:59c5:0:b0:3a6:ec41:b9df with SMTP id ffacd0b85a97d-3a6ed64c0b6mr2122594f8f.49.1750854327715; Wed, 25 Jun 2025 05:25:27 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFzzn1jUnDPQBJAUUttMGYVvx0eT64PRI60IqxVI+7ZhvAx6ZiMuZPeCNf6yzmjyKxVSvIBOw== X-Received: by 2002:a5d:59c5:0:b0:3a6:ec41:b9df with SMTP id ffacd0b85a97d-3a6ed64c0b6mr2122565f8f.49.1750854327273; Wed, 25 Jun 2025 05:25:27 -0700 (PDT) Received: from ?IPV6:2003:d8:2f12:1b00:5d6b:db26:e2b7:12? (p200300d82f121b005d6bdb26e2b70012.dip0.t-ipconnect.de. [2003:d8:2f12:1b00:5d6b:db26:e2b7:12]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a6e80f294asm4571380f8f.58.2025.06.25.05.25.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 25 Jun 2025 05:25:26 -0700 (PDT) Message-ID: <9bb1e917-891d-4e1b-915f-98cdd5fc578b@redhat.com> Date: Wed, 25 Jun 2025 14:25:24 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 3/4] mm: Support batched unmap for lazyfree large folios during reclamation To: Lance Yang Cc: akpm@linux-foundation.org, baolin.wang@linux.alibaba.com, chrisl@kernel.org, kasong@tencent.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, lorenzo.stoakes@oracle.com, ryan.roberts@arm.com, v-songbaohua@oppo.com, x86@kernel.org, ying.huang@intel.com, zhengtangquan@oppo.com, Lance Yang , Barry Song <21cnbao@gmail.com> References: <2c19a6cf-0b42-477b-a672-ed8c1edd4267@redhat.com> <20250624162503.78957-1-ioworker0@gmail.com> <27d174e0-c209-4851-825a-0baeb56df86f@redhat.com> <938c4726-b93e-46df-bceb-65c7574714a6@linux.dev> <5ba95609-302b-456a-a863-2bd5df51baf2@redhat.com> <6179dd30-5351-4a79-b0d6-f0e85650a926@redhat.com> <5db6fb4c-079d-4237-80b3-637565457f39@redhat.com> <42f1d84f-2d17-43b7-8fa2-83322fcca44f@linux.dev> 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: <42f1d84f-2d17-43b7-8fa2-83322fcca44f@linux.dev> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: qvm6l9kcrmYzoA0r2EwcWbjyEDT20ikfYKwJaFMBCaA_1750854328 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250625_052531_292778_9805CA61 X-CRM114-Status: GOOD ( 16.67 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 25.06.25 14:20, Lance Yang wrote: > > > On 2025/6/25 20:09, David Hildenbrand wrote: >>> >>> Somehow, I feel we could combine your cleanup code—which handles a batch >>> size of "nr" between 1 and nr_pages—with the >>> "if (nr_pages == folio_nr_pages(folio)) goto walk_done" check. >> >> Yeah, that's what I was suggesting. It would have to be part of the >> cleanup I think. >> >> I'm still wondering if there is a case where >> >> if (nr_pages == folio_nr_pages(folio)) >>     goto walk_done; >> >> would be wrong when dealing with small folios. >> >>> In practice, this would let us skip almost all unnecessary checks, >>> except for a few rare corner cases. >>> >>> For those corner cases where "nr" truly falls between 1 and nr_pages, >>> we can just leave them as-is—performing the redundant check inside >>> page_vma_mapped_walk(). >> >> I mean, batching mapcount+refcount updates etc. is always a win. If we >> end up doing some unnecessary pte_none() checks, that might be >> suboptimal but mostly noise in contrast to the other stuff we will >> optimize out 🙂 >> >> Agreed that if we can easily avoid these pte_none() checks, we should do >> that. Optimizing that for "nr_pages == folio_nr_pages(folio)" makes sense. > > Hmm... I have a question about the reference counting here ... > > if (vma->vm_flags & VM_LOCKED) > mlock_drain_local(); > folio_put(folio); > /* We have already batched the entire folio */ > > Does anyone else still hold a reference to this folio after folio_put()? The caller of the unmap operation should better hold a reference :) Also, I am not sure why we don't perform a folio_put_refs(folio, nr_pages); ... :) -- Cheers, David / dhildenb