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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (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 F40A3C47258 for ; Wed, 31 Jan 2024 11:13:57 +0000 (UTC) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=bLX8t9qM; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=VSs7TDgG; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4TPztr4lhXz3cTr for ; Wed, 31 Jan 2024 22:13:56 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=bLX8t9qM; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=VSs7TDgG; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=redhat.com (client-ip=170.10.129.124; helo=us-smtp-delivery-124.mimecast.com; envelope-from=david@redhat.com; receiver=lists.ozlabs.org) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4TPzt12fZCz30gC for ; Wed, 31 Jan 2024 22:13:12 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1706699589; 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=d4ma9zbE8mjb8i+FauSpNHy+FN/rZ5fB2oL3RLjV6rs=; b=bLX8t9qM4WUR8REWg+0XkfWUSQK09h+hi9UWdax3f5UNM9Qc1Tj8CrjzSs/VkA/AKyJYL2 IDZOuaEl1tczJltgyUs5jAa+ciqy9UIb/YYCBCwPsN9nBIPPyjrljmhGGpKr6C4SOycd/D IrOS1PCi+JUkz41Y0r8mDvT9ynhc9pI= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1706699590; 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=d4ma9zbE8mjb8i+FauSpNHy+FN/rZ5fB2oL3RLjV6rs=; b=VSs7TDgGaUSr2Xh7gshkdiY3N9eXYVn9USZSt69osZbF5iYcZ+oBddH9Rqwxh1fxgCsRpZ 0vo7eDfQRp5LYtjLLYvmcDFWSznmZHb1mlXOmRM88ZZQz7JNhdYKE1LHK/Ax0hf/p0FXRm WrrvqyZBXL/yIhf7N0Wgxp4nBDFkmPs= 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-231-0IbfNVSaMFeZFqqPC8ajcQ-1; Wed, 31 Jan 2024 06:13:08 -0500 X-MC-Unique: 0IbfNVSaMFeZFqqPC8ajcQ-1 Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-40fb03d8a39so5567715e9.3 for ; Wed, 31 Jan 2024 03:13:07 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1706699587; x=1707304387; 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=d4ma9zbE8mjb8i+FauSpNHy+FN/rZ5fB2oL3RLjV6rs=; b=oKfpYk8xYRESLpoTCf8OdTGhnC2rC4zQVSk/AvbKLKwTiWp1+c2eL2hoQtaMPxJGd3 ikmUJbKjrk/4cRurzbEcTd7iyiawvHYgK7V4CewTRwlL3sqtmgwCD5dIwzvNggv7Guzy IaH+n8LT8cQtSwZ+zxfpW3IBQph7+IEx5XOwZ0ktvd5nig2rvsIH9ylB+lqH4wVKhc5x OsM3tUZYszpq/RjtZ4B67VwycZf78/nvZ0Yg9ZQqXMHD5PamIzmXoKK63hrFIdR0wXCT F4IaN7ES7uBU6tk/kLio1Xsi3osGyD8GEdoAUtg+XCAFYOXtfh+SGKbKv+06nzTym/7N 3Zmw== X-Gm-Message-State: AOJu0YxKsiCAMVMJx4T1n7W7I0x1Jh5Rjh5ix7iqGnvz63ssML1HUuZm qKY8WL//yHLoauoQWe+WYFy33q+NenY3uIOU7sb/Nk72NJQnIobBEFgcT0Q5sJUSAASuOOrSMWQ tjvjfgwmVwIIzh17+V1ELrlZPkFaZFXfVpk84IbuTm4caeRmGqbBmp2PP7xTm4sw= X-Received: by 2002:a05:600c:470d:b0:40e:f656:39f with SMTP id v13-20020a05600c470d00b0040ef656039fmr1018343wmo.6.1706699586979; Wed, 31 Jan 2024 03:13:06 -0800 (PST) X-Google-Smtp-Source: AGHT+IFqBwS6p6bJR9z+v39DGZKJ94gGFj7YXuQe4rd8sPOmEQeUSMAmCXotFvLHcNalUBQDlimQJQ== X-Received: by 2002:a05:600c:470d:b0:40e:f656:39f with SMTP id v13-20020a05600c470d00b0040ef656039fmr1018321wmo.6.1706699586591; Wed, 31 Jan 2024 03:13:06 -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 cl3-20020a5d5f03000000b0033afd49cac7sm3390196wrb.43.2024.01.31.03.13.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 31 Jan 2024 03:13:06 -0800 (PST) Message-ID: Date: Wed, 31 Jan 2024 12:13:05 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 9/9] mm/memory: optimize unmap/zap with PTE-mapped THP To: Ryan Roberts , linux-kernel@vger.kernel.org References: <20240129143221.263763-1-david@redhat.com> <20240129143221.263763-10-david@redhat.com> <424115a2-a924-4c28-8027-32db6ab9278d@arm.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: <424115a2-a924-4c28-8027-32db6ab9278d@arm.com> 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-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, Alexander Gordeev , Christian Borntraeger , Arnd Bergmann , Vasily Gorbik , Peter Zijlstra , "Aneesh Kumar K.V" , linuxppc-dev@lists.ozlabs.org, Matthew Wilcox , linux-mm@kvack.org, Nick Piggin , Catalin Marinas , "Naveen N. Rao" , Andrew Morton , Will Deacon , Heiko Carstens , Sven Schnelle Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" >>>> -        folio_remove_rmap_pte(folio, page, vma); >>>> +        folio_remove_rmap_ptes(folio, page, nr, vma); >>>> + >>>> +        /* Only sanity-check the first page in a batch. */ >>>>           if (unlikely(page_mapcount(page) < 0)) >>>>               print_bad_pte(vma, addr, ptent, page); >>> >>> Is there a case for either removing this all together or moving it into >>> folio_remove_rmap_ptes()? It seems odd to only check some pages. >>> >> >> I really wanted to avoid another nasty loop here. >> >> In my thinking, for 4k folios, or when zapping subpages of large folios, we >> still perform the exact same checks. Only when batching we don't. So if there is >> some problem, there are ways to get it triggered. And these problems are barely >> ever seen. >> >> folio_remove_rmap_ptes() feels like the better place -- especially because the >> delayed-rmap handling is effectively unchecked. But in there, we cannot >> "print_bad_pte()". >> >> [background: if we had a total mapcount -- iow cheap folio_mapcount(), I'd check >> here that the total mapcount does not underflow, instead of checking per-subpage] > > All good points... perhaps extend the comment to describe how this could be > solved in future with cheap total_mapcount()? Or in the commit log if you prefer? I'll add more meat to the cover letter, thanks! -- Cheers, David / dhildenb