From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3C4C72ED144 for ; Mon, 20 Oct 2025 09:13:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760951622; cv=none; b=G5MRMvF+R8/8ILAXSS+2VyO8/Aet/NPz/jOozTRCGMGCF9HqhQDfK+e24IHFiyjRttWYGjgd31oePBx+wGEHtRs+t/Ajs2O0XFxxtCRgmHRP8NDOKhcJG62qx+E5FHi5yLzf4MyMhLSJim+sx0ns3WZ5d9oU5im9jOenXgr/G0U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760951622; c=relaxed/simple; bh=aUcQn5I0PiueTLpOZyiXPCO+z8+eH9JgH5aQUMhgFn8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Jpt4mrli7tUChYluvLBmWf86djtElNl80BMRsZBulQWEdO/rsnDvWkgDf8jfXNw2aI+pbVSkfFHZCq+GOYOAg3essdvdaVGj2uHBnaAl0wu3QEhBrP6zYlrIKi2b3MePZsPGcLIPd0v8TX2NgYdpn/4t186YoTQ8yEQcUHSdgVc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=H2mBd8BG; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="H2mBd8BG" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1760951620; 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=Eh0wHwo2LU2FIRX9AhMX9fHbYdP7OvIPgfEQ71tVBzI=; b=H2mBd8BGI+0Bh+38SCmJ1+oXxzxITNcbL+jg8R3MX0B31keBQU0aVoleJhusWmhb4tCVlI Ij55qm7ZKncDLcMh9uMcPXglLsbYT2X9sXDyB2wq00nr1GQxUiGnxUkIP1ifK/fHMj1gI9 KTlRBm0k8GniLgLKuTijlmHNoP4YZLE= 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-178-dBb3GYbqPMe5EVg3d3Sw9w-1; Mon, 20 Oct 2025 05:13:38 -0400 X-MC-Unique: dBb3GYbqPMe5EVg3d3Sw9w-1 X-Mimecast-MFC-AGG-ID: dBb3GYbqPMe5EVg3d3Sw9w_1760951617 Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-46e4cb3e4deso14512595e9.1 for ; Mon, 20 Oct 2025 02:13:38 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1760951617; x=1761556417; h=content-transfer-encoding:in-reply-to: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=Eh0wHwo2LU2FIRX9AhMX9fHbYdP7OvIPgfEQ71tVBzI=; b=PbtdCahkqfSDWmT3Ukxlu4HaBpPMyOYb8ROAmfGOawmJ5BK0iYKk6mGTOiHBPAdDgf K9Pwj4rzmdSpczZ4Mmb6ycWn7S4CS2ssQ6JGyineE52WCU7l2EDJas8nTkhp0vq0YjSW ImVe3jTbcT+1PYZz78Uony3oAPRwEZAkXHIO2P2dliN/xbmovfQf/50WqmlW9EskCnNR 4t7gcOzYVWNONkIpBSGjWOnvNfAS1XvVuxN7Bd3fcF8iNSbkZTAPtoom8R1lV2cQ/I01 K0wSEb7YeKke0Hp+EM5NzPGB63FzjLNmEc0PHGBfLDnevbbc8R59T5FtnQG9zCRBO8z2 btBQ== X-Forwarded-Encrypted: i=1; AJvYcCUnk3rS9lN9D1MtVfTqqzd87/5R/VnW9Ks9YdYcF3EZgswA8vME19BZm98eNISMq3PbDjIMhWMg7OpJZTo=@vger.kernel.org X-Gm-Message-State: AOJu0Yxc1nAG8efUjMgjZp0H+ysUUg1+2qaJPArapAjYWJs89vC7l6BN Z2RlKvHcIikbqdK9gkIptWD4Xw6S4PMm09PL5UA/CtKXTXScBHUtZPcQDT7JubEDZ3L58C/zy/y AjTq5xlKPZVLDf7pBlYj2AVr0whTg6Qr3KdkFBOKlxzUJXUJUL+cGHBMOkU/O+W/zQg== X-Gm-Gg: ASbGncvJ25xwIq2G419n3R+uyIdX/OxnOwYQ2lsqFgISqzBkBbcZXaqjY1jG5y4BHH3 +m6GZSgsVbt26I8sNbS+7IkKs3Mwca8Rx9RMweUL49H33bGW/UXhct91UAJGpSyNonGazxmq6vx ZJF0cbywlQCp5paEfK0+YICFjuhXOlSY883ADMRcOQpbYAzaeLw8/1dOMWGxpBxbWUDDaqkXeiA d1f67SSQETlIn9K5n4s2cVQrz2MuE5plRJlK+Rt8AlHgHgl7yetHAp9Q742OzrpeJiuHZRPvBWG P4Q0tBLnQUdDgfzPp/oljocfSsOzG+3OcEhSqiiqfjE/flYl9zZTxry/5j3GWdWIfu95vanckrZ oS45G9PncSv/O+0xZoh7xaShfGN1i8+DI9SRGAvkPbtfzDrNaVqGfSKvc9rwHNJqtq3mf7C5EML WUfV3501OkKv3kli2rY/4FdhalErw= X-Received: by 2002:a05:600c:3b98:b0:46e:6339:79c5 with SMTP id 5b1f17b1804b1-4711724b354mr119191845e9.5.1760951617111; Mon, 20 Oct 2025 02:13:37 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEFME1ceOxJyPsxu5kjPbUdJ41bH4P8jCHFCQX4VPWwz7nZ35nqwnC6x0CCerHmtu/XFIG6fA== X-Received: by 2002:a05:600c:3b98:b0:46e:6339:79c5 with SMTP id 5b1f17b1804b1-4711724b354mr119191525e9.5.1760951616638; Mon, 20 Oct 2025 02:13:36 -0700 (PDT) Received: from ?IPV6:2003:d8:2f0c:c200:fa4a:c4ff:1b32:21ce? (p200300d82f0cc200fa4ac4ff1b3221ce.dip0.t-ipconnect.de. [2003:d8:2f0c:c200:fa4a:c4ff:1b32:21ce]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-427ea5b3c56sm14482749f8f.18.2025.10.20.02.13.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 20 Oct 2025 02:13:36 -0700 (PDT) Message-ID: Date: Mon, 20 Oct 2025 11:13:34 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/3] mm: treewide: make get_free_pages() and return void * To: Jiri Slaby , Matthew Wilcox , Mike Rapoport Cc: Andrew Morton , Brendan Jackman , Greg Kroah-Hartman , Johannes Weiner , Julia Lawall , "Liam R. Howlett" , Lorenzo Stoakes , Michal Hocko , Suren Baghdasaryan , Vlastimil Babka , Zi Yan , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20251018093002.3660549-1-rppt@kernel.org> <3e798b9e-4915-404f-9197-ed3c32587141@kernel.org> <85707316-3f2b-4e29-b821-a32f9097244e@kernel.org> <635405e4-9423-4a25-a6e7-e03c8ea0bcbe@redhat.com> <3b97b754-890a-46c6-b892-a0324d529a3d@kernel.org> From: David Hildenbrand Content-Language: en-US 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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <3b97b754-890a-46c6-b892-a0324d529a3d@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 20.10.25 11:08, Jiri Slaby wrote: > On 20. 10. 25, 11:02, David Hildenbrand wrote: >> Regarding the metadata overhead, in 2015 Linus wrote in that thread: >> >> "Long ago, allocating a page using kmalloc() was a bad idea, because >> there was overhead for it in the allocation and the code. >> >> These days, kmalloc() not only doesn't have the allocation overhead, >> but may actually scale better too, thanks to percpu caches etc." >> >> What's that status of that 10 years later? > > AFAI skimmed through the code, for allocations > 2 pages > (KMALLOC_MAX_CACHE_SIZE) -- if size is a constant -- slub resorts to > alloc_pages(). > > For smaller ones (1 and 2 pages), there is a very little overhead in > struct slab -- mm people, please correct me if I am wrong. If it's really only "struct slab", then there is currently no overhead. Once it is decoupled from "struct page", there would be some. IIUC, I'm surprised that larger allocations wouldn't currently end up in PageSlab() pages. -- Cheers David / dhildenb