From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 06F3F36AB50; Wed, 1 Apr 2026 09:59:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775037572; cv=none; b=akbeeUYdWSR8BKHXh0Ms1OR5BnMOybxKSCpL3YkgkGRK9rSu//QgtdfOM5u6cGDk9MTj//dTyZJ4ABnfE74kN5+aYmaLZcqlYOtuOGdiOBliwfadoTQMrGetgw3s8GpbMfFKLB59nutEiJRg7tOpct1AZUMZT2TjcJ1ntj7n/y8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775037572; c=relaxed/simple; bh=sE2NJz5Ms6JXDjZrrUZlQ/gxohVll2s38Xf85dSR7bE=; h=Message-ID:Date:MIME-Version:Subject:To:References:From: In-Reply-To:Content-Type; b=OI37Lx9SCC3vqwb0u3EIYLTlaH84s5Oz+0rYfzMKBFzmAio0YTZjlwvvtyNnPZ8ZdSznFDg1Vkk78OD999hw/VdSESHm2dR/gwph0Cu6nnPKfNtrfxsiu/21lq/CUw+Et7pAg6MdkQF734+Kwjxi6D9oYUJVHJJzRIIPwb+Hjm8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ZvURe5r5; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ZvURe5r5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C3783C2BCB0; Wed, 1 Apr 2026 09:59:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775037571; bh=sE2NJz5Ms6JXDjZrrUZlQ/gxohVll2s38Xf85dSR7bE=; h=Date:Subject:To:References:From:In-Reply-To:From; b=ZvURe5r5yOCo9ztBIJBW4TMfK36VYFZwKZWDyc9KrUmbIP005k2bj5lm3V5tydioi yOoTyM8nsjW+Lu6kWlK2ZGWtUMu1D6iSTTTvBXyfh6i5Q/fACnVaOoXtHf2NaCCAT/ o73G8A5NZQ1Haj2dDByhKlzu0VX3vlNCbS8PSo5r3J22kqM8udbxcK/+FosU390bsv +f+90yIcWXKOdmYIyUoHcc9Zn37TsfC63QkTA9ZKomKIzzMd1GrOJmqP+vyUQtADYE JMmr1eADUcc5cLC9MFmmQfOM3aF2HFizpgysDH8rl/N9oNGFU+IjPHxlnOZQ7HKpNY B4z1WzBjjHJhQ== Message-ID: <6494c9d9-9598-437a-bc50-54a4b6401a3d@kernel.org> Date: Wed, 1 Apr 2026 11:59:24 +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 v5 1/3] mm/page_alloc: Optimize free_contig_range() To: "Vlastimil Babka (SUSE)" , Muhammad Usama Anjum , Andrew Morton , Lorenzo Stoakes , "Liam R . Howlett" , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Uladzislau Rezki , Nick Terrell , David Sterba , Vishal Moola , linux-mm@kvack.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, Ryan.Roberts@arm.com, david.hildenbrand@arm.com References: <20260331152208.975266-1-usama.anjum@arm.com> <20260331152208.975266-2-usama.anjum@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit >> +static void free_prepared_contig_range(struct page *page, >> + unsigned long nr_pages) >> +{ >> + while (nr_pages) { >> + unsigned long pfn = page_to_pfn(page); > > Sorry for not noticing earlier. I now realized that because here we are > guaranteed to be restricted to the same section, we can do page_to_pfn() > just once outside the loop and then "pfn += 1UL << order;" below? +1 > >> + unsigned int order; >> + >> + /* We are limited by the largest buddy order. */ >> + order = pfn ? __ffs(pfn) : MAX_PAGE_ORDER; >> + /* Don't exceed the number of pages to free. */ >> + order = min_t(unsigned int, order, ilog2(nr_pages)); >> + order = min_t(unsigned int, order, MAX_PAGE_ORDER); >> + >> + /* >> + * Free the chunk as a single block. Our caller has already >> + * called free_pages_prepare() for each order-0 page. >> + */ >> + __free_frozen_pages(page, order, FPI_PREPARED); >> + >> + page += 1UL << order; >> + nr_pages -= 1UL << order; >> + } >> +} >> + >> +static void __free_contig_range_common(unsigned long pfn, unsigned long nr_pages, >> + bool is_frozen) >> +{ >> + struct page *page, *start = NULL; >> + unsigned long nr_start = 0; >> + unsigned long start_sec; >> + unsigned long i; >> + >> + for (i = 0; i < nr_pages; i++) { >> + bool can_free = true; >> + >> + /* >> + * Contiguous PFNs might not have contiguous "struct pages" >> + * in some kernel configs: page++ across a section boundary >> + * is undefined. Use pfn_to_page() for each PFN. >> + */ >> + page = pfn_to_page(pfn + i); > > Hm ideally we'd have some pfn+page iterator thingy that would just do a > page++ on configs where it's contiguous and this more expensive operation > otherwise. Wonder why we don't have it yet. But that's for a possible > followup, not required now. pfn_to_page() is on relevant configs close to just a "page + i". Not entirely, but I am not sure if the micro-gain would really be worth it. E.g., on CONFIG_SPARSEMEM_VMEMMAP #define __pfn_to_page(pfn) vmemmap + (pfn) Acked-by: David Hildenbrand (Arm) -- Cheers, David