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 811783A6EF9; Wed, 25 Mar 2026 10:15:08 +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=1774433708; cv=none; b=BnpwSVcmgO1sMZ2kY0eqJj+QmiNWYgozzhNu7PrKWNtoCyJ0O4+JOF72C6PNefwhJ2TskSa4PuKAqBm6IgyMw/NTUdgDNUH3iICar7dRX3TObMCUfWImxIQUsrzS94Qy+TADSqf7vCRsC0iZ5KN2l08PsY2u0OXozCzm5toVtDw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774433708; c=relaxed/simple; bh=I5ub2k82QnwWVmEhtM1D7FjRhq6hNb9lhP0IWUgTASI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=OFozyGFLx/IeAWUF1ymNaTFLGqqHPPGs51DoD6kzbCCSnRfM2idrvU4eZScfHXZBqAxOGH13pC/vslO5eRqHKu0OUWiFVA8QdXIJgtt/bDiACDI660pR29gVHWwbFjmdrD4ujpmVU7FtLGxM4a7pzZ/ddouytQ7sbTy4AXgl/UU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=IFxX7Nds; 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="IFxX7Nds" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AA8D7C2BCB0; Wed, 25 Mar 2026 10:15:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774433708; bh=I5ub2k82QnwWVmEhtM1D7FjRhq6hNb9lhP0IWUgTASI=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=IFxX7NdsgnjOpXghpl0RmVj4wVEDyI5Jy48RxLlNG88zw7OyDDuoUs8xa/q5Uy4wy vK7SHK9ZugFF4NGfi//A3YfW/Yy0W9QSW3k9/QPKIX1hxLW8F6T3EaXfL88sHUN1ZI nXQlqXOEKbdYxV/4KpMMTUkDczB7Ku3+EQd7c6JTMCEolGFXfraxDuqY9grfEIwOTg ro2czttNSHsm3rYuKx4wbPXj9b26JsQsj14dCBMm56I/qIisTC/RhZcb/QONxzLhPy 1cC5SGd/rP6dQmn2r/k6kotkS5pogKGZbH8M+bq6/sghIKh0TyE7rKAHuqcj15lYJe 76pMw9Yd0hoRA== Message-ID: <4ca68533-9abf-4d54-ba15-5ab9bc3ed0dc@kernel.org> Date: Wed, 25 Mar 2026 11:14:59 +0100 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 3/3] mm/page_alloc: Optimize __free_contig_frozen_range() To: Zi Yan , Muhammad Usama Anjum Cc: Andrew Morton , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , 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: <20260324133538.497616-1-usama.anjum@arm.com> <20260324133538.497616-4-usama.anjum@arm.com> <309C0716-A53B-422D-ABDE-E865DE0473BB@nvidia.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: <309C0716-A53B-422D-ABDE-E865DE0473BB@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/24/26 16:06, Zi Yan wrote: > On 24 Mar 2026, at 9:35, Muhammad Usama Anjum wrote: > >> Apply the same batch-freeing optimization from free_contig_range() to the >> frozen page path. The previous __free_contig_frozen_range() freed each >> order-0 page individually via free_frozen_pages(), which is slow for the >> same reason the old free_contig_range() was: each page goes to the >> order-0 pcp list rather than being coalesced into higher-order blocks. >> >> Rewrite __free_contig_frozen_range() to call free_pages_prepare() for >> each order-0 page, then batch the prepared pages into the largest >> possible power-of-2 aligned chunks via free_prepared_contig_range(). >> If free_pages_prepare() fails (e.g. HWPoison, bad page) the page is >> deliberately not freed; it should not be returned to the allocator. >> >> I've tested CMA through debugfs. The test allocates 16384 pages per >> allocation for several iterations. There is 3.5x improvement. >> >> Before: 1406 usec per iteration >> After: 402 usec per iteration >> >> Before: >> >> 70.89% 0.69% cma [kernel.kallsyms] [.] free_contig_frozen_range >> | >> |--70.20%--free_contig_frozen_range >> | | >> | |--46.41%--__free_frozen_pages >> | | | >> | | --36.18%--free_frozen_page_commit >> | | | >> | | --29.63%--_raw_spin_unlock_irqrestore >> | | >> | |--8.76%--_raw_spin_trylock >> | | >> | |--7.03%--__preempt_count_dec_and_test >> | | >> | |--4.57%--_raw_spin_unlock >> | | >> | |--1.96%--__get_pfnblock_flags_mask.isra.0 >> | | >> | --1.15%--free_frozen_page_commit >> | >> --0.69%--el0t_64_sync >> >> After: >> >> 23.57% 0.00% cma [kernel.kallsyms] [.] free_contig_frozen_range >> | >> ---free_contig_frozen_range >> | >> |--20.45%--__free_contig_frozen_range >> | | >> | |--17.77%--free_pages_prepare >> | | >> | --0.72%--free_prepared_contig_range >> | | >> | --0.55%--__free_frozen_pages >> | >> --3.12%--free_pages_prepare >> >> Suggested-by: Zi Yan >> Signed-off-by: Muhammad Usama Anjum >> --- >> Changes since v2: >> - Rework the loop to check for memory sections just like __free_contig_range() >> - Didn't add reviewed-by tags because of rework >> --- >> mm/page_alloc.c | 26 ++++++++++++++++++++++++-- >> 1 file changed, 24 insertions(+), 2 deletions(-) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index 250cc07e547b8..26eac35ef73bd 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -7038,8 +7038,30 @@ static int __alloc_contig_verify_gfp_mask(gfp_t gfp_mask, gfp_t *gfp_cc_mask) >> >> static void __free_contig_frozen_range(unsigned long pfn, unsigned long nr_pages) >> { >> - for (; nr_pages--; pfn++) >> - free_frozen_pages(pfn_to_page(pfn), 0); >> + struct page *page = pfn_to_page(pfn); >> + struct page *start = NULL; >> + unsigned long start_sec; >> + unsigned long i; >> + >> + for (i = 0; i < nr_pages; i++, page++) { >> + if (!free_pages_prepare(page, 0)) { >> + if (start) { >> + free_prepared_contig_range(start, page - start); >> + start = NULL; >> + } >> + } else if (start && >> + memdesc_section(page->flags) != start_sec) { >> + free_prepared_contig_range(start, page - start); >> + start = page; >> + start_sec = memdesc_section(page->flags); >> + } else if (!start) { >> + start = page; >> + start_sec = memdesc_section(page->flags); >> + } >> + } >> + >> + if (start) >> + free_prepared_contig_range(start, page - start); >> } > > This looks almost the same as __free_contig_range(). > > Two approaches to deduplicate the code: > > 1. __free_contig_range() first does put_page_testzero() > on all pages and call __free_contig_frozen_range() > on the range, __free_contig_frozen_range() will need > to skip not frozen pages. It is not ideal. Right, let's not do that. > > 2. add a helper function > __free_contig_range_common(unsigned long pfn, > unsigned long nr_pages, bool is_page_frozen), > and > a. call __free_contig_range_common(..., /*is_page_frozen=*/ false) > in __free_contig_range(), > b. __free_contig_range_common(..., /*is_page_frozen=*/ true) > in __free_contig_frozen_range(). > As long as it's an internal helper, that makes sense. I wouldn't want to expose the bool in the external interface. Thanks! -- Cheers, David