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 99C334014AD; Wed, 25 Mar 2026 15:01:10 +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=1774450870; cv=none; b=CUvu8gPIZ8qcHMzwxrC0x7vJG3L95PoxzIPznsaKvhBHdiKwt3Q1HRevOxZ6kReslWUSXBf1Ysjd9hDevZvrLPD3WbdKUstUshWX9lq5bnUFO0limuSybxnsSB4EO85Yw6CAsynbafv2U1I1y5e1YzXj4KN5z8ANBVR7SJwaK8o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774450870; c=relaxed/simple; bh=qVRF9sk1Jd0nZq4F7HqfXkke05aS+QAgoJZ+38yMEVo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=RkmI3oPgR8wE36Rh7xB1C9vJ7aTCi0CiCneZ/Od/R47MHGCeO4xciTsyYsGaHWFq61uvySRmK5KrWREJWYTK/LBISbpmyECOKAtyzrzuXkhd/9qwkAGQ3QknzxuTU1hqAK8FFC2ZIQidf02EJ/qWn0pYWj90aMO3wrz9e0W87xo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fQ6c99w/; 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="fQ6c99w/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E057FC4CEF7; Wed, 25 Mar 2026 15:01:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774450870; bh=qVRF9sk1Jd0nZq4F7HqfXkke05aS+QAgoJZ+38yMEVo=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=fQ6c99w/XgLo2BKV8yRY1ozwD37yWcqUOQeYTXfAO3ZrgPhLDkzCzD/8FjPm1qlnW AoLx3T/NedKCCagIUrPPaTBC4SRlgZ6ZU1+Htd2WmqYjZs9EjUXgG35+GTMH6nMBfN nA8T0mS0f63WCHEfF9f2oll36MM2qlAlsKFmVvxEUdR6dbIhOk4naAtOTMSWtxrYsI ltRG9yvLfwZTG2/HQW03+fN/Y6j+JT8ZEWVMqtDI+2/Do1xgkfGR4pxkBQtigDMlaY KPAIbLo7IegjxHY/7oRPryoQPlhvkF0j57qUGQ9KCjMHtX9bXVonEGx8YwK5P/HdXa 6zRk8g5utnl0A== Message-ID: <0030565c-ec0d-47f6-94a9-b16e76800875@kernel.org> Date: Wed, 25 Mar 2026 16:01:02 +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 2/3] vmalloc: Optimize vfree To: Muhammad Usama Anjum Cc: Andrew Morton , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , 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: <20260324133538.497616-1-usama.anjum@arm.com> <20260324133538.497616-3-usama.anjum@arm.com> <80dc24d6-944c-46d8-a692-24a9be408a59@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: <80dc24d6-944c-46d8-a692-24a9be408a59@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/25/26 15:26, Muhammad Usama Anjum wrote: > On 25/03/2026 10:05 am, David Hildenbrand (Arm) wrote: >> On 3/24/26 14:35, Muhammad Usama Anjum wrote: >>> From: Ryan Roberts >>> >>> Whenever vmalloc allocates high order pages (e.g. for a huge mapping) it >>> must immediately split_page() to order-0 so that it remains compatible >>> with users that want to access the underlying struct page. >>> Commit a06157804399 ("mm/vmalloc: request large order pages from buddy >>> allocator") recently made it much more likely for vmalloc to allocate >>> high order pages which are subsequently split to order-0. >>> >>> Unfortunately this had the side effect of causing performance >>> regressions for tight vmalloc/vfree loops (e.g. test_vmalloc.ko >>> benchmarks). See Closes: tag. This happens because the high order pages >>> must be gotten from the buddy but then because they are split to >>> order-0, when they are freed they are freed to the order-0 pcp. >>> Previously allocation was for order-0 pages so they were recycled from >>> the pcp. >>> >>> It would be preferable if when vmalloc allocates an (e.g.) order-3 page >>> that it also frees that order-3 page to the order-3 pcp, then the >>> regression could be removed. >>> >>> So let's do exactly that; use the new __free_contig_range() API to >>> batch-free contiguous ranges of pfns. This not only removes the >>> regression, but significantly improves performance of vfree beyond the >>> baseline. >>> >>> A selection of test_vmalloc benchmarks running on arm64 server class >>> system. mm-new is the baseline. Commit a06157804399 ("mm/vmalloc: request >>> large order pages from buddy allocator") was added in v6.19-rc1 where we >>> see regressions. Then with this change performance is much better. (>0 >>> is faster, <0 is slower, (R)/(I) = statistically significant >>> Regression/Improvement): >>> >>> +-----------------+----------------------------------------------------------+-------------------+--------------------+ >>> | Benchmark | Result Class | mm-new | this series | >>> +=================+==========================================================+===================+====================+ >>> | micromm/vmalloc | fix_align_alloc_test: p:1, h:0, l:500000 (usec) | 1331843.33 | (I) 67.17% | >>> | | fix_size_alloc_test: p:1, h:0, l:500000 (usec) | 415907.33 | -5.14% | >>> | | fix_size_alloc_test: p:4, h:0, l:500000 (usec) | 755448.00 | (I) 53.55% | >>> | | fix_size_alloc_test: p:16, h:0, l:500000 (usec) | 1591331.33 | (I) 57.26% | >>> | | fix_size_alloc_test: p:16, h:1, l:500000 (usec) | 1594345.67 | (I) 68.46% | >>> | | fix_size_alloc_test: p:64, h:0, l:100000 (usec) | 1071826.00 | (I) 79.27% | >>> | | fix_size_alloc_test: p:64, h:1, l:100000 (usec) | 1018385.00 | (I) 84.17% | >>> | | fix_size_alloc_test: p:256, h:0, l:100000 (usec) | 3970899.67 | (I) 77.01% | >>> | | fix_size_alloc_test: p:256, h:1, l:100000 (usec) | 3821788.67 | (I) 89.44% | >>> | | fix_size_alloc_test: p:512, h:0, l:100000 (usec) | 7795968.00 | (I) 82.67% | >>> | | fix_size_alloc_test: p:512, h:1, l:100000 (usec) | 6530169.67 | (I) 118.09% | >>> | | full_fit_alloc_test: p:1, h:0, l:500000 (usec) | 626808.33 | -0.98% | >>> | | kvfree_rcu_1_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 532145.67 | -1.68% | >>> | | kvfree_rcu_2_arg_vmalloc_test: p:1, h:0, l:500000 (usec) | 537032.67 | -0.96% | >>> | | long_busy_list_alloc_test: p:1, h:0, l:500000 (usec) | 8805069.00 | (I) 74.58% | >>> | | pcpu_alloc_test: p:1, h:0, l:500000 (usec) | 500824.67 | 4.35% | >>> | | random_size_align_alloc_test: p:1, h:0, l:500000 (usec) | 1637554.67 | (I) 76.99% | >>> | | random_size_alloc_test: p:1, h:0, l:500000 (usec) | 4556288.67 | (I) 72.23% | >>> | | vm_map_ram_test: p:1, h:0, l:500000 (usec) | 107371.00 | -0.70% | >>> +-----------------+----------------------------------------------------------+-------------------+--------------------+ >>> >>> Fixes: a06157804399 ("mm/vmalloc: request large order pages from buddy allocator") >>> Closes: https://lore.kernel.org/all/66919a28-bc81-49c9-b68f-dd7c73395a0d@arm.com/ >>> Signed-off-by: Ryan Roberts >>> Co-developed-by: Muhammad Usama Anjum >>> Signed-off-by: Muhammad Usama Anjum >>> --- >>> Changes since v2: >>> - Remove BUG_ON in favour of simple implementation as this has never >>> been seen to output any bug in the past as well >>> - Move the free loop to separate function, free_pages_bulk() >>> - Update stats, lruvec_stat in separate loop >>> >>> Changes since v1: >>> - Rebase on mm-new >>> - Rerun benchmarks >>> >>> Made-with: Cursor >>> --- >>> include/linux/gfp.h | 2 ++ >>> mm/page_alloc.c | 23 +++++++++++++++++++++++ >>> mm/vmalloc.c | 16 +++++----------- >>> 3 files changed, 30 insertions(+), 11 deletions(-) >>> >>> diff --git a/include/linux/gfp.h b/include/linux/gfp.h >>> index 7c1f9da7c8e56..71f9097ab99a0 100644 >>> --- a/include/linux/gfp.h >>> +++ b/include/linux/gfp.h >>> @@ -239,6 +239,8 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid, >>> struct page **page_array); >>> #define __alloc_pages_bulk(...) alloc_hooks(alloc_pages_bulk_noprof(__VA_ARGS__)) >>> >>> +void free_pages_bulk(struct page **page_array, unsigned long nr_pages); >>> + >>> unsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp, >>> unsigned long nr_pages, >>> struct page **page_array); >>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>> index eedce9a30eb7e..250cc07e547b8 100644 >>> --- a/mm/page_alloc.c >>> +++ b/mm/page_alloc.c >>> @@ -5175,6 +5175,29 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid, >>> } >>> EXPORT_SYMBOL_GPL(alloc_pages_bulk_noprof); >>> >> >> Can we add some kerneldoc describing call context etc? > Yes, I'll add short kerneldoc here. >> >>> +void free_pages_bulk(struct page **page_array, unsigned long nr_pages) >>> +{ >>> + unsigned long start_pfn = 0, pfn; >>> + unsigned long i, nr_contig = 0; >>> + >>> + for (i = 0; i < nr_pages; i++) { >>> + pfn = page_to_pfn(page_array[i]); >>> + if (!nr_contig) { >>> + start_pfn = pfn; >>> + nr_contig = 1; >>> + } else if (start_pfn + nr_contig != pfn) { >>> + __free_contig_range(start_pfn, nr_contig); >>> + start_pfn = pfn; >>> + nr_contig = 1; >>> + cond_resched(); >>> + } else { >>> + nr_contig++; >>> + } >>> + } >> >> Could we use num_pages_contiguous() here? >> >> while (nr_pages) { >> unsigned long nr_contig_pages = num_pages_contiguous(page_array, nr_pages); >> >> __free_contig_range(pfn_to_page(*page_array), nr_contig_pages); >> >> nr_pages -= nr_contig; >> page_array += nr_contig; >> cond_resched(); >> } >> >> Something like that? > __free_contig_range() is already checking for the sections. If > num_pages_contiguous() is called here, it'll cause the duplication > of the section check. No problem. For configs we care about it's optimized out entirely either way. -- Cheers, David