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 837241A9FA4; Fri, 20 Mar 2026 08:39:56 +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=1773995996; cv=none; b=dnuY8ov81wnA4zQn+I8Jrh+EDYjk4hgF9nrEjWBIhVzpd7S0g4LYzHShEmeiPpKpopr7TMIj6aVkffR9DaKc7eilQHBGe6FsieHbW8Y1QYyJSnXzm3xAF4mu0xmAEiNwT0Arq+C+tD+RnZpok/5MtEDSXyCXdyWBDW3Vw39+Wgk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773995996; c=relaxed/simple; bh=dpiUkOjr5sqNyRGJepwowr5KdgHmx35gBDJu9PI+O2g=; h=Message-ID:Date:MIME-Version:Subject:To:References:From: In-Reply-To:Content-Type; b=iTiTet1+R4zPTQs3sJXBAXWOuUNKjy4OE8vQCnUPZmCRZZbPFUijSTRUoSPcSmVXtL4beFEI4II5UbvALzHBY2YTVlB4vkEcHb2P/Ktons9mpkbtZ49/I3Z5ygEseI00IYKC5NoIeTYFJdvhl3bCP4nIj/wYCItJ5QyGQTMLKQs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=FJxTn6zS; 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="FJxTn6zS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6403AC4CEF7; Fri, 20 Mar 2026 08:39:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773995996; bh=dpiUkOjr5sqNyRGJepwowr5KdgHmx35gBDJu9PI+O2g=; h=Date:Subject:To:References:From:In-Reply-To:From; b=FJxTn6zS+2yrWebrDGULdt/62qRH+rE+1KG2DUj7cSrU08NxwcTXH1Yl8nSO55zV6 f/wSGxgapmNbAOjstoE4hJ4ptnO7PGfPTXkxFmfmq7g2CvPB92DJLuVUHBn5kF7Q4t z8a1iXLZv0BwTaell+wgvVZeJ1IJTYeC3feBB6zkAWlaOZeogxNagI+Kf1daSeKLzn K6gbFrEF6VSz6sWYfsHmSjJy6TX0Epi0mixvq0gw8QZQomnVLCLNjMw5vEEUa8KAYB fgNg3xZ/x/ENpLz0Uv9oRlIJ1+kmYc86b0DobP/nXzdmuJOHI/DFUM5vdet3oQ5vw6 JlgLwPP6PsBzw== Message-ID: Date: Fri, 20 Mar 2026 09:39:49 +0100 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 v2 2/3] vmalloc: Optimize vfree To: Vlastimil Babka , 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 (Oracle)" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, Ryan.Roberts@arm.com, david.hildenbrand@arm.com References: <20260316113209.945853-1-usama.anjum@arm.com> <20260316113209.945853-3-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 On 3/16/26 16:49, Vlastimil Babka wrote: > On 3/16/26 12:31, 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 v1: >> - Rebase on mm-new >> - Rerun benchmarks >> --- >> mm/vmalloc.c | 34 +++++++++++++++++++++++++--------- >> 1 file changed, 25 insertions(+), 9 deletions(-) >> >> diff --git a/mm/vmalloc.c b/mm/vmalloc.c >> index c607307c657a6..8b935395fb068 100644 >> --- a/mm/vmalloc.c >> +++ b/mm/vmalloc.c >> @@ -3459,18 +3459,34 @@ void vfree(const void *addr) >> >> if (unlikely(vm->flags & VM_FLUSH_RESET_PERMS)) >> vm_reset_perms(vm); >> - for (i = 0; i < vm->nr_pages; i++) { >> - struct page *page = vm->pages[i]; >> + >> + if (vm->nr_pages) { >> + bool account = !(vm->flags & VM_MAP_PUT_PAGES); >> + unsigned long start_pfn, pfn; >> + struct page *page = vm->pages[0]; >> + int nr = 1; >> >> BUG_ON(!page); >> - /* >> - * High-order allocs for huge vmallocs are split, so >> - * can be freed as an array of order-0 allocations >> - */ >> - if (!(vm->flags & VM_MAP_PUT_PAGES)) >> + start_pfn = page_to_pfn(page); >> + if (account) >> mod_lruvec_page_state(page, NR_VMALLOC, -1); >> - __free_page(page); >> - cond_resched(); >> + >> + for (i = 1; i < vm->nr_pages; i++) { >> + page = vm->pages[i]; >> + BUG_ON(!page); > > We shouldn't be adding BUG_ON()'s. Rather demote also the pre-existing one > to VM_WARN_ON_ONCE() and skip gracefully. > >> + if (account) >> + mod_lruvec_page_state(page, NR_VMALLOC, -1); > > I think we should be able to batch this too to use "nr"? Are we sure that pages cannot cross nodes etc? It could happen that we have a contig range that spans zones/nodes/etc ... Anyhow, should we try to decouple both things, providing a core-mm function to do the page freeing? We do have something similar, optimized unpinning of large folios, in unpin_user_pages_dirty_lock(). This here is a bit different. So what I am thinking about for this code here to do: if (!(vm->flags & VM_MAP_PUT_PAGES)) { for (i = 0; i < vm->nr_pages; i++) mod_lruvec_page_state(vm->pages[i], NR_VMALLOC, -1); } free_pages_bulk(vm->pages, vm->nr_pages); We could optimize the first loop to do batching where possible as well. free_pages_bulk() would match alloc_pages_bulk() void free_pages_bulk(struct page **page_array, unsigned long nr_pages) Internally we'd do the contig handling. Was that already discussed? -- Cheers, David