From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 A1C3E3644DE for ; Tue, 14 Jul 2026 10:56:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784026563; cv=none; b=UC1F117J5wiKhR1NRrGurfRw7S75Q2bBtv8r+aZGKwdJ6yiODfkFMf4pK6wWv90pFSObXT74CxKtY0OZcE77LCvm+WcjtMNa92fjHSoE+5YvjPb2Ctv6gXO+c2t+BKiiLCUgw1cQaOxGj7wp14cL5hgGW4q/bbp9jdFEE1bSOmI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784026563; c=relaxed/simple; bh=SyF21b+J1NAFd13smamnVk4xj7VKgn8cInhHYgzRE30=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=UW8ZiiMQlR8hVdcRogClbErJZA5TLLmF3IAVY+Zudbs1mc28lLWtsOaeYWEuk2UnScDLC2zZicWUaSwb/htqbkhPF1gdcnK6FGM6DCBSHFkzAomxJsdI9IdOf3XEOUdE2We67iY9I3PfeyLmvkA89GDa8u1RCKuD9xkKadWqoGk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=SVCboPYQ; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="SVCboPYQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 768711F000E9; Tue, 14 Jul 2026 10:55:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784026562; bh=h2a0KE3nESMqZxaA6l2dQ0EDA41Z0UjF+K+SGxf5zjk=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=SVCboPYQQhwjt1FcBVFT3LrF9qvX5MXkJ4mLsr6B1pkcUfrehPFqCnpbaqcBL9S8s Y1QwugCQbDWyy3mfuSsw341hDpBthdLtnpmYoQHZhoyTOPhfXoAWx6YVst6F829bq6 yXuH/lAwu8SLixrxKTg4Yv5IP4rZf3yQbCSHSEocYTRpHxzhkZ+Ri+piDKZD1Vl57h o+oNgLwUPEwhu9cPkc/J2LDhfnqNtQJxyGcr/7uf2nsxK0kZGGP5xzBMvnpzQ+XNSk iqNQZWngNAMA91T8PWref3qXOdIehXkxRUdI9yKMtSfFEGZ/4jqT7kEe/U5Ro+tEMb W+RPxECswLjjQ== Message-ID: Date: Tue, 14 Jul 2026 12:55:56 +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 0/6] mm: batch rmap walks during large folio migration To: Shivank Garg , Andrew Morton , Lorenzo Stoakes , Rik van Riel , "Liam R. Howlett" , Vlastimil Babka , Harry Yoo , Jann Horn , Lance Yang , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Zi Yan , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple Cc: Karim Manaouil , Frank van der Linden , Kinsey Ho , Wei Xu , Bharata B Rao , David Rientjes , Dev Jain , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260712-migrate-rmap-batch-v1-0-872a734431d1@amd.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: <20260712-migrate-rmap-batch-v1-0-872a734431d1@amd.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 7/12/26 09:38, Shivank Garg wrote: > Migrating a PTE-mapped large folio currently walks the folio's rmap > one page at a time. It does so twice per migration: > 1. try_to_migrate_one(): Replace present PTEs with migration entries > 2. remove_migration_pte(): Restore migration entries to working PTEs. > > For a folio with N contiguous PTEs, each walk repeats page_vma_mapped_walk() > and the associated operation per subpage of the folio. (256 iterations > for 1M folio). > > This series enables both walks to process a batch of consecutive PTEs > that map the same large folio and do some refactoring and clean up on > the way. > > Performance: > > AMD EPYC ZEN 3, 2-socket system (1 node per socket). > move_pages() migrating 1 GB from node 0 -> node 1, throughput > in GB/s: > batch- batch-restore + > folio vanilla restore unmap restore% restore+unmap% > 4K 2.98±0.09 2.95±0.07 3.06±0.05 -1.0% +2.6% > 64K 6.16±0.09 6.24±0.08 7.80±0.08 +1.3% +26.6% > 256K 6.85±0.06 6.85±0.09 9.54±0.19 +0.0% +39.3% > 1M 7.06±0.09 7.17±0.09 9.89±0.06 +1.5% +40.1% > 2M 10.97±0.17 10.67±0.13 10.69±0.15 -2.7% -2.6% > > In plain migration, the folio copy itself dominate the cost, so these rmap walk > savings are only partly visible end-to-end. > When the folio copy is batched-copy and offloaded to DMA engine [1], the copy is > no longer the bottlneck and rmap-walk batching translates into much larger gains: > > This series + [1], DMA Offload on PTDMA (DCBM), 16 channels: > > batch-copy > folio vanilla -offload(dcbm) dcbm+restore dcbm+restore+unmap > 4K 3.36 ± 0.10 4.16 ± 0.18 4.10 ± 0.14 4.12 ± 0.13 > 64K 6.16 ± 0.47 9.63 ± 0.23 10.00 ± 0.33 14.63 ± 0.14 > 256K 6.70 ± 0.09 12.98 ± 0.18 13.52 ± 0.15 32.30 ± 0.65 (2.38x) > 1M 6.99 ± 0.02 14.32 ± 0.67 14.84 ± 0.17 38.97 ± 1.03 (2.62x) > 2M 10.74 ± 0.29 64.25 ± 1.48 65.36 ± 1.00 64.97 ± 1.75 > > [1] https://lore.kernel.org/linux-mm/20260630-shivank-batch-migrate-offload-v6-0-da95d7e8b8a2@amd.com > > Applies cleanly on mm-new 10-07-26 (61cccb8363f). > > Signed-off-by: Shivank Garg > --- > Dev Jain (1): > mm/rmap: Add batched version of folio_try_share_anon_rmap_pte This would ideally be based on Dev's series instead if including a patch from his series. -- Cheers, David