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 1841628B4FA for ; Mon, 16 Feb 2026 09:24:56 +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=1771233897; cv=none; b=qHVkpwchgIZjVMbXGDlddpgS9MF/HkEqw5Q/5rLjIHEf+K2m/oWgx87q3PgTU6ZfMKxrVgyqWo3/t/TD1giyH71RtkKWT1yghSnM9PZnYBY2aTtIjQtiwtLmQ+ibscR37Ox7fxRRm69+5MfOtqPATzKnBlaMOosCjB+hD4grM+U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771233897; c=relaxed/simple; bh=OR2VlSMVusMINq3vcBxMFK8Q/cZKx7EE1BOEdHfWSVc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ZPLAeHfmJcI9jNr7Njfea+MElPv2ZJf4s0zmWrOe8WKR7nDv3sLfnK83kClK/puHmzwnL3B/uz7g7fydh7i/vNCJDqQRE2DRoTyw9xuistHIRAaF0rdtIv6sh8jhdjxWJfI4/UvatzJ52g6QbCuFU4dyqQBm/fv7OcVk6WIkwsI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=cbRO1+70; 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="cbRO1+70" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9A990C116C6; Mon, 16 Feb 2026 09:24:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771233896; bh=OR2VlSMVusMINq3vcBxMFK8Q/cZKx7EE1BOEdHfWSVc=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=cbRO1+70oWXH/C99sJCpa45wqu0YDJge1ODTJGcfhNN37WUNRjQAkwfNJms/pxt4a 4SYqV6HR6durRaV0LwCV7oXw8xOdkOihG2qUVmUUGhqQ4wZEIiMSjk91T/hGafljB9 vUnd56CmpXxNZC0B+PJpC+w+bC7Vp43N1tlJm9/kIC/jU8VYpp082cnntQoF1Wc6qU 1DcLjupiBrvqgY4FPLdZ/EuHjtGjwVEg1y6aRB8ImJxTVMQVgm9cIZvsTgHq+I33MX Nk2vYnMFbzOeMutD2wA6arpIpIfirD15dJyOUdf4r+13nFCB/KQorFDhhUz7BTJbKn jg0O/tTuAqXYw== Message-ID: <5dc7d3a2-a358-481d-9352-d8356d3343c2@kernel.org> Date: Mon, 16 Feb 2026 10:24:49 +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: [PATCHv2] mm: khugepaged: make scan loops suspend aware To: Lance Yang , Sergey Senozhatsky Cc: Andrew Morton , Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260211031512.261127-1-senozhatsky@chromium.org> <104bc764-5a20-4ac2-95a8-b31f41255766@kernel.org> <3571cf8b-9fb3-41b2-a402-a8537ee2c399@kernel.org> <16ce9ce2-8081-482c-a6ea-0932ebd081f1@kernel.org> <56345542-544a-48e4-b127-49a850deee9b@linux.dev> 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: <56345542-544a-48e4-b127-49a850deee9b@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2/14/26 07:35, Lance Yang wrote: > > > On 2026/2/12 17:10, David Hildenbrand (Arm) wrote: >> On 2/12/26 10:05, Sergey Senozhatsky wrote: >>> [..] >>> >>> Interesting, so 1dfb059b9438633 and 878aee7d6b5504e fixed real >>> problems "khugepaged can sometimes cause suspend to fail", but >>> I don't see what exactly b39ca208403c8f2 fixed.  Sounds more >>> like an "optimization"? >> >> Yes, a cleanup. I wonder if it caused harm. >> >>> >>> >>> I only have bug reports at hands, I don't have a repro.  Can the fact >>> that swap reads require S/W decompression (zram) add enough latency? >> >> I guess so. 20 seconds is still a lot. >> >>> >>> >>> Let me check. >>> >>> cat /sys/kernel/mm/transparent_hugepage/khugepaged/pages_to_scan >>> 4096 >>> >>> Hmm, doesn't sound too high.  Let me look more. >> >> Yeah, that's not a lot of pages to scan. It's the default (8 * >> HPAGE_PMD_NR) > > Right. 4096 pages is not much to scan :) > > This patch lets khugepaged be frozen between VMAs. > > But if khugepaged is already collapsing when freeze starts, there > are two places without freeze checks that could take a bit long: > > - __collapse_huge_page_swapin() loops 512 pages, calls do_swap_page() >   for each swap entry. > > - collapse_file() loops 512 pages, calls shmem_get_folio(). If pages >   are swapped out, shmem_swapin_folio() is called. > > Each swap-in can block for I/O. With multiple pages swapped out, the > cumulative time adds up. But 20 seconds to swap in 4096 pages (16 MiB)? Okay, on arm64 with 64k it would be a lot more (8 * 512 MiB == 4 GiB). With With 16k we're at 8 * 32MiB = 256 MiB. > > Maybe we also need check points inside these loops to bail out early? I'd only do that if we have evidence that it's actually helpful. @Sergey, with which base page size are you running (4k vs. 16k vs 64k)? I assume your report is on aarch64, correct? -- Cheers, David