From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 966C6ECD6F0 for ; Thu, 12 Feb 2026 08:44:25 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E15DB6B0005; Thu, 12 Feb 2026 03:44:24 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id DC4116B008A; Thu, 12 Feb 2026 03:44:24 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C7B0E6B008C; Thu, 12 Feb 2026 03:44:24 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id B5A806B0005 for ; Thu, 12 Feb 2026 03:44:24 -0500 (EST) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 7C9FC5A358 for ; Thu, 12 Feb 2026 08:44:24 +0000 (UTC) X-FDA: 84435168048.26.AABDE3E Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf26.hostedemail.com (Postfix) with ESMTP id 994B1140006 for ; Thu, 12 Feb 2026 08:44:22 +0000 (UTC) Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=jHj8cwZU; spf=pass (imf26.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1770885862; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=UTuLD0NRsdMObtunY4YwTBRtXGkzq2yALwbLzqMDPTk=; b=RswMBkjLfqozht2Fosr2o2rYldWcu+NpSmyJ03M2D7lfwJ8STa/o/DZuaz7/LH27GqO8VZ U6fzU+seJoCRNdzVWYtdDFGxK4Z8ARA2s+Iu72GjxyCdW2J7Ql4p1/h0O334NAQHqfSyfP Gzviz+UNmOZME6Q/pqrQuBQtWlfzzdo= ARC-Authentication-Results: i=1; imf26.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=jHj8cwZU; spf=pass (imf26.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1770885862; a=rsa-sha256; cv=none; b=JwCdXtcOLX/jOeIiuePO0iZ21G+nWhbj3EFa+x5tzv3vzmyQKdBaay3uQZPpXnYDJcTVIv pAwJb963CsvQN7ioK+7BwxlYA5Cl0GnojyILRNyLd2d5+szeVsFhmDRHB8U0TRWZN8Qhcc f/I+1dxmNvS+BRXOBoDzgQ+kMBV7RZw= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 7E8AB41899; Thu, 12 Feb 2026 08:44:21 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9DB23C4CEF7; Thu, 12 Feb 2026 08:44:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770885861; bh=khUwfsZrCJeC8y4xyRj4Ta7Ac2JXcbhabpcmZ5/6mug=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=jHj8cwZUzt0P3rDlFMaOsNHcHv1Al+LMyPc/k6q6ykwZi4kyKp3s1y/ZtiNbK7KEE TFX+QBPCAfcJUJqGriUD1eyQbifA4Fj6qBN0q13+DAKcIU9C9G3LHSEO3ScJzArasX 5n4M4Z69hgXfG1xyXt5jmCNA3Vzbxny9+APfwTaPcspnnCgbSsI0PueSqFc/Mza6yH 0q8g+w0waGkFqNxgmLQSoy1fYxaAbXN2lYaoh7oJ3kB77lKXS6KYHzYxt1nhEwrbhF +Sc8r/SWET+rWXG5aqU4pzhnX7RN1S5uF1g0kFWD2Q7RwYo+sdMDkHW5NLzXdacZ2o E1coVw02xqjXg== Message-ID: <3571cf8b-9fb3-41b2-a402-a8537ee2c399@kernel.org> Date: Thu, 12 Feb 2026 09:44:13 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHv2] mm: khugepaged: make scan loops suspend aware To: Sergey Senozhatsky Cc: Andrew Morton , Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260211031512.261127-1-senozhatsky@chromium.org> <104bc764-5a20-4ac2-95a8-b31f41255766@kernel.org> 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; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: ae5uhtz7xe5k8k76uyr5fkxykomtc5m5 X-Rspamd-Queue-Id: 994B1140006 X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1770885862-793762 X-HE-Meta: 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 z2Da2+GO FLUQojKjN7oH3++vhQVbIGWSEABxeoAzL2Fi+o1hon14S1oBXcpaDEvcI64sA4MvpKjnnzpjglmF4bTxxtPNslC36EOkvTDJjJX2WeSbruPy+jR8YLjSNv5US4jjVn7ACYfov/WcGfOb3QPLEj88fIZP2jaEg+cAHBi1+/aQ7tuMZPpuRDd85wvQMXb92tZ32U/VGJ912FJ1geSjCjBF5kBxWMcKOVfxaxD0FMxiluYWKtYb2psVu1P90+b7rriYCJ8rhMHVQnkVraxEEF2y6Lw8MAIYUgINYWn/XYlbjXGg0O3v11I2aDEEHqw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2/12/26 07:32, Sergey Senozhatsky wrote: > On (26/02/11 10:50), David Hildenbrand (Arm) wrote: >> On 2/11/26 04:15, Sergey Senozhatsky wrote: >>> A number of khugepaaged's loops, e.g. khugepaged_scan_mm_slot(), >>> are time unbound, which can become problematic during system >>> suspend: >>> >>> PM: suspend entry (s2idle) >>> Filesystems sync: 0.003 seconds >>> Freezing user space processes >>> Freezing user space processes completed (elapsed 0.003 seconds) >>> OOM killer disabled. >>> Freezing remaining freezable tasks >>> Freezing remaining freezable tasks failed after 20.004 seconds (1 tasks refusing to freeze, wq_busy=0): >>> task:khugepaged state:D stack:0 pid:1345 ppid:2 flags:0x00004000 >>> Call Trace: >>> >>> schedule+0x523/0x16a0 >>> schedule_timeout+0x23b/0x6e0 >>> io_schedule_timeout+0x3f/0x80 >>> wait_for_completion_io_timeout+0xe4/0x170 >>> submit_bio_wait+0x79/0xc0 >>> swap_readpage+0x150/0x2d0 >>> swap_cluster_readahead+0x3be/0x750 >>> shmem_swapin+0xa7/0x100 >>> shmem_swapin_folio+0xcd/0x2e0 >>> shmem_get_folio+0x237/0x580 >>> collapse_file+0x247/0x1280 >>> hpage_collapse_scan_file+0x26e/0x380 >>> khugepaged+0x43b/0x810 >>> kthread+0xfb/0x120 >>> >>> >>> Make hpage_collapse_test_exit_or_disable() suspend aware so >>> that khugepaaged's scan loops can terminate in a timely manner >>> and let system enter the sleep state. >>> >> >> Do we want a Fixes: tag, and maybe backport this to stable kernels? > > I can Cc stable, but I don't know about Fixes - we are adding something > that was never there, not fixing a regression. Cc: stable is only possible with a valid Fixes:. If we're fixing an issue, we usually try to identify which commit introduced the issue. For example, support for freezing was introduced in commit 878aee7d6b5504e01b9caffce080e792b6b8d090 Author: Andrea Arcangeli Date: Thu Jan 13 15:47:10 2011 -0800 thp: freeze khugepaged and ksmd It's unclear why schedule friendly kernel threads can't be taken away by the CPU through the scheduler itself. It's safer to stop them as they can trigger memory allocation, if kswapd also freezes itself to avoid generating I/O they have too. Now that I am looking through the history, I find: commit b39ca208403c8f2c17dab1fbfef1f5ecaff25e53 Author: Kevin Hao Date: Wed Dec 20 07:17:53 2023 +0800 mm/khugepaged: remove redundant try_to_freeze() A freezable kernel thread can enter frozen state during freezing by either calling try_to_freeze() or using wait_event_freezable() and its variants. However, there is no need to use both methods simultaneously. The freezable wait variants have been used in khugepaged_wait_work() and khugepaged_alloc_sleep(), so remove this redundant try_to_freeze(). I used the following stress-ng command to generate some memory load on my Intel Alder Lake board (24 CPUs, 32G memory). I wonder if that made the issue more likely to appear? Interestingly, we also had in the past: commit 1dfb059b9438633b0546c5431538a47f6ed99028 Author: Andrea Arcangeli Date: Thu Dec 8 14:33:57 2011 -0800 thp: reduce khugepaged freezing latency khugepaged can sometimes cause suspend to fail, requiring that the user retry the suspend operation. So it's a recurring theme. Given that we only scan "khugepaged_pages_to_scan" pages/ptes/etc. before going back to sleep, I wonder how that can take in your setup that long. Why does it end up taking something around 20 seconds in your setup? How is khugepaged_pages_to_scan set in your environment? -- Cheers, David