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 A8DD1CDB471 for ; Mon, 22 Jun 2026 07:12:49 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 39FB76B0088; Mon, 22 Jun 2026 03:12:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 350E36B008A; Mon, 22 Jun 2026 03:12:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 23FD36B008C; Mon, 22 Jun 2026 03:12:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id E860A6B0088 for ; Mon, 22 Jun 2026 03:12:47 -0400 (EDT) Received: from smtpin30.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 719FBA057F for ; Mon, 22 Jun 2026 07:12:47 +0000 (UTC) X-FDA: 84906681174.30.BB9961C Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf21.hostedemail.com (Postfix) with ESMTP id BD03E1C0003 for ; Mon, 22 Jun 2026 07:12:45 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=L4PNXIa9; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf21.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1782112365; 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=JPDKWUY1v1INodMedwDx7DwR6GeDNvta1xVixbP8aME=; b=k7Ba1InMoVYa3kva14LAMiDcltRDj+htSQFnegkk+jFsMWXIz6VCsDxluz1eJ5Z/T4XZIS ocW6JYTdXj4e59+kXwImXuZ70tUlwHBZEjtyGNXERMTpBkAPqMiWbzFRNGHvF6JFobfgKR G8t/phBixisyBdeTJFBV5X9PqQie2II= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1782112365; b=n1v3xDAUhi97db0XgapBZfNADioxslWAuUi8pkDDiKwmum5XNHwU3B7qAbUgHGIUYsFl8S Qe8Q+/Uh7TkH0JoWTZBruxfdZiAfCQWuW5BOQ1rYux+sruxC39pTPkY5GwPK2P49dQ3Sz3 lnTO1AC1DDFSXGHmCOqvgpB805aDxpo= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=L4PNXIa9; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf21.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 129C4600AF; Mon, 22 Jun 2026 07:12:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 83A371F000E9; Mon, 22 Jun 2026 07:12:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782112364; bh=JPDKWUY1v1INodMedwDx7DwR6GeDNvta1xVixbP8aME=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=L4PNXIa9Zw4w4w825y5AbRuIkOOgKjEMz0H/IY6pmo0/6ndTOJFPljNEwX3AL7dbj plw6zBxzTfQaZ/UroLuI54iZKHPFrPnF3lAqPwgK92ea6EP595egePsMrZLYbUJJoU 168UWkvIZs2O/Ux0HkhEJiGWOLIT53MX63q3eL8x0Hhha674hOrFnrSs35GDOW2/Lx CSSgZC2lV8LlJN/6+qpsxBWDeUwGAGbcZWTnr89VN2ut3cW8PKou1Rl9C1+nzzIlw5 6g7rbChB8u464k5hXQt7m1oerM34BEUDf/rr49Uy6trcC8HiyUQtylGI43wb1argWM rOa11sg/oUJ/w== Message-ID: Date: Mon, 22 Jun 2026 09:12:38 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] cgroup/cpuset: rebind mm mempolicy to effective_mems, not mems_allowed To: Waiman Long , Gregory Price Cc: Farhad Alemi , Andrew Morton , Farhad Alemi , Yury Norov , Joshua Hahn , Zi Yan , Matthew Brost , Rakie Kim , Byungchul Park , Ying Huang , Alistair Popple , Rasmus Villemoes , linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, stable@vger.kernel.org References: <8d3b4561-92cd-4ebc-8462-5fb0fd659e8a@kernel.org> <70f486ce-5ef6-4d72-8cc3-7086f4eea930@redhat.com> <51eafe6c-6622-479b-b391-6d3ff9350e75@kernel.org> <38578aea-61c3-4328-aee9-8e7421672647@kernel.org> <9d8b650d-6faa-425a-8db7-1e206cb25158@redhat.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: <9d8b650d-6faa-425a-8db7-1e206cb25158@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: BD03E1C0003 X-Rspam-User: X-Stat-Signature: b51tnckhwzj7xrhqc6xok8azireb6mcj X-HE-Tag: 1782112365-235227 X-HE-Meta: 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 z6J6n/01 K6gnJDUjbdQzxU1YSF8nz6tB1BKMiI8DBeVjYKYA3xTQdJunNi6F7OLtR9/Z/ef1qCWW6u90TePt1BHE6OMgbaOVb5epvKG7Em55SJew9NTdeKlezzJSLbMux5wYOqSEOEfVS5LgHx1xDRVlrUoYNlNRojm54G/EPfJrSlyH3MDBAxkXYUoH9tp/Ebo9lLvg7wcMkEMWhX1mzvXSvZkhHDIYwKF7gUv2fasXvjU6CswlrUkVhUkhBGwyLaZhVGfNsYaNMQsBPdQUwdsX6KI1Mmk3HKhs+42Kr//jbSjfNC/RuNErxSmQ5hPwMCcvt2v30CBYvQmG4axhhH6MHNwjJ4+itCDd8lZpKKe5ZOi41AiCsBMXIUsDAhNu7ck93ZY1Us1qIDvcxrFpQzxy26pazkrfZkg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/21/26 05:24, Waiman Long wrote: > On 6/18/26 4:41 AM, David Hildenbrand (Arm) wrote: >> On 6/16/26 17:23, Waiman Long wrote: >>> Yes, taking newmems is a reasonable choice and there are pros and cons with each >>> options. My focus is more on not changing how v1 cpuset behaves as it is well >>> defined in the v1 cpusets.rst file: >>> >>>      Requests by a task, using the sched_setaffinity(2) system call to >>>      include CPUs in its CPU affinity mask, and using the mbind(2) and >>>      set_mempolicy(2) system calls to include Memory Nodes in its memory >>>      policy, are both filtered through that task's cpuset, filtering out any >>>      CPUs or Memory Nodes not in that cpuset.  The scheduler will not >>>      schedule a task on a CPU that is not allowed in its cpus_allowed >>>      vector, and the kernel page allocator will not allocate a page on a >>>      node that is not allowed in the requesting task's mems_allowed vector. >>> >>> v2, OTOH, is more vague as to what setting cpuset.mems will mean and we >>> generally follow what v1 is doing, but we have more leeway of what we can do. >>> >>> Using newmems will make the above text not totally correct. At least the offline >>> memory nodes will be filtered out which will not be utilized by the task when >>> the offline node becomes online. That is why I am saying that we will have to >>> correct the documentation if we want to make this change. >> So IIUC: >> >> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c >> index 1335e437098e..cdfc615f35a5 100644 >> --- a/kernel/cgroup/cpuset.c >> +++ b/kernel/cgroup/cpuset.c >> @@ -2645,7 +2645,13 @@ void cpuset_update_tasks_nodemask(struct cpuset *cs) >>                    migrate = is_memory_migrate(cs); >>   -               mpol_rebind_mm(mm, &cs->mems_allowed); >> +               /* >> +                * For v1 we can have empty effective_mems, but we cannot >> +                * attach any tasks (see cpuset_can_attach_check()). For v2, >> +                * it's guaranteed to not be empty. >> +                */ >> +               VM_WARN_ON_ONCE(nodes_empty(cs->effective_mems)); >> +               mpol_rebind_mm(mm, &cs->effective_mems); >>                  if (migrate) >>                          cpuset_migrate_mm(mm, &cs->old_mems_allowed, &newmems); >>                  else > > That is true, but I don't think we need a VM_WARN_ON_ONCE() here. I'd prefer if we catch such stuff in the future more easily than running into late divide-by-zero. Maybe we should check in mpol_rebind_mm() instead. -- Cheers, David