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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 173E6C369A5 for ; Tue, 8 Apr 2025 18:18:44 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 0661C6B00B7; Tue, 8 Apr 2025 14:18:42 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 017246B00B9; Tue, 8 Apr 2025 14:18:41 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DD3CB6B00BB; Tue, 8 Apr 2025 14:18:41 -0400 (EDT) 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 BF3DA6B00B7 for ; Tue, 8 Apr 2025 14:18:41 -0400 (EDT) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id D6FAD1A146F for ; Tue, 8 Apr 2025 18:18:42 +0000 (UTC) X-FDA: 83311687284.05.02C6BDE Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf01.hostedemail.com (Postfix) with ESMTP id A77C24000A for ; Tue, 8 Apr 2025 18:18:40 +0000 (UTC) Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=a3tEIf5o; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf01.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1744136320; a=rsa-sha256; cv=none; b=Us+mUYg/tpbBiyQkyLnEMTwb31iH9kmqIKJxTURshOfHa/AOOh9wQ1X89N/0hFkLA2QkjO xOeEVJPlpgIP8+M5ZUoDv8PJQ1kZbZmLI56BWKdSFGtvbR5ZjFC9cPzaR1iJzY6so4jIDv Pg2iThocDkwFAAaO/mEpIHZpitdqq3U= ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=a3tEIf5o; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf01.hostedemail.com: domain of david@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1744136320; 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=a5MNTcQLVVXVMARql3CFcEx28D/XK8NJIFEW1cH0fos=; b=vJVOfWgxmD2whsJrVgsIwDZirc56q3pkRHsxzgk7CEwFcWas+WW/wW1Q0XtyqWxbjozdAI Y+OUEk6fsSe8KRjT6ipz55wbokpG+l1PpMF3C7q347GPvJ1qIDgVSB1MQdYDb+J7z0NvqM phZH1iKschmYTssiUmu5lDiz6vtEwqQ= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1744136320; h=from:from: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:autocrypt:autocrypt; bh=a5MNTcQLVVXVMARql3CFcEx28D/XK8NJIFEW1cH0fos=; b=a3tEIf5oKiW8ZtT2gfpSq1LBkMZMqc51MPJoHR0Ped3ECoIB5UwX51zs0+Mw93ZPY6B4Kv XhZRyY5lVus5E4vJBbnyDcK5VQZ+biZs4ltn9p4kPGYzYmp1p3HMTp+8b7QPeMgEzB0/GY ysOg0SFgt3SZ9wHbCiHtncN8zoho7RI= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-389-VWa0F7mmNLW60vUkgZOplg-1; Tue, 08 Apr 2025 14:18:38 -0400 X-MC-Unique: VWa0F7mmNLW60vUkgZOplg-1 X-Mimecast-MFC-AGG-ID: VWa0F7mmNLW60vUkgZOplg_1744136317 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-43ceeaf1524so34060915e9.1 for ; Tue, 08 Apr 2025 11:18:38 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1744136317; x=1744741117; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=a5MNTcQLVVXVMARql3CFcEx28D/XK8NJIFEW1cH0fos=; b=dMmwbBF+Ag4EQxDBoQPzosGGPyDOGnRu38MVzbxgc1hpK2sLX02PqpCVqjASjzq4oM I7bA5Fepqsd0DE4XtIsPZ895r1VRAngmjbFhOz2fQgT/XVi+NZ03j2i/yJesVKXWsq5y 2L7x+ns6lD96Wx27vatuj7t/WaQDFITaZ1U1rJgcuL9xmrzvnePsYIQ43b9B5vnWg2g7 Ii1msNplmwvL/arank3n4q7TrOoS47J3MLgBiyISTfMn5VZgmYoWffOeuRZlghnPXoq6 AdUzrMNPp9duzpFLmGAAf2Y0JyV5NBcsjzZWbyyPDKCZmH+oPRfB7Bu6Dc28lv6Hf1fC zWIw== X-Forwarded-Encrypted: i=1; AJvYcCVY6fkdop2hNgQemNBifAOl3ARdVddKxypzAzUIs/0Uq2oozrSHT6Eu2rLNDjDJ6LsawBCtezL4fA==@kvack.org X-Gm-Message-State: AOJu0Yxplb2FIRfrENyVIsqIzWFKDlMNVTv+N8LUhlxq6+jZqHPYUeYx ke5fYivMRYV1ZcbuAdHtLAOm9yNeoSWMIiVK/vtxVxWPIffaEFA2yB5eXKhXoqmfegSRZ/GKl6l T/rwo+8KcTXAypC3G2dGrZZsU0eip+bBmo0Kwn6hmPcylenJU X-Gm-Gg: ASbGncsBUyIckvtRZAlynnUtw/uBToJrHZqR7iqr30ZIQOJao894GkyEA6o1STfggJ1 qcqSUYfBPOFK6alu9a5rhyGVbySh60mAFioOINgIN9SHTX/g4MBmjl0cee4gM9SwDJl3dofhJv0 CrnBl1ik+3DYD+Bn5I3w+6xZaYZhCDxq3h0H7BrmbBqJtzDLBbfIGOP8KIe1eixUojBAn+vHRg7 c9zdMV6T/MmZ43jSmgay5zjt4v34L6fWD/g/V9chFaDSbiOuCmV0BgqAv+lUnpii+Tai8PBw35q JjLsr4naMvA6YPe02YPqJkyVC5hb/0Y+4PXw8+E0uSdMiJwXFx0ef10L3mL7EDqM+fHz1P+hS33 dzBFnbijEoq2pEDyOZAZgr+hwy8rrC3aDQfHDtCGE X-Received: by 2002:a05:600c:cc7:b0:439:9737:675b with SMTP id 5b1f17b1804b1-43f1ef4ed59mr687735e9.7.1744136317499; Tue, 08 Apr 2025 11:18:37 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHHt6LtzhtOCodKlEDsv24JUxo5GCvyjuPDd1u+OK+hcqeg+gGGG7/Q1UKS8qILxl7CGg59mw== X-Received: by 2002:a05:600c:cc7:b0:439:9737:675b with SMTP id 5b1f17b1804b1-43f1ef4ed59mr687595e9.7.1744136317185; Tue, 08 Apr 2025 11:18:37 -0700 (PDT) Received: from ?IPV6:2003:cb:c707:4f00:a44a:5ad6:765a:635? (p200300cbc7074f00a44a5ad6765a0635.dip0.t-ipconnect.de. [2003:cb:c707:4f00:a44a:5ad6:765a:635]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43ec1630ddesm172061645e9.5.2025.04.08.11.18.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 08 Apr 2025 11:18:33 -0700 (PDT) Message-ID: <60ae4d6b-3ace-482b-9945-1261003f3785@redhat.com> Date: Tue, 8 Apr 2025 20:18:32 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/3] mm,slub: Do not special case N_NORMAL nodes for slab_nodes To: Vlastimil Babka , Harry Yoo Cc: Oscar Salvador , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Jonathan Cameron , linux-cxl@vger.kernel.org References: <20250408084153.255762-1-osalvador@suse.de> <20250408084153.255762-2-osalvador@suse.de> <92ff4f7f-90d2-48ab-8f7d-7fc3485276b5@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 2tBG5gKYxUJix9siyY33wX6fr9JiRcZ-rQLwm3FAF70_1744136317 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: A77C24000A X-Stat-Signature: 73e4r6xswdphbfqwgc55nzkkgyrd8fck X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1744136320-985331 X-HE-Meta: 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 xuOTQDPZ l6sV8PG8kquLrpKcBiHMJTwGFhhd7UUC0+4pex5K2RGjVfY2iKByNcRaHYKzmB7sOZ6DylvKfIEWAnTK5VyRW3jN5/Xp2RzkDgKrdWEboxVY7VCXQDZ+vLOotzg== 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 08.04.25 19:55, Vlastimil Babka wrote: > On 4/8/25 16:25, David Hildenbrand wrote: >> On 08.04.25 16:18, Harry Yoo wrote: >>> On Tue, Apr 08, 2025 at 12:17:52PM +0200, David Hildenbrand wrote: >>>> On 08.04.25 10:41, Oscar Salvador wrote: >>>>> Currently, slab_mem_going_going_callback() checks whether the node has >>>>> N_NORMAL memory in order to be set in slab_nodes. >>>>> While it is true that gettind rid of that enforcing would mean >>>>> ending up with movables nodes in slab_nodes, the memory waste that comes >>>>> with that is negligible. >>>>> >>>>> So stop checking for status_change_nid_normal and just use status_change_nid >>>>> instead which works for both types of memory. >>>>> >>>>> Also, once we allocate the kmem_cache_node cache for the node in >>>>> slab_mem_online_callback(), we never deallocate it in >>>>> slab_mem_off_callback() when the node goes memoryless, so we can just >>>>> get rid of it. >>>>> >>>>> The only side effect is that we will stop clearing the node from slab_nodes. >>>>> >>>> >>>> Feel free to add a Suggested-by: if you think it applies. >>>> >>>> >>>> Do we have to take care of the N_NORMAL_MEMORY check in kmem_cache_init() ? Likely it >>>> would have to be a N_MEMORY check. >>>> >>>> >>>> But, I was wondering if we could get rid of the "slab_nodes" thingy as a first step? >>> >>> The following commit says that SLUB has slab_nodes thingy for a reason... >>> kmem_cache_node might not be ready yet even when N_NORMAL_MEMORY check >>> says it now has normal memory. >> >> node_states_set_node() is called from memory hotplug code after >> MEM_GOING_ONLINE and after online_pages_range(). >> >> Pages might be isolated at that point, but node_states_set_node() is set >> only after the memory notifier (MEM_GOING_ONLINE) was triggered. >> >> So I don't immediately see the problem assuming that we never free the >> structures. > > Hm, I think it still exists. So consider: Ah, now I understand the problem, thanks for pointing that out. > > - slab_mem_going_online_callback() creates kmem_cache_node for the new node > for existing caches under the mutex > > Then a cache creation races with "node_states_set_node() is set only after > the memory notifier (MEM_GOING_ONLINE) was triggered" in a way that it > doesn't see the node set yet - kmem_cache_node for the new node on the new > cache will be missing. > > The root issue is node_states_set_node() doesn't happen under slab_mutex. > slab_nodes update happens under the slab_mutex to avoid this race. We could by grabbing the mutex in MEM_GOING_ONLINE and putting it in MEM_CANCEL_ONLINE / MEM_ONLINE when a node is going online. We use something similar in virtio-mem code to sync over the whole onlining period. Of course, if someone would try creating a cache from inside a notifier, it would be problematic. (unlikely, but pointing it out) Onlining a node is not a particularly common operation, so maybe ... good enough. Let me think about other alternatives that require minimal adjustments. -- Cheers, David / dhildenb