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 D996EC87FCB for ; Tue, 5 Aug 2025 09:58:21 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 699416B0095; Tue, 5 Aug 2025 05:58:21 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 670826B0096; Tue, 5 Aug 2025 05:58:21 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 55F236B009A; Tue, 5 Aug 2025 05:58:21 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 472706B0095 for ; Tue, 5 Aug 2025 05:58:21 -0400 (EDT) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id C70C21355F5 for ; Tue, 5 Aug 2025 09:58:20 +0000 (UTC) X-FDA: 83742253560.28.054BAF5 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf27.hostedemail.com (Postfix) with ESMTP id DCE3B40006 for ; Tue, 5 Aug 2025 09:58:15 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=Isu8XnYg; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf27.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1754387897; a=rsa-sha256; cv=none; b=CbKKY3CWkQaXirxXBF2zSOX5N1LMMlsmi9mhf1lqotOawbCRFhU+1fYX7rg/+Y6XkFdorW Ve7ixHJFPX1yeJJM65kpr8zqPD+xXK8FEeLZrDHH0CPnEs7X2OPVuxtuPCaOoZN2MstY+B zMnzSHkyS8pyJ4/OKxKaJcU9JwVfbpg= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=Isu8XnYg; dmarc=pass (policy=quarantine) header.from=redhat.com; spf=pass (imf27.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 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=1754387897; 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=zm/u8bmVSBWBP7KMq+8GNg/jH0DTBhPVQW1hnHzNiv8=; b=hJByC4ZJH8h9t1TI3+cP2T1sCUezYe4QWSU2Blo7x3Wn3LwaV9iSXlm8KNixA4YTsWHp1j VBj061Jnm8H590N6Sb+gAdby7HBt7G0wl3Aevv+iZPcfxh8yHQynKxqRBSJM1C18REoeLl yfyUsmtZq/ncoCI2C4O6zSjCuY5+FQk= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1754387895; 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=zm/u8bmVSBWBP7KMq+8GNg/jH0DTBhPVQW1hnHzNiv8=; b=Isu8XnYggxaBh4yPf1FgNEmE1IFo9+tImEr4CTacd0NqXiuL0xLsY47XBMSEADeHu4MDSp 3tlJdZfvEFdscJk+H+9RJe9auB3VSeGo4A0HIvTmOFnNKFMBPla7M+38bPmo8MpuOh02XM BsKbrU3+i+lYIbqDstmTmazYa0FSR2Y= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-652-9KZoJuHePFOzIxnVjzJxzw-1; Tue, 05 Aug 2025 05:58:14 -0400 X-MC-Unique: 9KZoJuHePFOzIxnVjzJxzw-1 X-Mimecast-MFC-AGG-ID: 9KZoJuHePFOzIxnVjzJxzw_1754387893 Received: by mail-wm1-f70.google.com with SMTP id 5b1f17b1804b1-459e30e4477so2804455e9.1 for ; Tue, 05 Aug 2025 02:58:13 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1754387893; x=1754992693; 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=zm/u8bmVSBWBP7KMq+8GNg/jH0DTBhPVQW1hnHzNiv8=; b=XEnogDpXCAGtyYQVFy7keVqgtubWsNxCgMyMh/Lo93jFgdf++IIctoGgbJA/FZ10Z1 a10DCnbQw0W5Q5D4L8LGYEx0UQrESlBVns+gL0tIcBb4Dohe7jbg/3/3zoKHx4Y39XNe D4cJP2rO/KXrSPM6W9Rx+dVY40pTxlYW/26hqJmygggOxsKuzRFD3vitWSGt8EO9Mto3 ULnfk/Mor067n3N8S0UEhA0oH0Fviv52PDPSlDLf4iIetwK2oREL3aMgx1RCfRloMygf QQ0z4ruEql+GBqt+F/iANnKen4Rk6CqLlbe0MLNeiatFnOAsIKjzgXXxwMk2hHihuJnL SEYg== X-Forwarded-Encrypted: i=1; AJvYcCUwxEeWnJ9poSpssNRXDGd2P5Ab8kDOO0wRLxaq5pvaHZXPTJk2wuHjBh9KVJekZJoDMo/GiJR97A==@kvack.org X-Gm-Message-State: AOJu0Yxrc4sCO+jIE9ZZXS0bmwaHswH4rowlANNIl5XndYEH7O2RxXh7 nnUF3vcB9a4kkASPKT1iQbxR6hcXQPV3Rbj7tD57i5fgUMCSMcYOKszOC3RDLjIkpCcIp5vz1je lt0P4mY3/rbIjHyBPkp5b4Hp+OEdOdkuGenlF5niEUgpFJCL1SVl0 X-Gm-Gg: ASbGncu+jrWzG8I7l3cbgVT/imE07VNfDFWxm864G8L6HJpwFQcTn1U5M9RFwNS7Ugw mlsqeEuTi5R7l4mxHA3T5OepR4QysIVir054cbD0EV068ymepNuzgmMSPHZLKP7i2Kz8hAfbuhs e1rcKQOgvuVgSL1PgjupRf3tSkduN9GjM3p432TzY77bRfmmKd9nL5tNuTeABV1oMdshyyRKa+1 Sy6IR/4h6KxLW547rtpZ19YECXv6oRIN/uoVWXeKh6HSmEELY3it4gOWhT/jyB+B5Rpzkjqcfsf aPTDbvx5W9Dz73rkIh5VqtGonw0M0hA7dNZLQSIVN8lm72v63V+86kldALQwCMVvVapmGBg= X-Received: by 2002:a05:600c:4ecd:b0:459:e048:af42 with SMTP id 5b1f17b1804b1-459e048af80mr27344255e9.24.1754387892698; Tue, 05 Aug 2025 02:58:12 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHu9rgyjmk0uonkMuGZyFuLrvh1XIgvJwkQbJZTilgPx9GuSO2bLOzz+iugEJg9v4l3IBuIMg== X-Received: by 2002:a05:600c:4ecd:b0:459:e048:af42 with SMTP id 5b1f17b1804b1-459e048af80mr27343985e9.24.1754387892256; Tue, 05 Aug 2025 02:58:12 -0700 (PDT) Received: from [192.168.3.141] (p57a1a26f.dip0.t-ipconnect.de. [87.161.162.111]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b79c48de68sm18520294f8f.67.2025.08.05.02.58.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 05 Aug 2025 02:58:11 -0700 (PDT) Message-ID: <486c5773-c7fa-4e19-b429-90823ed2f7d5@redhat.com> Date: Tue, 5 Aug 2025 11:58:04 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH] mm/page_alloc: Add PCP list for THP CMA To: Juan Yescas Cc: akash.tyagi@mediatek.com, Andrew Morton , angelogioacchino.delregno@collabora.com, hannes@cmpxchg.org, Brendan Jackman , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org, Linux Memory Management List , matthias.bgg@gmail.com, Michal Hocko , Suren Baghdasaryan , Vlastimil Babka , wsd_upstream@mediatek.com, Zi Yan , Kalesh Singh , "T.J. Mercier" , Isaac Manjarres References: 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/g1oFAmgsLPQFCRvGjuMACgkQTd4Q 9wD/g1o0bxAAqYC7gTyGj5rZwvy1VesF6YoQncH0yI79lvXUYOX+Nngko4v4dTlOQvrd/vhb 02e9FtpA1CxgwdgIPFKIuXvdSyXAp0xXuIuRPQYbgNriQFkaBlHe9mSf8O09J3SCVa/5ezKM OLW/OONSV/Fr2VI1wxAYj3/Rb+U6rpzqIQ3Uh/5Rjmla6pTl7Z9/o1zKlVOX1SxVGSrlXhqt kwdbjdj/csSzoAbUF/duDuhyEl11/xStm/lBMzVuf3ZhV5SSgLAflLBo4l6mR5RolpPv5wad GpYS/hm7HsmEA0PBAPNb5DvZQ7vNaX23FlgylSXyv72UVsObHsu6pT4sfoxvJ5nJxvzGi69U s1uryvlAfS6E+D5ULrV35taTwSpcBAh0/RqRbV0mTc57vvAoXofBDcs3Z30IReFS34QSpjvl Hxbe7itHGuuhEVM1qmq2U72ezOQ7MzADbwCtn+yGeISQqeFn9QMAZVAkXsc9Wp0SW/WQKb76 FkSRalBZcc2vXM0VqhFVzTb6iNqYXqVKyuPKwhBunhTt6XnIfhpRgqveCPNIasSX05VQR6/a OBHZX3seTikp7A1z9iZIsdtJxB88dGkpeMj6qJ5RLzUsPUVPodEcz1B5aTEbYK6428H8MeLq NFPwmknOlDzQNC6RND8Ez7YEhzqvw7263MojcmmPcLelYbfOwU0EVcufkQEQAOfX3n0g0fZz 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+DWgUCaCwtJQUJG8aPFAAKCRBN3hD3AP+DWlDnD/4k2TW+HyOOOePVm23F5HOhNNd7nNv3 Vq2cLcW1DteHUdxMO0X+zqrKDHI5hgnE/E2QH9jyV8mB8l/ndElobciaJcbl1cM43vVzPIWn 01vW62oxUNtEvzLLxGLPTrnMxWdZgxr7ACCWKUnMGE2E8eca0cT2pnIJoQRz242xqe/nYxBB /BAK+dsxHIfcQzl88G83oaO7vb7s/cWMYRKOg+WIgp0MJ8DO2IU5JmUtyJB+V3YzzM4cMic3 bNn8nHjTWw/9+QQ5vg3TXHZ5XMu9mtfw2La3bHJ6AybL0DvEkdGxk6YHqJVEukciLMWDWqQQ RtbBhqcprgUxipNvdn9KwNpGciM+hNtM9kf9gt0fjv79l/FiSw6KbCPX9b636GzgNy0Ev2UV m00EtcpRXXMlEpbP4V947ufWVK2Mz7RFUfU4+ETDd1scMQDHzrXItryHLZWhopPI4Z+ps0rB CQHfSpl+wG4XbJJu1D8/Ww3FsO42TMFrNr2/cmqwuUZ0a0uxrpkNYrsGjkEu7a+9MheyTzcm vyU2knz5/stkTN2LKz5REqOe24oRnypjpAfaoxRYXs+F8wml519InWlwCra49IUSxD1hXPxO WBe5lqcozu9LpNDH/brVSzHCSb7vjNGvvSVESDuoiHK8gNlf0v+epy5WYd7CGAgODPvDShGN g3eXuA== Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 99PJRLx3qm2JZbnzR6aLOOxHeic7eAScQqT0U7AKWDY_1754387893 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: DCE3B40006 X-Stat-Signature: 4pieramuhw7qqrkct4dbq9axyt164ddn X-HE-Tag: 1754387895-156255 X-HE-Meta: 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 oZlywox5 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 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 05.08.25 03:22, Juan Yescas wrote: > On Mon, Aug 4, 2025 at 11:50 AM David Hildenbrand wrote: >> >> On 04.08.25 20:20, Juan Yescas wrote: >>> Hi David/Zi, >>> >>> Is there any reason why the MIGRATE_CMA pages are not in the PCP lists? >>> >>> There are many devices that need fast allocation of MIGRATE_CMA pages, >>> and they have to get them from the buddy allocator, which is a bit >>> slower in comparison to the PCP lists. >>> >>> We also have cases where the MIGRATE_CMA memory requirements are big. >>> For example, GPUs need MIGRATE_CMA memory in the ranges of 30MiB to 500MiBs. >>> These cases would benefit if we have THPs for CMAs. >>> >>> Could we add the support for MIGRATE_CMA pages on the PCP and THP lists? >> >> Remember how CMA memory is used: >> >> The owner allocates it through cma_alloc() and friends, where the CMA >> allocator will try allocating *specific physical memory regions* using >> alloc_contig_range(). It doesn't just go ahead and pick a random CMA >> page from the buddy (or PCP) lists. Doesn't work (just imagine having >> different CMA areas etc). >> >> Anybody else is free to use CMA pages for MOVABLE allocations. So we >> treat them as being MOVABLE on the PCP. >> >> Having a separate CMA PCP list doesn't solve or speedup anything, really. >> > > Thanks David for the quick overview. > >> I still have no clue what this patch here tried to solve: it doesn't >> make any sense. >> > > The story started with this out of tree patch that is part of Android. > > https://lore.kernel.org/lkml/cover.1604282969.git.cgoldswo@codeaurora.org/T/#u > > This patch introduced the __GFP_CMA flag that allocates pages from > MIGRATE_MOVABLE > or MIGRATE_CMA. What it happens then, it is that the MIGRATE_MOVABLE > pages in the > PCP lists were consumed pretty fast. To solve this issue, the PCP > MIGRATE_CMA list was added. > This list is initialized by rmqueue_bulk() when it is empty. That's > how we end up with the PCP MIGRATE_CMA list > in Android. In addition to this, the THP list for MIGRATE_MOVABLE was > allowed to contain > MIGRATE_CMA pages. This is causing THP MIGRATE_CMA pages to be used > for THP MIGRATE_MOVABLE > making later allocations from THP MIGRATE_CMA to fail. Okay, so this patch here really is not suitable for the upstream kernel as is. It's purely targeted at the OOT Android patch. > > These workarounds are mainly because we need to solve this issue upstream: > > - When devices reserve big blocks of MIGRATE_CMA pages, the > underutilized MIGRATE_CMA > can fall back to MIGRATE_MOVABLE and these pages can be pinned, so if > we require MIGRATE_CMA > pages, the allocations might fail. > > I remember that you presented the problem in LPC. Were you able to > make some progress on that? There is the problem of CMA pages getting allocated by someone for a MOVABLE allocation, to then short-term pin it for DMA. Long-term pinnings are disallowed (we just recently fixed a bug where we accidentally allowed it). One concern is that a steady stream of short-term pinnings can turn such pages unmovable. We discussed ideas on how to handle that, but there is no solution upstream yet. -- Cheers, David / dhildenb