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(p200300d82f372b00948cdd9f29c873f4.dip0.t-ipconnect.de. [2003:d8:2f37:2b00:948c:dd9f:29c8:73f4]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45b814da51esm145663325e9.8.2025.09.01.11.38.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 01 Sep 2025 11:38:39 -0700 (PDT) Message-ID: <776629b2-5459-4fa0-803e-23d4824e7b24@redhat.com> Date: Mon, 1 Sep 2025 20:38:37 +0200 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: [RFC 0/3] cgroups: Add support for pinned device memory To: =?UTF-8?Q?Thomas_Hellstr=C3=B6m?= , Maarten Lankhorst , Lucas De Marchi , Rodrigo Vivi , David Airlie , Simona Vetter , Maxime Ripard , Natalie Vock , Tejun Heo , Johannes Weiner , =?UTF-8?Q?=27Michal_Koutn=C3=BD=27?= , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Lorenzo Stoakes , "'Liam R . Howlett'" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Thomas Zimmermann Cc: Michal Hocko , intel-xe@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org References: <20250819114932.597600-5-dev@lankhorst.se> <9c296c72-768e-4893-a099-a2882027f2b9@lankhorst.se> From: David Hildenbrand Content-Language: en-US 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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+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: 8bit On 01.09.25 20:21, Thomas Hellström wrote: > Hi, > > On Mon, 2025-09-01 at 20:16 +0200, Maarten Lankhorst wrote: >> Hello David, >> >> Den 2025-09-01 kl. 14:25, skrev David Hildenbrand: >>> On 19.08.25 13:49, Maarten Lankhorst wrote: >>>> When exporting dma-bufs to other devices, even when it is allowed >>>> to use >>>> move_notify in some drivers, performance will degrade severely >>>> when >>>> eviction happens. >>>> >>>> A perticular example where this can happen is in a multi-card >>>> setup, >>>> where PCI-E peer-to-peer is used to prevent using access to >>>> system memory. >>>> >>>> If the buffer is evicted to system memory, not only the evicting >>>> GPU wher >>>> the buffer resided is affected, but it will also stall the GPU >>>> that is >>>> waiting on the buffer. >>>> >>>> It also makes sense for long running jobs not to be preempted by >>>> having >>>> its buffers evicted, so it will make sense to have the ability to >>>> pin >>>> from system memory too. >>>> >>>> This is dependant on patches by Dave Airlie, so it's not part of >>>> this >>>> series yet. But I'm planning on extending pinning to the memory >>>> cgroup >>>> controller in the future to handle this case. >>>> >>>> Implementation details: >>>> >>>> For each cgroup up until the root cgroup, the 'min' limit is >>>> checked >>>> against currently effectively pinned value. If the value will go >>>> above >>>> 'min', the pinning attempt is rejected. >>>> >>>> Pinned memory is handled slightly different and affects >>>> calculating >>>> effective min/low values. Pinned memory is subtracted from both, >>>> and needs to be added afterwards when calculating. >>> >>> The term "pinning" is overloaded, and frequently we refer to >>> pin_user_pages() and friends. >>> >>> So I'm wondering if there is an alternative term to describe what >>> you want to achieve. >>> >>> Is it something like "unevictable" ? >> It could be required to include a call pin_user_pages(), in case a We'll only care about long-term pinnings (i.e., FOLL_LONGTERM). Ordinary short-term pinning is just fine. (see how even "pinning" is overloaded? :) ) >> process wants to pin >> from a user's address space to the gpu. >> >> It's not done yet, but it wouldn't surprise me if we want to include >> it in the future. >> Functionally it's similar to mlock() and related functions. Traditionally, vfio, io_uring and rdma do exactly that: they use GUP to longterm pin and then account that memory towards RLIMIT_MEMLOCK. If you grep for "rlimit(RLIMIT_MEMLOCK)", you'll see what I mean. There are known issues with that: imagine long-term pinning the same folio through GUP with 2 interfaces (e.g., vfio, io_uring, rdma), or within the same interface. You'd account the memory multiple times, which is horrible. And so far there is no easy way out. >> >> Perhaps call it mlocked instead? > > I was under the impression that mlocked() memory can be migrated to > other physical memory but not to swap? whereas pinned memory needs to > remain the exact same physical memory. Yes, exactly. > > IMO "pinned" is pretty established within GPU drivers (dma-buf, TTM) > and essentially means the same as "pin" in "pin_user_pages", so > inventing a new name would probably cause even more confusion? If it's the same thing, absolutely. But Marteen said "It's not done yet, but it wouldn't surprise me if we want to include it in the future". So how is the memory we are talking about in this series "pinned" ? -- Cheers David / dhildenb