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[91.12.103.101]) by smtp.gmail.com with ESMTPSA id 38sm13027369wrc.1.2021.11.23.09.04.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 23 Nov 2021 09:04:18 -0800 (PST) Message-ID: <98470479-7ba9-9f05-e597-e5afeb3464a3@redhat.com> Date: Tue, 23 Nov 2021 18:04:16 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: [PATCH] Increase default MLOCK_LIMIT to 8 MiB Content-Language: en-US To: Jason Gunthorpe Cc: Jens Axboe , Andrew Dona-Couch , Andrew Morton , Drew DeVault , Ammar Faizi , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, io_uring Mailing List , Pavel Begunkov , linux-mm@kvack.org References: <20211116133750.0f625f73a1e4843daf13b8f7@linux-foundation.org> <8f219a64-a39f-45f0-a7ad-708a33888a3b@www.fastmail.com> <333cb52b-5b02-648e-af7a-090e23261801@redhat.com> <5f998bb7-7b5d-9253-2337-b1d9ea59c796@redhat.com> <20211123132523.GA5112@ziepe.ca> <10ccf01b-f13a-d626-beba-cbee70770cf1@redhat.com> <20211123140709.GB5112@ziepe.ca> <20211123170056.GC5112@ziepe.ca> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20211123170056.GC5112@ziepe.ca> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 23.11.21 18:00, Jason Gunthorpe wrote: > On Tue, Nov 23, 2021 at 03:44:03PM +0100, David Hildenbrand wrote: >> On 23.11.21 15:07, Jason Gunthorpe wrote: >>> On Tue, Nov 23, 2021 at 02:39:19PM +0100, David Hildenbrand wrote: >>>>> >>>>>> 2) Could be provide a mmu variant to ordinary users that's just good >>>>>> enough but maybe not as fast as what we have today? And limit >>>>>> FOLL_LONGTERM to special, privileged users? >>>>> >>>>> rdma has never been privileged >>>> >>>> Feel free to correct me if I'm wrong: it requires special networking >>>> hardware and the admin/kernel has to prepare the system in a way such >>>> that it can be used. >>> >>> Not really, plug in the right PCI card and it works >> >> Naive me would have assumed that the right modules have to be loaded >> (and not blacklisted), that there has to be an rdma service installed >> and running, that the NIC has to be configured in some way, and that >> there is some kind of access control which user can actually use which >> NIC. > > Not really, we've worked hard that it works as well as any other HW > device. Plug it in and it works. > > There is no systemd service, or special mandatory configuration, for > instance. > >> For example, I would have assume from inside a container it usually >> wouldn't just work. > > Nope, RDMA follows the net namespaces of its ethernet port, so it just > works in containers too. > >> believe what you say and I trust your experience :) So could as well be >> that on such a "special" (or not so special) systems there should be a >> way to restrict it to privileged users only. > > At this point RDMA is about as "special" as people running large > ZONE_MOVABLE systems, and the two are going to start colliding > heavily. The RDMA VFIO migration driver should be merged soon which > makes VMs using this stuff finally practical. Sounds like fun. At least we documented it already ;) https://www.kernel.org/doc/html/latest/admin-guide/mm/memory-hotplug.html#zone-movable-sizing-considerations -- Thanks, David / dhildenb