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[2003:d8:2f0a:ca00:f74f:2017:1617:3ec3]) by smtp.gmail.com with ESMTPSA id o16-20020a05600c379000b003dc49e0132asm10585172wmr.1.2023.01.31.06.15.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 31 Jan 2023 06:15:50 -0800 (PST) Message-ID: <1a2417bc-f3ac-3e63-a930-bdefaab2578e@redhat.com> Date: Tue, 31 Jan 2023 15:15:49 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 Subject: Re: [RFC PATCH 00/19] mm: Introduce a cgroup to limit the amount of locked and pinned memory To: Jason Gunthorpe Cc: Alistair Popple , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, jhubbard@nvidia.com, tjmercier@google.com, hannes@cmpxchg.org, surenb@google.com, mkoutny@suse.com, daniel@ffwll.ch References: <6369225e-3522-341b-cd20-d95b1f11ea71@redhat.com> <2e78d261-9ae9-d203-446e-eaa3c652ca6e@redhat.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: ppdy9yx87e8r7izbjq5hg5ti8o6jar5g X-Rspam-User: X-Rspamd-Queue-Id: 5797040029 X-Rspamd-Server: rspam06 X-HE-Tag: 1675174554-451689 X-HE-Meta: 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 3UUIa0L4 4dIj/PvbDpopK4kaUt1kEwJBrCZkSqg3izZeuxd/7QbTa0k1aVWqBzaQjK2+kLnJ/V/Bvpqgz0wPeYEtHiNwgQPy4ZIMAyX6+mOAoaQHkUIVH5veq/2yEfzQ9r0MUWOoaGKEDqMDnyu3h/ak31zp9FzWiNn5KNpdutH6RWusYtfh+jAO8wh3mZtOrE3iN4lftuY6jflHkK7+fsWZHvIrqbcwZKKs775pL6zRxkb8cY0sqh0IZfHInAMv6x+ZCZHFK8gC2MQOpnTzIoPqKKkQti9lU16iaSemTsRPvHBjTKYFxq0pnZiS0ag5t+pKqNPJgPTh2QqRiEZrTp3BNvCGDoi2LKrrBRKOnwd+I/7q9XXF020WUZGb3xpZIN39ro3hU0117U5Llt1ZAnZjZAtXhJpwvn5ZG0UkaXLT8YKm2Qe/gnu4FxfhXNRJzxSqGQ8GgX+jI+5mIp5pv8slTgu1/iDlEZQ== 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: On 31.01.23 15:10, Jason Gunthorpe wrote: > On Tue, Jan 31, 2023 at 03:06:10PM +0100, David Hildenbrand wrote: >> On 31.01.23 15:03, Jason Gunthorpe wrote: >>> On Tue, Jan 31, 2023 at 02:57:20PM +0100, David Hildenbrand wrote: >>> >>>>> I'm excited by this series, thanks for making it. >>>>> >>>>> The pin accounting has been a long standing problem and cgroups will >>>>> really help! >>>> >>>> Indeed. I'm curious how GUP-fast, pinning the same page multiple times, and >>>> pinning subpages of larger folios are handled :) >>> >>> The same as today. The pinning is done based on the result from GUP, >>> and we charge every returned struct page. >>> >>> So duplicates are counted multiple times, folios are ignored. >>> >>> Removing duplicate charges would be costly, it would require storage >>> to keep track of how many times individual pages have been charged to >>> each cgroup (eg an xarray indexed by PFN of integers in each cgroup). >>> >>> It doesn't seem worth the cost, IMHO. >>> >>> We've made alot of investment now with iommufd to remove the most >>> annoying sources of duplicated pins so it is much less of a problem in >>> the qemu context at least. >> >> Wasn't there the discussion regarding using vfio+io_uring+rdma+$whatever on >> a VM and requiring multiple times the VM size as memlock limit? > > Yes, but iommufd gives us some more options to mitigate this. > > eg it makes some of logical sense to point RDMA at the iommufd page > table that is already pinned when trying to DMA from guest memory, in > this case it could ride on the existing pin. Right, I suspect some issue is that the address space layout for the RDMA device might be completely different. But I'm no expert on IOMMUs at all :) I do understand that at least multiple VFIO containers could benefit by only pinning once (IIUC that mgiht have been an issue?). > >> Would it be the same now, just that we need multiple times the pin >> limit? > > Yes Okay, thanks. It's all still a big improvement, because I also asked for TDX restrictedmem to be accounted somehow as unmovable. -- Thanks, David / dhildenb