Messages in this thread | | | Date | Tue, 31 Jan 2023 15:06:10 +0100 | Subject | Re: [RFC PATCH 00/19] mm: Introduce a cgroup to limit the amount of locked and pinned memory | From | David Hildenbrand <> |
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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? Would it be the same now, just that we need multiple times the pin limit?
-- Thanks,
David / dhildenb
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