On Tue, Aug 25, 2026 at 06:26:42PM +0200, Michal Hocko wrote: > On Tue 25-08-26 17:45:56, David Hildenbrand wrote: > > On 8/25/26 16:47, Eric Chanudet wrote: > > > On Mon, Aug 24, 2026 at 10:58:18AM +0200, Michal Hocko wrote: > > >> On Fri 21-08-26 14:56:52, Eric Chanudet wrote: > > >>> CMA allocations are currently unaccounted for by cgroup memory > > >>> controllers. As system resources, they should fall under memcg, but CMA > > >>> areas partition the available space for different purposes and memcg > > >>> doesn't have a good representation for that. > > >> > > >> Which CMA usecases are covered by this work? It would be also great to > > >> spend more time describing usecases. > > > > > > We would like to offer some usage guaranties to userspace processes > > > ending up doing allocations in CMA. > > > > How does this e.g., relate to hugetlb allocating from CMA, to then charge > > to a > > hugetlb cgroup? > >
AFAIU the system defines CMA areas to allocate hugepages from. For this initial series, I failed to handle it. The intend was to consider it as any other CMA area. It entirely missed that hugepages are already accounted for by their controller (cgroupfs opt memory_hugetlb_accounting) and they are charged when faulted in from their available pool. > > I always thought of CMA being a low-level allocation mechanism with various > > different use cases, and actually the higher-level users should decide how > > to/what to charge instead. > > Exactly. There are many different users of CMA all with different > requirements. Then there is CMA reservations if an area is shared and > the overall memory consumption. That is why I am really not able to > wrap my head around this proposal. It is nonetheless available almost directly to userspace via dmabuf heap, or as a result of drivers ioctl providing a contiguous buffer, and unaccounted for by existing controllers, with the exception of CMA hugepages with memory_hugetlb_accounting. The dmabuf heap use would have userspace choose the area(s), but allow for no limit to be applied beyond that, which is desirable for areas shared by multiple userspace components. > > > -- > Michal Hocko > SUSE Labs > -- Eric Chanudet
