Re: [RFC PATCH rdma-next 0/5] cgroup/rdma: add per-type resource accounting for QP, MR and MR memory

[Jason Gunthorpe <jgg@ziepe.ca>]

On Thu, May 28, 2026 at 03:55:37PM +0800, Tao Cui wrote:
> Hi,Jason
> 
> > memory pin accounting should ideally be limited by the cgroup directly
> > but we argued about that for a while and could never get an agreement
> > of an acceptable implementation. There are many nasty corner cases
> > around cgroups and fork and other cases IIRC
> >
> > So I'm not sure if making it rdma specific can easially solve these
> > problems
> 
> Thanks for the detailed context.  I understand the concern — generic
> pinned-page accounting at the memcg level has difficult ownership
> semantics around fork(), cgroup migration, shared mappings, and page
> lifetime tracking.
> 
> The intent of mr_mem is narrower and RDMA-scoped.  It is not page-level
> ownership tracking — it is object-based accounting tied to the MR
> lifetime:
> 
>   - charged at MR registration time
>   - uncharged at MR destruction time
>   - the charge lives with the MR's creating cgroup for the entire
>     lifetime of the MR object

Okay, that's an interesting framing. Perhaps it can work, you should
include this in the commit message and be sure to CC the cgroup
people.

Jason