Re: [PATCH 14/19] mm: Introduce a cgroup for pinned memory

[Tejun Heo]

Hello,

On Mon, Feb 06, 2023 at 07:40:55PM -0400, Jason Gunthorpe wrote:
> (a) kind of destroys the point of this as a sandboxing tool
> 
> It is not so harmful to use memory that someone else has been charged
> with allocating.
> 
> But it is harmful to pin memory if someone else is charged for the
> pin. It means it is unpredictable how much memory a sandbox can
> actually lock down.
> 
> Plus we have the double accounting problem, if 1000 processes in
> different cgroups open the tmpfs and all pin the memory then cgroup A
> will be charged 1000x for the memory and hit its limit, possibly
> creating a DOS from less priv to more priv

Let's hear what memcg people think about it. I'm not a fan of disassociating
the ownership and locker of the same page but it is true that actively
increasing locked consumption on a remote cgroup is awkward too.

Thanks.

-- 
tejun