Re: [PATCH bpf-next 0/5] bpf, mm: introduce cgroup.memory=nobpf

[Johannes Weiner <hannes@cmpxchg.org>]

On Sun, Feb 05, 2023 at 06:58:00AM +0000, Yafang Shao wrote:
> The bpf memory accouting has some known problems in contianer
> environment,
> 
> - The container memory usage is not consistent if there's pinned bpf
>   program
>   After the container restart, the leftover bpf programs won't account
>   to the new generation, so the memory usage of the container is not
>   consistent. This issue can be resolved by introducing selectable
>   memcg, but we don't have an agreement on the solution yet. See also
>   the discussions at https://lwn.net/Articles/905150/ .
> 
> - The leftover non-preallocated bpf map can't be limited
>   The leftover bpf map will be reparented, and thus it will be limited by 
>   the parent, rather than the container itself. Furthermore, if the
>   parent is destroyed, it be will limited by its parent's parent, and so
>   on. It can also be resolved by introducing selectable memcg.
> 
> - The memory dynamically allocated in bpf prog is charged into root memcg
>   only
>   Nowdays the bpf prog can dynamically allocate memory, for example via
>   bpf_obj_new(), but it only allocate from the global bpf_mem_alloc
>   pool, so it will charge into root memcg only. That needs to be
>   addressed by a new proposal.
> 
> So let's give the user an option to disable bpf memory accouting.
> 
> The idea of "cgroup.memory=nobpf" is originally by Tejun[1].

I'm not the most familiar with bpf internals, but the memcg bits and
adding the boot time flag look good to me:

Acked-by: Johannes Weiner <hannes@cmpxchg.org>