Re: [PATCH v5 13/16] mm: memcontrol: reuse memory cgroup ID for kmem ID

[Michal Koutný]

On Mon, Dec 20, 2021 at 04:56:46PM +0800, Muchun Song <songmuchun@xxxxxxxxxxxxx> wrote:
> There are two idrs being used by memory cgroup, one is for kmem ID,
> another is for memory cgroup ID. The maximum ID of both is 64Ki.
> Both of them can limit the total number of memory cgroups.
> Actually, we can reuse memory cgroup ID for kmem ID to simplify the
> code.

An interesting improvement.

I'm a bit dense -- what's the purpose the MEM_CGROUP_ID_DIFF offset?
Couldn't this deduplication be extended to only use mem_cgroup.id.id
instead of mem_cgroup.kmemcg_id? (With a boolean telling whether kmem
accounting is active.)

Thanks,
Michal