Re: [PATCH v1 1/3] mm: memcg: deprecate the non-hierarchical mode

[Johannes Weiner]

On Tue, Nov 10, 2020 at 02:07:58PM -0800, Roman Gushchin wrote:
> The non-hierarchical cgroup v1 mode is a legacy of early days
> of the memory controller and doesn't bring any value today.
> However, it complicates the code and creates many edge cases
> all over the memory controller code.
> 
> It's a good time to deprecate it completely.
> 
> Functionally this patch enabled is by default for all cgroups
> and forbids switching it off. Nothing changes if cgroup v2 is used:
> hierarchical mode was enforced from scratch.
> 
> To protect the ABI memory.use_hierarchy interface is preserved
> with a limited functionality: reading always returns "1", writing
> of "1" passes silently, writing of any other value fails with
> -EINVAL and a warning to dmesg (on the first occasion).
> 
> Signed-off-by: Roman Gushchin <guro@xxxxxx>
> Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
> Acked-by: David Rientjes <rientjes@xxxxxxxxxx>

...and don't let the door hit you on the way out ;-)

Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>