Re: [RFC PATCH 0/3] Cgroup-based THP control

[Michal Hocko <mhocko@suse.com>]

On Wed 30-10-24 16:33:08, gutierrez.asier@huawei-partners.com wrote:
> From: Asier Gutierrez <gutierrez.asier@huawei-partners.com>
> 
> Currently THP modes are set globally. It can be an overkill if only some
> specific app/set of apps need to get benefits from THP usage. Moreover, various
> apps might need different THP settings. Here we propose a cgroup-based THP
> control mechanism.
> 
> THP interface is added to memory cgroup subsystem. Existing global THP control
> semantics is supported for backward compatibility. When THP modes are set
> globally all the changes are propagated to memory cgroups. However, when a
> particular cgroup changes its THP policy, the global THP policy in sysfs remains
> the same.

Do you have any specific examples where this would be benefitial?

> New memcg files are exposed: memory.thp_enabled and memory.thp_defrag, which
> have completely the same format as global THP enabled/defrag.
> 
> Child cgroups inherit THP settings from parent cgroup upon creation. Particular
> cgroup mode changes aren't propagated to child cgroups.

So this breaks hierarchical property, doesn't it? In other words if a
parent cgroup would like to enforce a certain policy to all descendants
then this is not really possible. 
-- 
Michal Hocko
SUSE Labs