[systemd-devel] How does hybrid cgroup setup work?

[Lennart Poettering]

On So, 12.11.17 20:17, Umut Tezduyar Lindskog (umut at tezduyar.com) wrote:

> > And then there's also the big issue: the cgroup code is complex enough
> > given that we need to support three different setups. I'd really
> > prefer if we'd not add even more to that. In fact, I am really looking
> > forward for the day we can drop all cgroup support besides the unified
> > one from our tree. We could delete *so much* code then! And there's
> > only one thing hackers prefer over writing code: deleting code... ;-)
> 
> I guess that day will come when all the controllers move to v2. What
> is your knowledge regarding plans of moving all the control groups?
> Are they all going to be moved? If so, are they all going to provide
> somehow similar functionality? For example I have noticed I cannot
> find a similar functionality of "memory.max_usage_in_bytes" in v2
> memory control group. I am not sure if everyone will be happily jump
> to #2 (unified) way any time soon or if they will still want to use
> some parts from v1 in an unified fashion meanwhile.

As I understood Tejun the major controllers will all be moved, but
some some will be dropped entirely, for example the "devices" one
(since what it does is not precisely resource management but access
management, and it is mostly redundant as seccomp + picking carefully
how /dev is put together has the same effect.

the memory controller should be fully moved over already. systemd's
MemoryMax= should do the right thing already.

Lennart

-- 
Lennart Poettering, Red Hat