On Fri 14-02-20 08:57:28, Tejun Heo wrote:
[...]

Sorry to skip over a large part of your response. The discussion in this
thread got quite fragmented already and I would really like to conclude
to something.

quoted

I believe I have already expressed the configurability concern elsewhere
in the email thread. It boils down to necessity to propagate
protection all the way up the hierarchy properly if you really need to
protect leaf cgroups that are organized without a resource control in
mind. Which is what systemd does.

But that doesn't work for other controllers at all. I'm having a
difficult time imagining how making this one control mechanism work
that way makes sense. Memory protection has to be configured together
with IO protection to be actually effective.

Please be more specific. If the protected workload is mostly in-memory,
I do not really see how IO controller is relevant. See the example of
the DB setup I've mentioned elsewhere.

As for cgroup hierarchy being unrelated to how controllers behave, it
frankly reminds me of cgroup1 memcg flat hierarchy thing I'm not sure
how that would actually work in terms of resource isolation. Also, I'm
not sure how systemd forces such configurations and I'd think systemd
folks would be happy to fix them if there are such problems. Is the
point you're trying to make "because of systemd, we have to contort
how memory controller behaves"?

No, I am just saying and as explained in reply to Johannes, there are
practical cases where the cgroup hierarchy reflects organizational
structure as well.
-- 
Michal Hocko
SUSE Labs