Hello,

On Thu, Feb 13, 2020 at 05:36:36PM +0100, Michal Hocko wrote:

AFAIK systemd already offers knobs to configure resource controls [1].

Yes, it can set up the control knobs as directed but it doesn't ship
with any material resource configurations or has conventions set up
around it.

Besides that we are talking about memcg features which are available only
unified hieararchy and that is what systemd is using already.

I'm not quite sure what the above sentence is trying to say.

quoted

You gotta
change the layout to configure resource control no matter what and
it's pretty easy to do. systemd folks are planning to integrate higher
level resource control features, so my expectation is that the default
layout is gonna change as it develops.

Do you have any pointers to those discussions? I am not really following
systemd development.

There's a plan to integrate streamlined implementation of oomd into
systemd. There was a thread somewhere but the only thing I can find
now is a phoronix link.

  https://www.phoronix.com/scan.php?page=news_item&px=Systemd-Facebook-OOMD

systemd recently implemented DisableControllers so that upper level
slices can have authority over what controllers are enabled below it
and in a similar vein there were discussions over making it
auto-propagate some of the configs down the hierarchy but kernel doing
the right thing and maintaining consistent semantics across
controllers seems to be the right approach.

There was also a discussion with a distro. Nothing concrete yet but I
think we're more likely to see more resource control configs being
deployed by default in the future.

Anyway, I am skeptical that systemd can do anything much more clever
than placing cgroups with a resource control under the root cgroup. At
least not without some tagging which workloads are somehow related.

Yeah, exactly, all it needs to do is placing scopes / services
according to resource hierarchy and configure overall policy at higher
level slices, which is exactly what the memory.low semantics change
will allow.

That being said, I do not really blame systemd here. We are not making
their life particularly easy TBH.

Do you mind elaborating a bit?

Thanks.

-- 
tejun