RFR: 8239559: Cgroups: Incorrect detection logic on some systems

[Baesken, Matthias]

Hi Severin, makes sense !

Maybe  you could adjust the comment and add a bit of info about this .

I do not need to see a new webrev .


Best regards, Matthias

> 
> What you are seeing here is a hybrid system[1]. My workstation is
> hybrid as well. Legacy and hybrid systems are being detected as cgroup
> v1. A hybrid systems mostly behaves like a cgroup v1 system. All the
> controllers are mounted via cgroup v1. If if was detected as cgroup v2
> (unified) most of the imposed memory/cpu limits wouldn't be accounted
> for.
> 
> >
> > But the comment    in
> >
> > http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-
> 8239559/02/webrev/src/java.base/linux/classes/jdk/internal/platform/Cgro
> upSubsystemFactory.java.frames.html
> >
> >
> > says
> >
> >  102         // For cgroups v2 all controllers need to have zero hierarchy id
> >  103         // and /proc/self/mountinfo needs to have at least one cgroup
> filesystem
> >  104         // mounted.
> >
> >
> > Should this comment be adjusted ?
> > On the system above  we  have no 0  in  /proc/cgroups   however  it seems
> to me the system supports  cgroug v2 ?
> 
> The comment is still correct. There is a difference between a true
> cgroup v2 only system and a hybrid system like the one you are seing.
> We should only detect true cgroup v2 systems as such.
> 
> Does that make sense?
>