Re: [PATCH v10 7/8] cgroup/cpuset: Update description of cpuset.cpus.partition in cgroup-v2.rst

[Waiman Long]

On 5/4/22 07:25, Michal Koutný wrote:
> Hello.
>
> On Tue, May 03, 2022 at 12:21:48PM -0400, Waiman Long <longman@xxxxxxxxxx> wrote:
> >   Documentation/admin-guide/cgroup-v2.rst | 145 +++++++++++++-----------
> >   1 file changed, 79 insertions(+), 66 deletions(-)
> A note across various lines -- it seems your new text accidentally mixes
> both spaces and tabs for indentation.

You are right. I will fix that.

> > diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
> > index 69d7a6983f78..94e1e3771830 100644
> > --- a/Documentation/admin-guide/cgroup-v2.rst
> > +++ b/Documentation/admin-guide/cgroup-v2.rst
> > [...]
> > +	The value shown in "cpuset.cpus.effective" of a partition root is
> > +	the CPUs that the parent partition root can dedicate to the new
> > +	partition root.  They are subtracted from "cpuset.cpus.effective"
> > +	of the parent and may be different from "cpuset.cpus"
> I find this paragraph a bit hard to comprehend (I read it as it talks
> about three levels of cgroups (parent, child, grandparent). It is
> correct but I'd suggect following formulation (where I additionally
> simplifed it by talking about "available" cpus):
>
> > The value shown in "cpuset.cpus.effective" of a partition root is
> > the CPUs that the partition root can dedicate to a potential new child
> > partition root. The new child subtracts available CPUs from its parent
> > "cpuset.cpus.effective".


Thanks for the suggestion, will modify the text as suggested.


> > +	For a partition root to become valid, the following conditions
> > +	must be met.
> > +
> > +	1) The "cpuset.cpus" is exclusive, i.e. they are not shared by
> > +	   any of its siblings (exclusivity rule).
> > +	2) The parent cgroup is a valid partition root.
> > +	3) The "cpuset.cpus" is not empty and must contain at least
> > +	   one of the CPUs from parent's "cpuset.cpus", i.e. they overlap.
> > +        4) The "cpuset.cpus.effective" must be a subset of "cpuset.cpus"
> > +           and cannot be empty unless there is no task associated with
> > +           this partition.
> This sounds good to me.
>
> > +        Care must be taken to change a valid partition root to "member"
> > +        as all its child partitions, if present, will become invalid.
> This does not talk about recovering. Is it intentional? (I.e. to left
> implementation defined)

This new patch series does have the ability to recover now.  I am just 
not emphasizing the recovery aspect of it in the doc file. I will add a 
sentence about it.

> Except the remarks above, I find the concepts described here good. I'll
> reply to implementation separately & later.

Thanks,
Longman