Re: [RFC 0/5] forced comounts for cgroups.

Glauber Costa
2012-09-05T08:58:43Z

On 09/05/2012 12:47 PM, Tejun Heo wrote:
> Hello, Glauber.
>
> On Wed, Sep 05, 2012 at 12:35:11PM +0400, Glauber Costa wrote:
>>> As long as cpuacct and cpu are separate, I think it makes sense to
>>> assume that they at least could be at different granularity.
>>
>> If they are comounted, and more: forceably comounted, I don't see how to
>> call them separate. At the very best, they are this way for
>> compatibility purposes only, to lay a path that would allow us to get
>> rid of the separation eventually.
>
> I think this is where we disagree. I didn't mean that all controllers
> should be using exactly the same hierarchy when I was talking about
> unified hierarchy. I do think it's useful and maybe even essential to
> allow differing levels of granularity. cpu and cpuacct could be a
> valid example for this. Likely blkcg and memcg too.
>
> So, I think it's desirable for all controllers to be able to handle
> hierarchies the same way and to have the ability to tag something as
> belonging to certain group in the hierarchy for all controllers but I
> don't think it's desirable or feasible to require all of them to
> follow exactly the same grouping at all levels.
>

By "different levels of granularity" do you mean having just a subset of
them turned on at a particular place?

If yes, having them guaranteed to be comounted is still perceived by me
as a good first step. A natural following would be to turn them on/off
on a per-group basis.