Re: [PATCH 00/10] cgroups: Task counter subsystem v6

[Glauber Costa <glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>]

On 11/03/2011 03:28 PM, Paul Menage wrote:
> On Thu, Nov 3, 2011 at 10:06 AM, Glauber Costa<glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>  wrote:
>> Sorry if I wasn't clear: It removes the need to walk multiple independent
>> hierarchies. The walk is done only once.
>
> You're talking about at fork time, and the concern is the cache
> footprint involved in walking up the parent pointer chain?

Yes, we can say this is my main concern.

> Isn't that an argument against multiple hierarchies (which is a
> decision for the admin), rather than against more subsystem
> flexibility?

Not always it is a decision for the admin. In most cases, it is a 
constraint of the problem. For containers - take lxc as an example,
the most reasonable thing to do is to grab all cgroups subsystems 
available, and contain them.

> If multiple subsystems on the same hierarchy each need to
> walk up the pointer chain on the same event, then after the first
> subsystem has done so the chain will be in cache for any subsequent
> walks from other subsystems.
No, it won't. Precisely because different subsystems have completely
independent pointer chains.