Re: [ckrm-tech] [RFC] Resource Management - Infrastructure choices

[Pavel Emelianov <xemul@openvz.org>]

>> I believe this can be done, but can't imagine how to use this...
> 
> As I mentioned in my earlier mail, I thought openvz folks did want this
> flexibility:
> 
> 	http://lkml.org/lkml/2006/8/18/98
> 
> Also:
> 
> 	http://lwn.net/Articles/94573/
> 
> But I am ok if we dont support this feature in the initial round of
> development.

Yes. Lets start with it - no separate groupings for a while.

BTW I think that hierarchy is a good (and easier to make than)
replacement for separate grouping. Say if I want two groups to
have separate CPU shares and common kmemsize this is the same as
if I want one group for kmemsize with two kids - one for X% of
CPU share and the other for Y%. And this (hierarchy) provides
more flexibility than "plain" although separate grouping.
Moreover configfs can provide a clean interface for it. E.g.
 $ mkdir /configfs/beancounters/0
 $ mkdir /configfs/beancounters/0/1
 $ mkdir /confgifs/beancounters/0/2
and each task_struct will have a single pointer - current
container - but not 10 - for each controller.

What do you think?

> Having grouping for different resources could be a hairy to deal
> with and could easily mess up applications (for ex: a process in a 80%

That's it... One more thing against separate grouping.

[snip]

> Isnt /proc/<pid> listed also in /proc/<pid>/task/<tid>?
> 
> For ex:
> 
> 	# ls /proc/2906/task
> 	2906  2907  2908  2909
> 
> 2906 is the main thread which created the remaining threads.
> 
> This would lead to an ambiguity when user does something like below:
> 
> 	echo 2906 > /some_res_file_system/some_new_group
> 
> Is he intending to move just the main thread, 2906, to the new group or
> all the threads? It could be either.
> 
> This needs some more thought ...

I agree with Paul Menage that having
/configfs/beancounters/<id>/tasks and /.../threads is perfect.