Re: [ckrm-tech] [RFC 3/5] sched: Add CPU rate hard caps

[Balbir Singh <balbir@in.ibm.com>]

Peter Williams wrote:
<snip>

> > > But you don't need something as complex as CKRM either.  This capping
> >
> > All CKRM^W Resource Groups does is to group unrelated/related tasks to a
> > group and apply resource limits. 
> >
> >
> > > functionality coupled with (the lamented) PAGG patches (should have been 
> > > called TAGG for "task aggregation" instead of PAGG for "process 
> > > aggregation") would allow you to implement a kernel module that could 
> > > apply caps to arbitrary groups of tasks.
> >
> > I do not follow how PAGG + this cap feature can be used to put cap of
> > related/unrelated tasks. Can you provide little more explanation,
> > please.
>
>
> I would have thought it was fairly obvious.  PAGG supplies the task 
> aggregation mechanism, these patches provide per task caps and all 
> that's needed is the code that marries the two.

The problem is that with per-task caps, if I have a resource group A
and I want to limit it to 10%, I need to limit each task in resource
group A to 10% (which makes resource groups not so useful). Is my
understanding correct? Is there a way to distribute the group limit
across tasks in the resource group?

> > Also, i do not think it can provide guarantees to that group of tasks.
> > can it ?
>
>
> It could do that by manipulating nice which is already available in the 
> kernel.
>
> I.e. these patches plus improved statistics (which are coming, I hope) 
> together with the existing policy controls provide all that is necessary 
> to do comprehensive CPU resource control.  If there is an efficient way 
> to get the statistics out to user space (also coming, I hope) this 
> control could be exercised from user space.

Could you please provide me with a link to the new improved statistics.
What do the new statistics contain - any heads up on them?

> Peter


--

	Balbir Singh,
	Linux Technology Center,
	IBM Software Labs
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