[Devel] Re: [RFC | PATCH 0/9] CPU controller over process container

[Srivatsa Vaddagiri]

On Thu, Apr 12, 2007 at 07:56:47PM +0200, Herbert Poetzl wrote:
> >         - Each task-group gets its own runqueue on every cpu.
> 
> how does that scale for, let's say 200-300 guests on a
> 'typical' dual CPU machine?

Scheduling complexity is still O(1) and hence I would say CPU-wise, it
should be very scalable. Memory-wise, I agree that this can consume more
memory if number of guests are large ..But this I feel is a memory vs
cpu tradeoff ..If you had only one queue in which tasks from all groups
were present, then it increases the schedule() complexity ?

If there are specific tests you had in mind to test this scalability
aspect, I would be happy to run them.

> >         - In addition, there is an active and expired array of
> >           task-groups themselves. Task-groups that have expired their
> >           quota are put into expired array.
> 
> how much overhead does that add to the scheduler, cpu
> and memory wise?

cpu-wise, it should add very little overhead (since O(1) behavior is
retained). memory-wise, same points as above.

> >         - Scheduling the next task involves picking highest priority task-group
> >           from active array first and then picking highest-priority task
> >           within it. Both steps are O(1).
> 
> how does that affect interactivity?

Note that I define task-group priority = highest priority tasks the
group has, which IMO should give decent if not good interactivity ..But is
(good) interactivity a big requirement here? As we know, that's a hard
thing to achieve even in today's O(1) scheduler ..

> >         - SMP load-balancing is accomplished on the lines of smpnice.
> 
> what about strict CPU limits (i.e. 20% regardless of
> the idle state of the machine)

Not supported in these patches. Any idea how/where that would be
usefull?

-- 
Regards,
vatsa
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