Cgroups RT scheduling
a.p.zijlstra at chello.nl
Fri Sep 11 04:47:20 PDT 2009
On Fri, 2009-09-11 at 16:53 +0530, Dhaval Giani wrote:
> [Adding peterz to the cc]
> On Wed, Sep 09, 2009 at 04:49:52PM +0100, Rolando Martins wrote:
> > Hi,
> > I would like to confirm the following:
> > cpuset.sched_load_balance doesn't work with RT, right?
> > You cannot have tasks for sub-domain 2 to utilize bandwidth of
> > sub-domain 3, right?
Depends on what you do, for some contorted reason we have 2 cpu control
groups, cpusets and this other thing.
I'm still wanting to fold them into one, this confusion is in part
because of that train-wreck.
You can place a task in one cpuset cgroup and in another scheduler
cgroup - but yeah, that does interact funny with the load-balancer.
> > __1__
> > / \
> > 2 3
> > (50% rt) (50% rt )
> > For my application domain;) it would be interesting to have
> > rt_runtime_ns as a min. of allocated rt and not a max.
> > Ex. If an application of domain 2 needs to go up to 100% and domain 3
> > is idle, then it would be cool to let it utilize the full bandwidth.
> > (we also could have a hard upper limit in each sub-domain, like
> > hard_up=0.8, i.e. even if we could get 100%, we will only utilize
> > 80%).
This doesn't sound a like a real-time application.
Variable bandwidth is useless for determinism.
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