Re: [PATCH v3 01/14] sched/core: uclamp: extend sched_setattr to support utilization clamping

Quentin Perret
2018-08-17T10:34:48Z

Hi Patrick,

On Thursday 09 Aug 2018 at 16:23:13 (+0100), Patrick Bellasi wrote:
> On 09-Aug 11:50, Juri Lelli wrote:
> > On 09/08/18 10:14, Patrick Bellasi wrote:
> > > On 07-Aug 14:35, Juri Lelli wrote:
> > > > On 06/08/18 17:39, Patrick Bellasi wrote:
>
> [...]
>
> > > 1) make CAP_SYS_NICE protected the clamp groups, with an optional boot
> > > time parameter to relax this check
> >
> > It seems to me that this might work well with that the intended usage of
> > the interface that you depict above. SMS only (or any privileged user)
> > will be in control of how groups are configured, so no problem for
> > normal users.
>
> Yes, well... apart normal users still getting a -ENOSPC is they are
> requesting one of the not pre-configured clamp values. Which is why
> the following bits can be helpful.

So IIUC, normal users would still be free of choosing their clamp values
as long as they choose one in the list of pre-allocated ones ? Is that
correct ?

If yes, that would still let normal users make they tasks look bigger no ?
They could just choose the clamp group with the highest min_clamp or
something. Isn't this a problem too ? I mean, if that can be abused easily,
I'm pretty sure people _will_ abuse it ...

Or maybe I misunderstood something ?

Thanks,
Quentin