Re: [PATCH 3/5] uclampset: Add man page

[Vincent Guittot <vincent.guittot@linaro.org>]

On Sat, 23 Jan 2021 at 19:31, Qais Yousef <qais.yousef@arm.com> wrote:
>
> On 01/20/21 15:46, Vincent Guittot wrote:
> > > +.TP
> > > +For example:
> > > +.B uclampset \-s
> > > +.I -m\ 512
> > > +.I -M\ 700
> > > +.PP
> > > +will prevent any task from being boosted higher than 512. And all tasks in the
> >
> > will prevent any task from being boosted higher than 700
>
> 700 or 512 you mean here?
>
> > or
> > will ensure  any task to be boosted higher than 512
>
> It is certainly not that. That's the confusion I was trying to clear up in this
> note. The system values are _constraints_. It sets an upper bound on the
> maximum uclamp_min/max value the system will apply.
>
> For example if a task::uclamp_min=1024 but the system::uclamp_min=512 512, then
> effectively the task will only be boosted to 512. Once this restriction is left
> by setting system::uclamp_min=1024 again, then the task will get the boost
> value it requested.

ok, I got confused because uclamp -p PID  -min 512 - M 700 and uclamp
-s  -min 512 - M 700 look quite similar but their behaviors are quite
different.

I mean

uclamp -p PID -min 512 - M 700 will ensure that the task's utilization
will be always reported in the range [512:700]
The behavior is the same for the cgroup  with cpu.uclamp.min and cpu.uclamp.max

whereas

uclamp -s -min 512 - M 700 will do the opposite; i.e. the min of
task's utilization range will never be above 512

TBH I don't know how to make it clear that the behavior of -min is the
opposite between -p and -s

>
> I'm open to suggestions on how to better explain this..
>
> Thanks
>
> --
> Qais Yousef