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SubjectRe: [PATCH 1/7] sched/core: uclamp: add CPU clamp groups accounting
On Fri, Apr 13, 2018 at 11:30:05AM +0200, Peter Zijlstra wrote:
> On Mon, Apr 09, 2018 at 05:56:09PM +0100, Patrick Bellasi wrote:
> > +struct uclamp_group {
> > + /* Utilization clamp value for tasks on this clamp group */
> > + int value;
> > + /* Number of RUNNABLE tasks on this clamp group */
> > + int tasks;
> > +};
>
> > +struct uclamp_cpu {
> > + /* Utilization clamp value for a CPU */
> > + int value;
> > + /* Utilization clamp groups affecting this CPU */
> > + struct uclamp_group group[CONFIG_UCLAMP_GROUPS_COUNT + 1];
> > +};
>
> > @@ -811,6 +885,11 @@ struct rq {
> > unsigned long cpu_capacity;
> > unsigned long cpu_capacity_orig;
> >
> > +#ifdef CONFIG_UCLAMP_TASK
> > + /* util_{min,max} clamp values based on CPU's active tasks */
> > + struct uclamp_cpu uclamp[UCLAMP_CNT];
> > +#endif
> > +
> > struct callback_head *balance_callback;
> >
> > unsigned char idle_balance;
>
> So that is:
>
> struct rq {
>
> struct uclamp_cpu {
> int value;
>
> /* 4 byte hole */
>
> struct uclamp_group {
> int value;
> int tasks;
> } [COUNT + 1]; // size: COUNT+2 * 8 [bytes]
>
> } [2]; // size: 2 * COUNT+2 * 8 [bytes]
>
> };

Note that you can slightly compress the data structure if you do
something like:

struct rq {

int active_clamp[2];

struct uclamp_group {
int value;
int task;
} [COUNT + 1][2]; // XXX check array order of C
};

It also avoids the active values being split over 2 lines; and we need
those values every time, even if there are no active clamp tasks on the
system.

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