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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