Re: [PATCH v7 03/15] sched/core: uclamp: Add system default clamps

Patrick Bellasi
2019-03-15T13:41:39Z

On 13-Mar 21:10, Peter Zijlstra wrote:
> On Wed, Mar 13, 2019 at 05:09:40PM +0000, Patrick Bellasi wrote:
>
> > Yes, that should be possible... will look into splitting this out in
> > v8 to have something like:
> >
> > ---8<---
> > struct uclamp_req {
> > /* Clamp value "requested" by a scheduling entity */
> > unsigned int value : bits_per(SCHED_CAPACITY_SCALE);
> > unsigned int bucket_id : bits_per(UCLAMP_BUCKETS);
> > unsigned int active : 1;
> > unsigned int user_defined : 1;
> > }
> >
> > struct uclamp_eff {
> > unsigned int value : bits_per(SCHED_CAPACITY_SCALE);
> > unsigned int bucket_id : bits_per(UCLAMP_BUCKETS);
> > }
>
> No, have _1_ type. There is no point what so ever to splitting this.
>
> Also, what's @user_defined about, I don't think I've seen that in the
> parent patch.

That's a flag added by one of the following patches, but with the
change you are suggesting below...

> > struct task_struct {
> > // ...
> > #ifdef CONFIG_UCLAMP_TASK
> > struct uclamp_req uclamp_req[UCLAMP_CNT];
> > struct uclamp_eff uclamp_eff[UCLAMP_CNT];
>
> struct uclamp_se uclamp[UCLAMP_CNT];
> struct uclamp_se uclamp_req[UCLAMP_CNT];
>
> Where the first is the very same introduced in patch #1, and leaving it
> in place avoids having to update the sites already using that (or start
> #1 with the _eff name to avoid having to change things around?).
>
> > #endif
> > // ...
> > }
> >
> > static inline struct uclamp_eff
> > uclamp_eff_get(struct task_struct *p, unsigned int clamp_id)
> > {
> > struct uclamp_eff uc_eff = p->uclamp_eff[clamp_id];
>
> just this ^, these lines seem like a superfluous duplication:
>
> > uc_eff.bucket_id = p->uclamp_req[clamp_id].bucket_id;
> > uc_eff.value = p->uclamp_req[clamp_id].value;
>
>
> > if (unlikely(uc_eff.clamp_value > uclamp_default[clamp_id].value)) {
> > uc_eff.clamp_value = uclamp_default[clamp_id].value;
> > uc_eff.bucket_id = uclamp_default[clamp_id].bucket_id;
>
> and:
>
> uc = uclamp_default[clamp_id];

... with things like the above line it becomes quite tricky to exploit
the uclamp_se bitfield to track additional flags.

I'll try to remove the need for the "user_defined" flag, as long as we
have only the "active" you we can still manage to keep it in uclamp_se.

If instead we really need more flags, we will likely have to move them
into a separate bitfield. :/

>
> > }
> >
> > return uc_eff;
> > }
> >
> > static inline void
> > uclamp_eff_set(struct task_struct *p, unsigned int clamp_id)
> > {
> > p->uclamp_eff[clamp_id] = uclamp_eff_get(p, clamp_id);
> > }
> > ---8<---
> >
> > Is that what you mean ?
>
> Getting there :-)

Yeah... let see :)

--
#include <best/regards.h>

Patrick Bellasi