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Message-ID: <20181107144252.GG9761@hirez.programming.kicks-ass.net>
Date: Wed, 7 Nov 2018 15:42:52 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Patrick Bellasi <patrick.bellasi@....com>
Cc: linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
Ingo Molnar <mingo@...hat.com>, Tejun Heo <tj@...nel.org>,
"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Viresh Kumar <viresh.kumar@...aro.org>,
Paul Turner <pjt@...gle.com>,
Quentin Perret <quentin.perret@....com>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Morten Rasmussen <morten.rasmussen@....com>,
Juri Lelli <juri.lelli@...hat.com>,
Todd Kjos <tkjos@...gle.com>,
Joel Fernandes <joelaf@...gle.com>,
Steve Muckle <smuckle@...gle.com>,
Suren Baghdasaryan <surenb@...gle.com>
Subject: Re: [PATCH v5 03/15] sched/core: uclamp: map TASK's clamp values
into CPU's clamp groups
On Wed, Nov 07, 2018 at 02:19:49PM +0000, Patrick Bellasi wrote:
> On 07-Nov 13:19, Peter Zijlstra wrote:
> > On Mon, Oct 29, 2018 at 06:32:57PM +0000, Patrick Bellasi wrote:
> > > +struct uclamp_se {
> > > + unsigned int value : SCHED_CAPACITY_SHIFT + 1;
> > > + unsigned int group_id : order_base_2(UCLAMP_GROUPS);
> >
> > Are you sure about ob2() ? seems weird we'll end up with 0 for
> > UCLAMP_GROUPS==1.
>
> So, we have:
>
> #define UCLAMP_GROUPS (CONFIG_UCLAMP_GROUPS_COUNT + 1)
>
> because one clamp group is always reserved for defaults.
> Thus, ob2(in) is always called with n>=2.
>
> ... should be safe no ?
+config UCLAMP_GROUPS_COUNT
+ int "Number of different utilization clamp values supported"
+ range 0 32
+ default 5
0+1 == 1
Increase the min range and you should be good I think.
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