linux-kernel - Re: [PATCH 3/3] sched/deadline: Use sched_dl_entity's dl_density in dl_task_fits

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Date:   Fri, 8 Jul 2022 14:34:23 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        Mel Gorman <mgorman@...e.de>, Ben Segall <bsegall@...gle.com>,
        Luca Abeni <luca.abeni@...tannapisa.it>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] sched/deadline: Use sched_dl_entity's dl_density in
 dl_task_fits_capacity()

On 06/07/2022 12:47, Vincent Guittot wrote:
> On Wed, 29 Jun 2022 at 14:21, Dietmar Eggemann <dietmar.eggemann@....com> wrote:

[...]

>>  static inline bool dl_task_fits_capacity(struct task_struct *p, int cpu)
>>  {
>>         unsigned long cap = arch_scale_cpu_capacity(cpu);
>>
>> -       return cap_scale(p->dl.dl_deadline, cap) >= p->dl.dl_runtime;
>> +       return cap >= p->dl.dl_density >> SCHED_CAPACITY_SHIFT;
> 
> There is no direct relation between BW_SHIFT and SCHED_CAPACITY_SHIFT
> and we can change one without modifying the other.
> 
> Should you use (BW_SHIFT-SCHED_CAPACITY_SHIFT) instead of SCHED_CAPACITY_SHIFT ?

Yes, that's better, similar to cpu_bw_dl(). Thanks!

[...]