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1b08782ce3
pri_to_cpu[1] isn't used since cpupri_set(..., newpri) is
never called with newpri = 99.
The valid RT priorities RT1..RT99 (p->rt_priority = [1..99]) map into
cpupri (idx of pri_to_cpu[]) = [2..100]
Current mapping:
p->rt_priority p->prio newpri cpupri
-1 -1 (CPUPRI_INVALID)
100 0 (CPUPRI_NORMAL)
1 98 98 2
...
49 50 50 50
50 49 49 51
...
99 0 0 100
So cpupri = 1 isn't used.
Reduce the size of pri_to_cpu[] by 1 and adapt the cpupri
implementation accordingly. This will save a useless for loop with an
atomic_read in cpupri_find_fitness() calling __cpupri_find().
New mapping:
p->rt_priority p->prio newpri cpupri
-1 -1 (CPUPRI_INVALID)
100 0 (CPUPRI_NORMAL)
1 98 98 1
...
49 50 50 49
50 49 49 50
...
99 0 0 99
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200922083934.19275-3-dietmar.eggemann@arm.com
28 lines
744 B
C
28 lines
744 B
C
/* SPDX-License-Identifier: GPL-2.0 */
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#define CPUPRI_NR_PRIORITIES MAX_RT_PRIO
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#define CPUPRI_INVALID -1
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#define CPUPRI_NORMAL 0
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/* values 1-99 are for RT1-RT99 priorities */
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struct cpupri_vec {
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atomic_t count;
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cpumask_var_t mask;
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};
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struct cpupri {
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struct cpupri_vec pri_to_cpu[CPUPRI_NR_PRIORITIES];
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int *cpu_to_pri;
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};
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#ifdef CONFIG_SMP
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int cpupri_find(struct cpupri *cp, struct task_struct *p,
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struct cpumask *lowest_mask);
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int cpupri_find_fitness(struct cpupri *cp, struct task_struct *p,
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struct cpumask *lowest_mask,
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bool (*fitness_fn)(struct task_struct *p, int cpu));
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void cpupri_set(struct cpupri *cp, int cpu, int pri);
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int cpupri_init(struct cpupri *cp);
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void cpupri_cleanup(struct cpupri *cp);
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#endif
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