mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
synced 2025-01-15 11:37:47 +00:00
5e054bca44
pri_to_cpu[CPUPRI_IDLE=0] isn't used since cpupri_set(..., newpri) is
never called with newpri = MAX_PRIO (140).
Current mapping:
p->rt_priority p->prio newpri cpupri
-1 -1 (CPUPRI_INVALID)
140 0 (CPUPRI_IDLE)
100 1 (CPUPRI_NORMAL)
1 98 98 3
...
49 50 50 51
50 49 49 52
...
99 0 0 101
Even when cpupri was introduced with commit 6e0534f27819 ("sched: use a
2-d bitmap for searching lowest-pri CPU") in v2.6.27, only
(1) CPUPRI_INVALID (-1),
(2) MAX_RT_PRIO (100),
(3) an RT prio (RT1..RT99)
were used as newprio in cpupri_set(..., newpri) -> convert_prio(newpri).
MAX_RT_PRIO is used only in dec_rt_tasks() -> dec_rt_prio() ->
dec_rt_prio_smp() -> cpupri_set() in case of !rt_rq->rt_nr_running.
I.e. it stands for a non-rt task, including the IDLE task.
Commit 57785df5ac53 ("sched: Fix task priority bug") removed code in
v2.6.33 which did set the priority of the IDLE task to MAX_PRIO.
Although this happened after the introduction of cpupri, it didn't have
an effect on the values used for cpupri_set(..., newpri).
Remove CPUPRI_IDLE 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 2
...
49 50 50 50
50 49 49 51
...
99 0 0 100
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200922083934.19275-2-dietmar.eggemann@arm.com
29 lines
746 B
C
29 lines
746 B
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
|
|
#define CPUPRI_NR_PRIORITIES (MAX_RT_PRIO + 1)
|
|
|
|
#define CPUPRI_INVALID -1
|
|
#define CPUPRI_NORMAL 0
|
|
/* values 2-100 are RT priorities 0-99 */
|
|
|
|
struct cpupri_vec {
|
|
atomic_t count;
|
|
cpumask_var_t mask;
|
|
};
|
|
|
|
struct cpupri {
|
|
struct cpupri_vec pri_to_cpu[CPUPRI_NR_PRIORITIES];
|
|
int *cpu_to_pri;
|
|
};
|
|
|
|
#ifdef CONFIG_SMP
|
|
int cpupri_find(struct cpupri *cp, struct task_struct *p,
|
|
struct cpumask *lowest_mask);
|
|
int cpupri_find_fitness(struct cpupri *cp, struct task_struct *p,
|
|
struct cpumask *lowest_mask,
|
|
bool (*fitness_fn)(struct task_struct *p, int cpu));
|
|
void cpupri_set(struct cpupri *cp, int cpu, int pri);
|
|
int cpupri_init(struct cpupri *cp);
|
|
void cpupri_cleanup(struct cpupri *cp);
|
|
#endif
|