Messages in this thread Patch in this message | | | From | Dietmar Eggemann <> | Subject | [PATCH 3/3] sched/deadline: Use sched_dl_entity's dl_density in dl_task_fits_capacity() | Date | Wed, 29 Jun 2022 14:20:53 +0200 |
| |
Save a multiplication in dl_task_fits_capacity() by using already maintained per-sched_dl_entity (i.e. per-task) `dl_runtime/dl_deadline` (dl_density).
cap_scale(dl_deadline, cap) >= dl_runtime
dl_deadline * cap >> SCHED_CAPACITY_SHIFT >= dl_runtime
cap >= dl_runtime << SCHED_CAPACITY_SHIFT / dl_deadline
with BW_SHIFT = 2 x SCHED_CAPACITY_SHIFT
cap >= (dl_runtime << BW_SHIFT / dl_deadline) >> SCHED_CAPACITY_SHIFT
cap >= dl_density >> SCHED_CAPACITY_SHIFT
__sched_setscheduler()->__checkparam_dl() ensures that the 2 corner cases (if conditions) `runtime == RUNTIME_INF (-1)` and `period == 0` of to_ratio(deadline, runtime) are not met when setting dl_density in __sched_setscheduler()-> __setscheduler_params()->__setparam_dl().
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com> --- kernel/sched/sched.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 79f65a6799c6..555f58d6c3a6 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -324,15 +324,15 @@ struct dl_bw { * Verify the fitness of task @p to run on @cpu taking into account the * CPU original capacity and the runtime/deadline ratio of the task. * - * The function will return true if the CPU original capacity of the - * @cpu scaled by SCHED_CAPACITY_SCALE >= runtime/deadline ratio of the - * task and false otherwise. + * The function will return true if the original capacity of @cpu is + * greater than or equal to task's deadline density right shifted by + * SCHED_CAPACITY_SHIFT and false otherwise. */ 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; } extern void init_dl_bw(struct dl_bw *dl_b); -- 2.25.1
| |