On 20/05/20 15:42, Dietmar Eggemann wrote: > From: Luca Abeni <[email protected]> > > When a task has a runtime that cannot be served within the scheduling > deadline by any of the idle CPU (later_mask) the task is doomed to miss > its deadline. > > This can happen since the SCHED_DEADLINE admission control guarantees > only bounded tardiness and not the hard respect of all deadlines. > In this case try to select the idle CPU with the largest CPU capacity > to minimize tardiness. > > Favor task_cpu(p) if it has max capacity of !fitting CPUs so that > find_later_rq() can potentially still return it (most likely cache-hot) > early. > > Signed-off-by: Luca Abeni <[email protected]> > Signed-off-by: Dietmar Eggemann <[email protected]> > --- > kernel/sched/cpudeadline.c | 20 ++++++++++++++++---- > 1 file changed, 16 insertions(+), 4 deletions(-) > > diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c > index 8630f2a40a3f..8cb06c8c7eb1 100644 > --- a/kernel/sched/cpudeadline.c > +++ b/kernel/sched/cpudeadline.c > @@ -121,19 +121,31 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p, > > if (later_mask && > cpumask_and(later_mask, cp->free_cpus, p->cpus_ptr)) { > - int cpu; > + unsigned long cap, max_cap = 0; > + int cpu, max_cpu = -1; > > if (!static_branch_unlikely(&sched_asym_cpucapacity)) > return 1; > > /* Ensure the capacity of the CPUs fits the task. */ > for_each_cpu(cpu, later_mask) { > - if (!dl_task_fits_capacity(p, cpu)) > + if (!dl_task_fits_capacity(p, cpu)) { > cpumask_clear_cpu(cpu, later_mask); > + > + cap = capacity_orig_of(cpu); > + > + if (cap > max_cap || > + (cpu == task_cpu(p) && cap == max_cap)) { > + max_cap = cap; > + max_cpu = cpu; > + } > + } > } > > - if (!cpumask_empty(later_mask)) > - return 1; > + if (cpumask_empty(later_mask)) > + cpumask_set_cpu(max_cpu, later_mask); > + > + return 1; > } else { > int best_cpu = cpudl_maximum(cp); > > --
Acked-by: Juri Lelli <[email protected]>
