Messages in this thread | | | Subject | Re: [PATCH v2 5/6] sched/deadline: Make DL capacity-aware | From | Dietmar Eggemann <> | Date | Fri, 1 May 2020 18:12:07 +0200 |
| |
On 30/04/2020 15:10, Pavan Kondeti wrote: > On Mon, Apr 27, 2020 at 10:37:08AM +0200, Dietmar Eggemann wrote: >> From: Luca Abeni <luca.abeni@santannapisa.it>
[...]
>> @@ -1653,10 +1654,19 @@ select_task_rq_dl(struct task_struct *p, int cpu, int sd_flag, int flags) >> * other hand, if it has a shorter deadline, we >> * try to make it stay here, it might be important. >> */ >> - if (unlikely(dl_task(curr)) && >> - (curr->nr_cpus_allowed < 2 || >> - !dl_entity_preempt(&p->dl, &curr->dl)) && >> - (p->nr_cpus_allowed > 1)) { >> + select_rq = unlikely(dl_task(curr)) && >> + (curr->nr_cpus_allowed < 2 || >> + !dl_entity_preempt(&p->dl, &curr->dl)) && >> + p->nr_cpus_allowed > 1; >> + >> + /* >> + * Take the capacity of the CPU into account to >> + * ensure it fits the requirement of the task. >> + */ >> + if (static_branch_unlikely(&sched_asym_cpucapacity)) >> + select_rq |= !dl_task_fits_capacity(p, cpu); >> + >> + if (select_rq) { >> int target = find_later_rq(p); > > I see that find_later_rq() checks if the previous CPU is part of > later_mask and returns it immediately. So we don't migrate the > task in the case where there previous CPU can't fit the task and > there are no idle CPUs on which the task can fit. LGTM.
Hope I understand you here. I don't think that [patch 6/6] provides this already.
In case 'later_mask' has no fitting CPUs, 'max_cpu' is set in the otherwise empty 'later_mask'. But 'max_cpu' is not necessary task_cpu(p).
Example on Juno [L b b L L L] with thread0-0 (big task)
cpudl_find [thread0-0 2117] orig later_mask=0,3-4 later_mask=0 find_later_rq [thread0-0 2117] task_cpu=2 later_mask=0
A tweak could be added favor task_cpu(p) in case it is amongst the CPUs with the maximum capacity in cpudl_find() for the !fit case.
[...]
>> +/* >> + * 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. >> + */ >> +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; >> +} >> + > > This is same as > > return p->dl.dl_bw >> (BW_SHIFT - SCHED_CAPACITY_SHIFT) <= cap > > Correct? If yes, would it be better to use this?
We could use sched_dl_entity::dl_density (dl_runtime / dl_deadline) but then I would have to export BW_SHIFT.
| |