Messages in this thread |  | | Subject | Re: [PATCH v2] sched: rt: Make RT capacity aware | From | Dietmar Eggemann <> | Date | Wed, 30 Oct 2019 12:57:09 +0100 |
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On 09.10.19 12:46, Qais Yousef wrote:
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> Changes in v2: > - Use cpupri_find() to check the fitness of the task instead of > sprinkling find_lowest_rq() with several checks of > rt_task_fits_capacity(). > > The selected implementation opted to pass the fitness function as an > argument rather than call rt_task_fits_capacity() capacity which is > a cleaner to keep the logical separation of the 2 modules; but it > means the compiler has less room to optimize rt_task_fits_capacity() > out when it's a constant value.
I would prefer exporting rt_task_fits_capacity() sched-internally via kernel/sched/sched.h. Less code changes and the indication whether rt_task_fits_capacity() has to be used in cpupri_find() is already given by lowest_mask being !NULL or NULL.
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> +inline bool rt_task_fits_capacity(struct task_struct *p, int cpu) > +{ > + unsigned int min_cap; > + unsigned int max_cap; > + unsigned int cpu_cap;
Nit picking. Since we discussed it already,
I found this "Also please try to aggregate variables of the same type into a single line. There is no point in wasting screen space::" ;-)
https://lore.kernel.org/r/20181107171149.165693799@linutronix.de
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> @@ -2223,7 +2273,10 @@ static void switched_to_rt(struct rq *rq, struct task_struct *p) > */ > if (task_on_rq_queued(p) && rq->curr != p) { > #ifdef CONFIG_SMP > - if (p->nr_cpus_allowed > 1 && rq->rt.overloaded) > + bool need_to_push = rq->rt.overloaded || > + !rt_task_fits_capacity(p, cpu_of(rq)); > + > + if (p->nr_cpus_allowed > 1 && need_to_push) > rt_queue_push_tasks(rq); > #endif /* CONFIG_SMP */ > if (p->prio < rq->curr->prio && cpu_online(cpu_of(rq))) What happens to a always running CFS task which switches to RT? Luca introduced a special migrate callback (next to push and pull) specifically to deal with this scenario. A lot of new infrastructure for this one use case, but still, do we care for it in RT as well?
https://lore.kernel.org/r/20190506044836.2914-4-luca.abeni@santannapisa.it
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