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Date: Thu, 21 Nov 2013 09:41:50 -0500 From: Steven Rostedt <rostedt@...dmis.org> To: Juri Lelli <juri.lelli@...il.com> Cc: peterz@...radead.org, tglx@...utronix.de, mingo@...hat.com, oleg@...hat.com, fweisbec@...il.com, darren@...art.com, johan.eker@...csson.com, p.faure@...tech.ch, linux-kernel@...r.kernel.org, claudio@...dence.eu.com, michael@...rulasolutions.com, fchecconi@...il.com, tommaso.cucinotta@...up.it, nicola.manica@...i.unitn.it, luca.abeni@...tn.it, dhaval.giani@...il.com, hgu1972@...il.com, paulmck@...ux.vnet.ibm.com, raistlin@...ux.it, insop.song@...il.com, liming.wang@...driver.com, jkacur@...hat.com, harald.gustafsson@...csson.com, vincent.guittot@...aro.org, bruce.ashfield@...driver.com Subject: Re: [PATCH 04/14] sched: SCHED_DEADLINE SMP-related data structures & logic. On Thu, 21 Nov 2013 15:13:28 +0100 Juri Lelli <juri.lelli@...il.com> wrote: ; > >> + > >> +#ifdef CONFIG_SMP > >> + /* zero means no -deadline tasks */ > > > > I'm curious to why you add the '-' to -deadline. > > > > I guess "deadline tasks" is too much generic; "SCHED_DEADLINE tasks" too long; > "DL" or "-dl" can be associated to "download". Nothing special in the end, just > tought it was a reasonable abbreviation. Yeah, keep the -deadline, as that makes it more searchable. > >> +static int latest_cpu_find(struct cpumask *span, > >> + struct task_struct *task, > >> + struct cpumask *later_mask) > >> +{ > >> + const struct sched_dl_entity *dl_se = &task->dl; > >> + int cpu, found = -1, best = 0; > >> + u64 max_dl = 0; > >> + > >> + for_each_cpu(cpu, span) { > >> + struct rq *rq = cpu_rq(cpu); > >> + struct dl_rq *dl_rq = &rq->dl; > >> + > >> + if (cpumask_test_cpu(cpu, &task->cpus_allowed) && > >> + (!dl_rq->dl_nr_running || dl_time_before(dl_se->deadline, > >> + dl_rq->earliest_dl.curr))) { > >> + if (later_mask) > >> + cpumask_set_cpu(cpu, later_mask); > >> + if (!best && !dl_rq->dl_nr_running) { > >> + best = 1; > >> + found = cpu; > >> + } else if (!best && > >> + dl_time_before(max_dl, > >> + dl_rq->earliest_dl.curr)) { > > > > Ug, the above is hard to read. What about: > > > > if (!best) { > > if (!dl_rq->dl_nr_running) { > > best = 1; > > found = cpu; > > } elsif (dl_time_before(...)) { > > ... > > } > > } > > > > This is completely removed in 13/14. I don't like it either, but since we end > up removing this mess, do you think we still have to fix this here? OK, if it gets removed later (I haven't hit patch 13 yet), then it should be fine. > > > Also, I would think dl should be nice to rt as well. There may be a > > idle CPU or a non rt task, and this could pick a CPU running an RT > > task. Worse yet, that RT task may be pinned to that CPU. > > > > Well, in 13/14 we introduce a free_cpus mask. A CPU is considered free if it > doesn't have any -deadline task running. We can modify that excluding also CPUs > running RT tasks, but I have to think a bit if we can do this also from -rt code. > > > We should be able to incorporate cpuprio_find() to be dl aware too. > > That is, work for both -rt and -dl. > > > > Like checking if a -dl task is running on the cpu chosen for pushing an -rt > task, and continue searching in that case. Yep, and also, it could perhaps be used for knowing where to push a -dl task too. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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