From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Qais Yousef <qais.yousef@arm.com>, Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Steven Rostedt <rostedt@goodmis.org>,
Pavan Kondeti <pkondeti@codeaurora.org>
Cc: Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] sched/rt: cpupri_find: implement fallback mechanism for !fit case
Date: Mon, 17 Feb 2020 20:09:24 +0100 [thread overview]
Message-ID: <c0772fca-0a4b-c88d-fdf2-5715fcf8447b@arm.com> (raw)
In-Reply-To: <20200214163949.27850-2-qais.yousef@arm.com>
On 14/02/2020 17:39, Qais Yousef wrote:
[...]
> /**
> * cpupri_find - find the best (lowest-pri) CPU in the system
> * @cp: The cpupri context
> @@ -62,80 +115,72 @@ int cpupri_find(struct cpupri *cp, struct task_struct *p,
> struct cpumask *lowest_mask,
> bool (*fitness_fn)(struct task_struct *p, int cpu))
> {
> - int idx = 0;
> int task_pri = convert_prio(p->prio);
> + int best_unfit_idx = -1;
> + int idx = 0, cpu;
>
> BUG_ON(task_pri >= CPUPRI_NR_PRIORITIES);
>
> for (idx = 0; idx < task_pri; idx++) {
> - struct cpupri_vec *vec = &cp->pri_to_cpu[idx];
> - int skip = 0;
>
> - if (!atomic_read(&(vec)->count))
> - skip = 1;
> - /*
> - * When looking at the vector, we need to read the counter,
> - * do a memory barrier, then read the mask.
> - *
> - * Note: This is still all racey, but we can deal with it.
> - * Ideally, we only want to look at masks that are set.
> - *
> - * If a mask is not set, then the only thing wrong is that we
> - * did a little more work than necessary.
> - *
> - * If we read a zero count but the mask is set, because of the
> - * memory barriers, that can only happen when the highest prio
> - * task for a run queue has left the run queue, in which case,
> - * it will be followed by a pull. If the task we are processing
> - * fails to find a proper place to go, that pull request will
> - * pull this task if the run queue is running at a lower
> - * priority.
> - */
> - smp_rmb();
> -
> - /* Need to do the rmb for every iteration */
> - if (skip)
> - continue;
> -
> - if (cpumask_any_and(p->cpus_ptr, vec->mask) >= nr_cpu_ids)
> + if (!__cpupri_find(cp, p, lowest_mask, idx))
> continue;
>
> - if (lowest_mask) {
> - int cpu;
Shouldn't we add an extra condition here?
+ if (!static_branch_unlikely(&sched_asym_cpucapacity))
+ return 1;
+
Otherwise non-heterogeneous systems have to got through this
for_each_cpu(cpu, lowest_mask) further below for no good reason.
> + if (!lowest_mask || !fitness_fn)
> + return 1;
>
> - cpumask_and(lowest_mask, p->cpus_ptr, vec->mask);
> + /* Ensure the capacity of the CPUs fit the task */
> + for_each_cpu(cpu, lowest_mask) {
> + if (!fitness_fn(p, cpu))
> + cpumask_clear_cpu(cpu, lowest_mask);
> + }
[...]
next prev parent reply other threads:[~2020-02-17 19:09 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-14 16:39 [PATCH 0/3] RT Capacity Awareness Improvements Qais Yousef
2020-02-14 16:39 ` [PATCH 1/3] sched/rt: cpupri_find: implement fallback mechanism for !fit case Qais Yousef
2020-02-17 17:07 ` Valentin Schneider
2020-02-17 23:34 ` Qais Yousef
2020-02-18 10:01 ` Valentin Schneider
2020-02-17 19:09 ` Dietmar Eggemann [this message]
2020-02-17 23:45 ` Qais Yousef
2020-02-18 9:53 ` Dietmar Eggemann
2020-02-18 17:28 ` Qais Yousef
2020-02-18 16:46 ` Steven Rostedt
2020-02-18 17:27 ` Qais Yousef
2020-02-18 18:03 ` Steven Rostedt
2020-02-18 18:52 ` Qais Yousef
2020-02-14 16:39 ` [PATCH 2/3] sched/rt: allow pulling unfitting task Qais Yousef
2020-02-17 9:10 ` Pavan Kondeti
2020-02-17 11:20 ` Qais Yousef
2020-02-19 13:43 ` Qais Yousef
2020-02-21 8:07 ` Pavan Kondeti
2020-02-21 11:08 ` Qais Yousef
2020-02-14 16:39 ` [PATCH 3/3] sched/rt: fix pushing unfit tasks to a better CPU Qais Yousef
2020-02-17 9:23 ` Pavan Kondeti
2020-02-17 13:53 ` Qais Yousef
2020-02-18 4:16 ` Pavan Kondeti
2020-02-18 17:47 ` Qais Yousef
2020-02-19 2:46 ` Pavan Kondeti
2020-02-19 10:46 ` Qais Yousef
2020-02-19 14:02 ` Qais Yousef
2020-02-21 8:15 ` Pavan Kondeti
2020-02-21 11:12 ` Qais Yousef
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