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Message-ID: <71a0f27d-68e0-f118-c117-bae48f5f1996@arm.com>
Date: Wed, 7 Dec 2022 18:00:32 +0100
From: Dietmar Eggemann <dietmar.eggemann@....com>
To: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
"Peter Zijlstra (Intel)" <peterz@...radead.org>,
Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>
Cc: Ricardo Neri <ricardo.neri@...el.com>,
"Ravi V. Shankar" <ravi.v.shankar@...el.com>,
Ben Segall <bsegall@...gle.com>,
Daniel Bristot de Oliveira <bristot@...hat.com>,
Len Brown <len.brown@...el.com>, Mel Gorman <mgorman@...e.de>,
"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
Steven Rostedt <rostedt@...dmis.org>,
Tim Chen <tim.c.chen@...ux.intel.com>,
Valentin Schneider <vschneid@...hat.com>, x86@...nel.org,
"Joel Fernandes (Google)" <joel@...lfernandes.org>,
linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
"Tim C . Chen" <tim.c.chen@...el.com>
Subject: Re: [PATCH v2 06/22] sched/fair: Collect load-balancing stats for IPC
classes
On 28/11/2022 14:20, Ricardo Neri wrote:
[...]
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 224107278471..3a1d6c50a19b 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -9100,6 +9100,57 @@ group_type group_classify(unsigned int imbalance_pct,
> return group_has_spare;
> }
>
> +struct sg_lb_ipcc_stats {
> + int min_score; /* Min(score(rq->curr->ipcc)) */
> + int min_ipcc; /* Min(rq->curr->ipcc) */
> + long sum_score; /* Sum(score(rq->curr->ipcc)) */
> +};
Wouldn't it be cleaner to put `min_score`, `min_ipcc` and `sum_score`
into `struct sg_lb_stats` next to `ipcc_score_{after, before}` under the
same #ifdef CONFIG_IPC_CLASSES?
Looks like those IPCC stats would only be needed in the specific
condition under which update_sg_lb_stats_scores() is called?
> +#ifdef CONFIG_IPC_CLASSES
> +static void init_rq_ipcc_stats(struct sg_lb_ipcc_stats *sgcs)
> +{
> + *sgcs = (struct sg_lb_ipcc_stats) {
> + .min_score = INT_MAX,
> + };
> +}
> +
> +/** Called only if cpu_of(@rq) is not idle and has tasks running. */
> +static void update_sg_lb_ipcc_stats(struct sg_lb_ipcc_stats *sgcs,
> + struct rq *rq)
> +{
> + struct task_struct *curr;
> + unsigned short ipcc;
> + int score;
> +
> + if (!sched_ipcc_enabled())
> + return;
> +
> + curr = rcu_dereference(rq->curr);
> + if (!curr || (curr->flags & PF_EXITING) || is_idle_task(curr))
So the Idle task is excluded but RT, DL, (Stopper) tasks are not. Looks
weird if non-CFS tasks could influence CFS load-balancing.
AFAICS, RT and DL tasks could have p->ipcc != IPC_CLASS_UNCLASSIFIED?
[...]
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