linux-kernel - Re: [PATCH v2] sched: Provide USF for the portable equipment.

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Message-ID: <67e5566b-2ec5-0a1d-87e1-88e90a8fa715@arm.com>
Date:   Fri, 31 Jul 2020 16:25:56 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Dongdong Yang <contribute.kernel@...il.com>,
        gregkh@...uxfoundation.org, rjw@...ysocki.net,
        viresh.kumar@...aro.org, mingo@...hat.com, peterz@...radead.org,
        juri.lelli@...hat.com, vincent.guittot@...aro.org,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de
Cc:     linux-kernel@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-pm@...r.kernel.org, yangdongdong@...omi.com,
        tanggeliang@...omi.com, taojun@...omi.com, huangqiwu@...omi.com,
        rocking@...ux.alibaba.com, fengwei@...omi.com,
        zhangguoquan@...omi.com, gulinghua@...omi.com, duhui@...omi.com
Subject: Re: [PATCH v2] sched: Provide USF for the portable equipment.

On 31/07/2020 14:46, Dongdong Yang wrote:
> From: Dongdong Yang <yangdongdong@...omi.com>

[...]

> +	if (unlikely(usf_vdev.enable_debug))
> +		trace_printk
> +		    ("%s: cpu_id=%d non_ux=%d usf_up=%d usf_down=%d util=%lu\n",
> +		     USF_TAG, cpuid, usf_vdev.usf_non_ux,
> +		     usf_vdev.usf_up_l0, usf_vdev.usf_down, *util);

trace_printk in code ?

> +static int usf_lcd_notifier(struct notifier_block *nb,
> +			    unsigned long val, void *data)
> +{
> +	struct fb_event *evdata = data;
> +	unsigned int blank;
> +
> +	if (!evdata)
> +		return 0;
> +
> +	if (val != FB_EVENT_BLANK)
> +		return 0;
> +
> +	if (evdata->data && val == FB_EVENT_BLANK) {
> +		blank = *(int *)(evdata->data);
> +
> +		switch (blank) {
> +		case FB_BLANK_POWERDOWN:
> +			usf_vdev.is_screen_on = 0;
> +			if (usf_vdev.sysctl_sched_usf_non_ux != 0)
> +				static_branch_enable(&adjust_task_pred_set);
> +			else
> +				static_branch_disable(&adjust_task_pred_set);
> +
> +			break;
> +
> +		case FB_BLANK_UNBLANK:
> +			usf_vdev.is_screen_on = 1;
> +			if (usf_vdev.sysctl_sched_usf_up_l0 != 0 ||
> +			    usf_vdev.sysctl_sched_usf_down != 0)
> +				static_branch_enable(&adjust_task_pred_set);
> +			else
> +				static_branch_disable(&adjust_task_pred_set);
> +			break;
> +		default:
> +			break;
> +		}
> +
> +		usf_vdev.is_sched_usf_enabled = 1;
> +		if (usf_vdev.enable_debug)
> +			trace_printk("%s : usf_vdev.is_screen_on:%d\n",
> +				     __func__, usf_vdev.is_screen_on);
> +	}
> +	return NOTIFY_OK;
> +}
> +
> +static struct notifier_block usf_lcd_nb = {
> +	.notifier_call = usf_lcd_notifier,
> +	.priority = INT_MAX,
> +};

Looks like those notifications should enable/disable the schedutil
extension adjust_task_pred_demand(). Who's calling them?

The 3 sched_usf_FOO sys files somehow have an influence here too. How
should this work?

I see a fb_register_client() in intera_monitor_init further below.

[...]

> +usf_attr_rw(sched_usf_up_l0_r);
> +usf_attr_rw(sched_usf_down_r);
> +usf_attr_rw(sched_usf_non_ux_r);

What can I do with these three files? What do they stand for?

root@...0:/sys/devices/system/cpu/sched_usf# ls
sched_usf_down_r  sched_usf_non_ux_r  sched_usf_up_l0_r

[...]

> +static int __init intera_monitor_init(void)
> +{
> +	int res = -1;
> +	struct attribute_group *attr_group;
> +
> +	res = fb_register_client(&usf_lcd_nb);
> +	if (res < 0) {
> +		pr_err("Failed to register usf_lcd_nb!\n");
> +		return res;

[...]