kernel/sched/ems/global_boost.c

/*
 * Global task boosting
 *
 * Copyright (C) 2018 Samsung Electronics Co., Ltd
 * Park Bumgyu <bumgyu.park@samsung.com>
 */

#include <linux/sched.h>
#include <linux/kobject.h>
#include <linux/ems.h>

#include <trace/events/ems.h>

#include "ems.h"

/*
 * Global boost manages each boosting request as a list so that it can support
 * boosting at the device driver level as well as user level. The list management
 * algorithm uses the priority-list same as pm_qos.
 */
static struct plist_head gb_list = PLIST_HEAD_INIT(gb_list);

static int gb_qos_value(void)
{
	if (plist_head_empty(&gb_list))
		return 0;

	return plist_last(&gb_list)->prio;
}

static DEFINE_SPINLOCK(gb_lock);

void gb_qos_update_request(struct gb_qos_request *req, u32 new_value)
{
	unsigned long flags;

	/* ignore if the value does not change */
	if (req->node.prio == new_value)
		return;

	spin_lock_irqsave(&gb_lock, flags);

	/*
	 * If the request already added to the list updates the value, remove
	 * the request from the list and add it again.
	 */
	if (req->active)
		plist_del(&req->node, &gb_list);
	else
		req->active = 1;

	plist_node_init(&req->node, new_value);
	plist_add(&req->node, &gb_list);

	trace_ems_global_boost(req->name, new_value);

	spin_unlock_irqrestore(&gb_lock, flags);
}

/* user level request, it is only set via sysfs */
static struct gb_qos_request gb_req_user =
{
	.name = "gb_req_user",
};

static ssize_t show_global_boost(struct kobject *kobj,
		struct kobj_attribute *attr, char *buf)
{
	struct gb_qos_request *req;
	int ret = 0;

	/* show all requests as well as user level */
	plist_for_each_entry(req, &gb_list, node)
		ret += snprintf(buf + ret, 30, "%s : %d\n",
				req->name, req->node.prio);

	return ret;
}

static ssize_t store_global_boost(struct kobject *kobj,
		struct kobj_attribute *attr, const char *buf,
		size_t count)
{
	unsigned int input;

	if (!sscanf(buf, "%d", &input))
		return -EINVAL;

	gb_qos_update_request(&gb_req_user, input);

	return count;
}

static struct kobj_attribute global_boost_attr =
__ATTR(global_boost, 0644, show_global_boost, store_global_boost);

static int __init init_gb_sysfs(void)
{
	int ret;

	ret = sysfs_create_file(ems_kobj, &global_boost_attr.attr);
	if (ret)
		pr_err("%s: faile to create sysfs file\n", __func__);

	return 0;
}
late_initcall(init_gb_sysfs);

/*
 * Returns the biggest value in the global boost list. In the current policy,
 * a value greater than 0 is unconditionally boosting. The size of the value
 * is meaningless.
 */
int global_boosted(void)
{
	u64 now = ktime_to_us(ktime_get());

	/* booting boost duration = 40s */
	if (now < 40 * USEC_PER_SEC)
		return 1;

	return gb_qos_value() > 0;
}

int global_boosting(struct task_struct *p)
{
	if (!global_boosted())
		return -1;

	return select_perf_cpu(p);
}