kernel/sched/tune.c

#include <linux/cgroup.h>
#include <linux/err.h>
#include <linux/percpu.h>
#include <linux/printk.h>
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/rcupdate.h>
#include <linux/slab.h>
#include <trace/events/sched.h>

#include "sched.h"
#include "tune.h"

unsigned int sysctl_sched_cfs_boost __read_mostly;

#ifdef CONFIG_CGROUP_SCHEDTUNE
static bool schedtune_initialized = false;
#endif /* CONFIG_CGROUP_SCHEDTUNE */

unsigned int sysctl_sched_cfs_boost __read_mostly;

extern struct target_nrg schedtune_target_nrg;

/* Performance Boost region (B) threshold params */
static int perf_boost_idx;

/* Performance Constraint region (C) threshold params */
static int perf_constrain_idx;

/**
 * Performance-Energy (P-E) Space thresholds constants
 */
struct threshold_params {
	int nrg_gain;
	int cap_gain;
};

/*
 * System specific P-E space thresholds constants
 */
static struct threshold_params
threshold_gains[] = {
	{ 0, 5 }, /*   < 10% */
	{ 1, 5 }, /*   < 20% */
	{ 2, 5 }, /*   < 30% */
	{ 3, 5 }, /*   < 40% */
	{ 4, 5 }, /*   < 50% */
	{ 5, 4 }, /*   < 60% */
	{ 5, 3 }, /*   < 70% */
	{ 5, 2 }, /*   < 80% */
	{ 5, 1 }, /*   < 90% */
	{ 5, 0 }  /* <= 100% */
};

static int
__schedtune_accept_deltas(int nrg_delta, int cap_delta,
			  int perf_boost_idx, int perf_constrain_idx)
{
	int payoff = -INT_MAX;
	int gain_idx = -1;

	/* Performance Boost (B) region */
	if (nrg_delta >= 0 && cap_delta > 0)
		gain_idx = perf_boost_idx;
	/* Performance Constraint (C) region */
	else if (nrg_delta < 0 && cap_delta <= 0)
		gain_idx = perf_constrain_idx;

	/* Default: reject schedule candidate */
	if (gain_idx == -1)
		return payoff;

	/*
	 * Evaluate "Performance Boost" vs "Energy Increase"
	 *
	 * - Performance Boost (B) region
	 *
	 *   Condition: nrg_delta > 0 && cap_delta > 0
	 *   Payoff criteria:
	 *     cap_gain / nrg_gain  < cap_delta / nrg_delta =
	 *     cap_gain * nrg_delta < cap_delta * nrg_gain
	 *   Note that since both nrg_gain and nrg_delta are positive, the
	 *   inequality does not change. Thus:
	 *
	 *     payoff = (cap_delta * nrg_gain) - (cap_gain * nrg_delta)
	 *
	 * - Performance Constraint (C) region
	 *
	 *   Condition: nrg_delta < 0 && cap_delta < 0
	 *   payoff criteria:
	 *     cap_gain / nrg_gain  > cap_delta / nrg_delta =
	 *     cap_gain * nrg_delta < cap_delta * nrg_gain
	 *   Note that since nrg_gain > 0 while nrg_delta < 0, the
	 *   inequality change. Thus:
	 *
	 *     payoff = (cap_delta * nrg_gain) - (cap_gain * nrg_delta)
	 *
	 * This means that, in case of same positive defined {cap,nrg}_gain
	 * for both the B and C regions, we can use the same payoff formula
	 * where a positive value represents the accept condition.
	 */
	payoff  = cap_delta * threshold_gains[gain_idx].nrg_gain;
	payoff -= nrg_delta * threshold_gains[gain_idx].cap_gain;

	return payoff;
}

#ifdef CONFIG_CGROUP_SCHEDTUNE

/*
 * EAS scheduler tunables for task groups.
 */

/* SchdTune tunables for a group of tasks */
struct schedtune {
	/* SchedTune CGroup subsystem */
	struct cgroup_subsys_state css;

	/* Boost group allocated ID */
	int idx;

	/* Boost value for tasks on that SchedTune CGroup */
	int boost;

#ifdef CONFIG_SCHED_WALT
	/* Toggle ability to override sched boost enabled */
	bool sched_boost_no_override;

	/*
	 * Controls whether a cgroup is eligible for sched boost or not. This
	 * can temporariliy be disabled by the kernel based on the no_override
	 * flag above.
	 */
	bool sched_boost_enabled;

	/*
	 * This tracks the default value of sched_boost_enabled and is used
	 * restore the value following any temporary changes to that flag.
	 */
	bool sched_boost_enabled_backup;

	/*
	 * Controls whether tasks of this cgroup should be colocated with each
	 * other and tasks of other cgroups that have the same flag turned on.
	 */
	bool colocate;

	/* Controls whether further updates are allowed to the colocate flag */
	bool colocate_update_disabled;
#endif /* CONFIG_SCHED_WALT */

	/* Performance Boost (B) region threshold params */
	int perf_boost_idx;

	/* Performance Constraint (C) region threshold params */
	int perf_constrain_idx;

	/* Hint to bias scheduling of tasks on that SchedTune CGroup
	 * towards idle CPUs */
	int prefer_idle;
};

static inline struct schedtune *css_st(struct cgroup_subsys_state *css)
{
	return container_of(css, struct schedtune, css);
}

static inline struct schedtune *task_schedtune(struct task_struct *tsk)
{
	return css_st(task_css(tsk, schedtune_cgrp_id));
}

static inline struct schedtune *parent_st(struct schedtune *st)
{
	return css_st(st->css.parent);
}

/*
 * SchedTune root control group
 * The root control group is used to defined a system-wide boosting tuning,
 * which is applied to all tasks in the system.
 * Task specific boost tuning could be specified by creating and
 * configuring a child control group under the root one.
 * By default, system-wide boosting is disabled, i.e. no boosting is applied
 * to tasks which are not into a child control group.
 */
static struct schedtune
root_schedtune = {
	.boost	= 0,
#ifdef CONFIG_SCHED_WALT
	.sched_boost_no_override = false,
	.sched_boost_enabled = true,
	.sched_boost_enabled_backup = true,
	.colocate = false,
	.colocate_update_disabled = false,
#endif
	.perf_boost_idx = 0,
	.perf_constrain_idx = 0,
	.prefer_idle = 0,
};

int
schedtune_accept_deltas(int nrg_delta, int cap_delta,
			struct task_struct *task)
{
	struct schedtune *ct;
	int perf_boost_idx;
	int perf_constrain_idx;

	/* Optimal (O) region */
	if (nrg_delta < 0 && cap_delta > 0) {
		trace_sched_tune_filter(nrg_delta, cap_delta, 0, 0, 1, 0);
		return INT_MAX;
	}

	/* Suboptimal (S) region */
	if (nrg_delta > 0 && cap_delta < 0) {
		trace_sched_tune_filter(nrg_delta, cap_delta, 0, 0, -1, 5);
		return -INT_MAX;
	}

	/* Get task specific perf Boost/Constraints indexes */
	rcu_read_lock();
	ct = task_schedtune(task);
	perf_boost_idx = ct->perf_boost_idx;
	perf_constrain_idx = ct->perf_constrain_idx;
	rcu_read_unlock();

	return __schedtune_accept_deltas(nrg_delta, cap_delta,
			perf_boost_idx, perf_constrain_idx);
}

/*
 * Maximum number of boost groups to support
 * When per-task boosting is used we still allow only limited number of
 * boost groups for two main reasons:
 * 1. on a real system we usually have only few classes of workloads which
 *    make sense to boost with different values (e.g. background vs foreground
 *    tasks, interactive vs low-priority tasks)
 * 2. a limited number allows for a simpler and more memory/time efficient
 *    implementation especially for the computation of the per-CPU boost
 *    value
 */
#define BOOSTGROUPS_COUNT 5

/* Array of configured boostgroups */
static struct schedtune *allocated_group[BOOSTGROUPS_COUNT] = {
	&root_schedtune,
	NULL,
};

/* SchedTune boost groups
 * Keep track of all the boost groups which impact on CPU, for example when a
 * CPU has two RUNNABLE tasks belonging to two different boost groups and thus
 * likely with different boost values.
 * Since on each system we expect only a limited number of boost groups, here
 * we use a simple array to keep track of the metrics required to compute the
 * maximum per-CPU boosting value.
 */
struct boost_groups {
	bool idle;
	/* Maximum boost value for all RUNNABLE tasks on a CPU */
	int boost_max;
	struct {
		/* The boost for tasks on that boost group */
		int boost;
		/* Count of RUNNABLE tasks on that boost group */
		unsigned tasks;
	} group[BOOSTGROUPS_COUNT];
	/* CPU's boost group locking */
	raw_spinlock_t lock;
};

/* Boost groups affecting each CPU in the system */
DEFINE_PER_CPU(struct boost_groups, cpu_boost_groups);

#ifdef CONFIG_SCHED_WALT
static inline void init_sched_boost(struct schedtune *st)
{
	st->sched_boost_no_override = false;
	st->sched_boost_enabled = true;
	st->sched_boost_enabled_backup = st->sched_boost_enabled;
	st->colocate = false;
	st->colocate_update_disabled = false;
}

bool same_schedtune(struct task_struct *tsk1, struct task_struct *tsk2)
{
	return task_schedtune(tsk1) == task_schedtune(tsk2);
}

void update_cgroup_boost_settings(void)
{
	int i;

	for (i = 0; i < BOOSTGROUPS_COUNT; i++) {
		if (!allocated_group[i])
			break;

		if (allocated_group[i]->sched_boost_no_override)
			continue;

		allocated_group[i]->sched_boost_enabled = false;
	}
}

void restore_cgroup_boost_settings(void)
{
	int i;

	for (i = 0; i < BOOSTGROUPS_COUNT; i++) {
		if (!allocated_group[i])
			break;

		allocated_group[i]->sched_boost_enabled =
			allocated_group[i]->sched_boost_enabled_backup;
	}
}

bool task_sched_boost(struct task_struct *p)
{
	struct schedtune *st = task_schedtune(p);

	return st->sched_boost_enabled;
}

static u64
sched_boost_override_read(struct cgroup_subsys_state *css,
			struct cftype *cft)
{
	struct schedtune *st = css_st(css);

	return st->sched_boost_no_override;
}

static int sched_boost_override_write(struct cgroup_subsys_state *css,
			struct cftype *cft, u64 override)
{
	struct schedtune *st = css_st(css);

	st->sched_boost_no_override = !!override;

	return 0;
}

#endif /* CONFIG_SCHED_WALT */

static void
schedtune_cpu_update(int cpu)
{
	struct boost_groups *bg;
	int boost_max;
	int idx;

	bg = &per_cpu(cpu_boost_groups, cpu);

	/* The root boost group is always active */
	boost_max = bg->group[0].boost;
	for (idx = 1; idx < BOOSTGROUPS_COUNT; ++idx) {
		/*
		 * A boost group affects a CPU only if it has
		 * RUNNABLE tasks on that CPU
		 */
		if (bg->group[idx].tasks == 0)
			continue;

		boost_max = max(boost_max, bg->group[idx].boost);
	}
	/* Ensures boost_max is non-negative when all cgroup boost values
	 * are neagtive. Avoids under-accounting of cpu capacity which may cause
	 * task stacking and frequency spikes.*/
	boost_max = max(boost_max, 0);
	bg->boost_max = boost_max;
}

static int
schedtune_boostgroup_update(int idx, int boost)
{
	struct boost_groups *bg;
	int cur_boost_max;
	int old_boost;
	int cpu;

	/* Update per CPU boost groups */
	for_each_possible_cpu(cpu) {
		bg = &per_cpu(cpu_boost_groups, cpu);

		/*
		 * Keep track of current boost values to compute the per CPU
		 * maximum only when it has been affected by the new value of
		 * the updated boost group
		 */
		cur_boost_max = bg->boost_max;
		old_boost = bg->group[idx].boost;

		/* Update the boost value of this boost group */
		bg->group[idx].boost = boost;

		/* Check if this update increase current max */
		if (boost > cur_boost_max && bg->group[idx].tasks) {
			bg->boost_max = boost;
			trace_sched_tune_boostgroup_update(cpu, 1, bg->boost_max);
			continue;
		}

		/* Check if this update has decreased current max */
		if (cur_boost_max == old_boost && old_boost > boost) {
			schedtune_cpu_update(cpu);
			trace_sched_tune_boostgroup_update(cpu, -1, bg->boost_max);
			continue;
		}

		trace_sched_tune_boostgroup_update(cpu, 0, bg->boost_max);
	}

	return 0;
}

#define ENQUEUE_TASK  1
#define DEQUEUE_TASK -1

static inline void
schedtune_tasks_update(struct task_struct *p, int cpu, int idx, int task_count)
{
	struct boost_groups *bg = &per_cpu(cpu_boost_groups, cpu);
	int tasks = bg->group[idx].tasks + task_count;

	/* Update boosted tasks count while avoiding to make it negative */
	bg->group[idx].tasks = max(0, tasks);

	trace_sched_tune_tasks_update(p, cpu, tasks, idx,
			bg->group[idx].boost, bg->boost_max);

	/* Boost group activation or deactivation on that RQ */
	if (tasks == 1 || tasks == 0)
		schedtune_cpu_update(cpu);
}

/*
 * NOTE: This function must be called while holding the lock on the CPU RQ
 */
void schedtune_enqueue_task(struct task_struct *p, int cpu)
{
	struct boost_groups *bg = &per_cpu(cpu_boost_groups, cpu);
	unsigned long irq_flags;
	struct schedtune *st;
	int idx;

	if (!unlikely(schedtune_initialized))
		return;

	/*
	 * When a task is marked PF_EXITING by do_exit() it's going to be
	 * dequeued and enqueued multiple times in the exit path.
	 * Thus we avoid any further update, since we do not want to change
	 * CPU boosting while the task is exiting.
	 */
	if (p->flags & PF_EXITING)
		return;

	/*
	 * Boost group accouting is protected by a per-cpu lock and requires
	 * interrupt to be disabled to avoid race conditions for example on
	 * do_exit()::cgroup_exit() and task migration.
	 */
	raw_spin_lock_irqsave(&bg->lock, irq_flags);
	rcu_read_lock();

	st = task_schedtune(p);
	idx = st->idx;

	schedtune_tasks_update(p, cpu, idx, ENQUEUE_TASK);

	rcu_read_unlock();
	raw_spin_unlock_irqrestore(&bg->lock, irq_flags);
}

int schedtune_can_attach(struct cgroup_taskset *tset)
{
	struct task_struct *task;
	struct cgroup_subsys_state *css;
	struct boost_groups *bg;
	struct rq_flags irq_flags;
	unsigned int cpu;
	struct rq *rq;
	int src_bg; /* Source boost group index */
	int dst_bg; /* Destination boost group index */
	int tasks;

	if (!unlikely(schedtune_initialized))
		return 0;


	cgroup_taskset_for_each(task, css, tset) {

		/*
		 * Lock the CPU's RQ the task is enqueued to avoid race
		 * conditions with migration code while the task is being
		 * accounted
		 */
		rq = lock_rq_of(task, &irq_flags);

		if (!task->on_rq) {
			unlock_rq_of(rq, task, &irq_flags);
			continue;
		}

		/*
		 * Boost group accouting is protected by a per-cpu lock and requires
		 * interrupt to be disabled to avoid race conditions on...
		 */
		cpu = cpu_of(rq);
		bg = &per_cpu(cpu_boost_groups, cpu);
		raw_spin_lock(&bg->lock);

		dst_bg = css_st(css)->idx;
		src_bg = task_schedtune(task)->idx;

		/*
		 * Current task is not changing boostgroup, which can
		 * happen when the new hierarchy is in use.
		 */
		if (unlikely(dst_bg == src_bg)) {
			raw_spin_unlock(&bg->lock);
			unlock_rq_of(rq, task, &irq_flags);
			continue;
		}

		/*
		 * This is the case of a RUNNABLE task which is switching its
		 * current boost group.
		 */

		/* Move task from src to dst boost group */
		tasks = bg->group[src_bg].tasks - 1;
		bg->group[src_bg].tasks = max(0, tasks);
		bg->group[dst_bg].tasks += 1;

		raw_spin_unlock(&bg->lock);
		unlock_rq_of(rq, task, &irq_flags);

		/* Update CPU boost group */
		if (bg->group[src_bg].tasks == 0 || bg->group[dst_bg].tasks == 1)
			schedtune_cpu_update(task_cpu(task));

	}

	return 0;
}

#ifdef CONFIG_SCHED_WALT
static u64 sched_boost_enabled_read(struct cgroup_subsys_state *css,
			struct cftype *cft)
{
	struct schedtune *st = css_st(css);

	return st->sched_boost_enabled;
}

static int sched_boost_enabled_write(struct cgroup_subsys_state *css,
			struct cftype *cft, u64 enable)
{
	struct schedtune *st = css_st(css);

	st->sched_boost_enabled = !!enable;
	st->sched_boost_enabled_backup = st->sched_boost_enabled;

	return 0;
}

static u64 sched_colocate_read(struct cgroup_subsys_state *css,
			struct cftype *cft)
{
	struct schedtune *st = css_st(css);

	return st->colocate;
}

static int sched_colocate_write(struct cgroup_subsys_state *css,
			struct cftype *cft, u64 colocate)
{
	struct schedtune *st = css_st(css);

	if (st->colocate_update_disabled)
		return -EPERM;

	st->colocate = !!colocate;
	st->colocate_update_disabled = true;
	return 0;
}

#else /* CONFIG_SCHED_WALT */

static inline void init_sched_boost(struct schedtune *st) { }

#endif /* CONFIG_SCHED_WALT */

void schedtune_cancel_attach(struct cgroup_taskset *tset)
{
	/* This can happen only if SchedTune controller is mounted with
	 * other hierarchies ane one of them fails. Since usually SchedTune is
	 * mouted on its own hierarcy, for the time being we do not implement
	 * a proper rollback mechanism */
	WARN(1, "SchedTune cancel attach not implemented");
}

/*
 * NOTE: This function must be called while holding the lock on the CPU RQ
 */
void schedtune_dequeue_task(struct task_struct *p, int cpu)
{
	struct boost_groups *bg = &per_cpu(cpu_boost_groups, cpu);
	unsigned long irq_flags;
	struct schedtune *st;
	int idx;

	if (!unlikely(schedtune_initialized))
		return;

	/*
	 * When a task is marked PF_EXITING by do_exit() it's going to be
	 * dequeued and enqueued multiple times in the exit path.
	 * Thus we avoid any further update, since we do not want to change
	 * CPU boosting while the task is exiting.
	 * The last dequeue is already enforce by the do_exit() code path
	 * via schedtune_exit_task().
	 */
	if (p->flags & PF_EXITING)
		return;

	/*
	 * Boost group accouting is protected by a per-cpu lock and requires
	 * interrupt to be disabled to avoid race conditions on...
	 */
	raw_spin_lock_irqsave(&bg->lock, irq_flags);
	rcu_read_lock();

	st = task_schedtune(p);
	idx = st->idx;

	schedtune_tasks_update(p, cpu, idx, DEQUEUE_TASK);

	rcu_read_unlock();
	raw_spin_unlock_irqrestore(&bg->lock, irq_flags);
}

void schedtune_exit_task(struct task_struct *tsk)
{
	struct schedtune *st;
	struct rq_flags irq_flags;
	unsigned int cpu;
	struct rq *rq;
	int idx;

	if (!unlikely(schedtune_initialized))
		return;

	rq = lock_rq_of(tsk, &irq_flags);
	rcu_read_lock();

	cpu = cpu_of(rq);
	st = task_schedtune(tsk);
	idx = st->idx;
	schedtune_tasks_update(tsk, cpu, idx, DEQUEUE_TASK);

	rcu_read_unlock();
	unlock_rq_of(rq, tsk, &irq_flags);
}

int schedtune_cpu_boost(int cpu)
{
	struct boost_groups *bg;

	bg = &per_cpu(cpu_boost_groups, cpu);
	return bg->boost_max;
}

int schedtune_task_boost(struct task_struct *p)
{
	struct schedtune *st;
	int task_boost;

	/* Get task boost value */
	rcu_read_lock();
	st = task_schedtune(p);
	task_boost = st->boost;
	rcu_read_unlock();

	return task_boost;
}

int schedtune_prefer_idle(struct task_struct *p)
{
	struct schedtune *st;
	int prefer_idle;

	/* Get prefer_idle value */
	rcu_read_lock();
	st = task_schedtune(p);
	prefer_idle = st->prefer_idle;
	rcu_read_unlock();

	return prefer_idle;
}

static u64
prefer_idle_read(struct cgroup_subsys_state *css, struct cftype *cft)
{
	struct schedtune *st = css_st(css);

	return st->prefer_idle;
}

static int
prefer_idle_write(struct cgroup_subsys_state *css, struct cftype *cft,
	    u64 prefer_idle)
{
	struct schedtune *st = css_st(css);
	st->prefer_idle = prefer_idle;

	return 0;
}

static s64
boost_read(struct cgroup_subsys_state *css, struct cftype *cft)
{
	struct schedtune *st = css_st(css);

	return st->boost;
}

#ifdef CONFIG_SCHED_WALT
static void schedtune_attach(struct cgroup_taskset *tset)
{
	struct task_struct *task;
	struct cgroup_subsys_state *css;
	struct schedtune *st;
	bool colocate;

	cgroup_taskset_first(tset, &css);
	st = css_st(css);

	colocate = st->colocate;

	cgroup_taskset_for_each(task, css, tset)
		sync_cgroup_colocation(task, colocate);

}
#endif

static int
boost_write(struct cgroup_subsys_state *css, struct cftype *cft,
	    s64 boost)
{
	struct schedtune *st = css_st(css);
	unsigned threshold_idx;
	int boost_pct;

	if (boost < -100 || boost > 100)
		return -EINVAL;
	boost_pct = boost;

	/*
	 * Update threshold params for Performance Boost (B)
	 * and Performance Constraint (C) regions.
	 * The current implementatio uses the same cuts for both
	 * B and C regions.
	 */
	threshold_idx = clamp(boost_pct, 0, 99) / 10;
	st->perf_boost_idx = threshold_idx;
	st->perf_constrain_idx = threshold_idx;

	st->boost = boost;
	if (css == &root_schedtune.css) {
		sysctl_sched_cfs_boost = boost;
		perf_boost_idx  = threshold_idx;
		perf_constrain_idx  = threshold_idx;
	}

	/* Update CPU boost */
	schedtune_boostgroup_update(st->idx, st->boost);

	trace_sched_tune_config(st->boost);

	return 0;
}

static struct cftype files[] = {
#ifdef CONFIG_SCHED_WALT
	{
		.name = "sched_boost_no_override",
		.read_u64 = sched_boost_override_read,
		.write_u64 = sched_boost_override_write,
	},
	{
		.name = "sched_boost_enabled",
		.read_u64 = sched_boost_enabled_read,
		.write_u64 = sched_boost_enabled_write,
	},
	{
		.name = "colocate",
		.read_u64 = sched_colocate_read,
		.write_u64 = sched_colocate_write,
	},
#endif
	{
		.name = "boost",
		.read_s64 = boost_read,
		.write_s64 = boost_write,
	},
	{
		.name = "prefer_idle",
		.read_u64 = prefer_idle_read,
		.write_u64 = prefer_idle_write,
	},
	{ }	/* terminate */
};


static int
schedtune_boostgroup_init(struct schedtune *st)
{
	struct boost_groups *bg;
	int cpu;

	/* Keep track of allocated boost groups */
	allocated_group[st->idx] = st;

	/* Initialize the per CPU boost groups */
	for_each_possible_cpu(cpu) {
		bg = &per_cpu(cpu_boost_groups, cpu);
		bg->group[st->idx].boost = 0;
		bg->group[st->idx].tasks = 0;
	}

	return 0;
}

static struct cgroup_subsys_state *
schedtune_css_alloc(struct cgroup_subsys_state *parent_css)
{
	struct schedtune *st;
	int idx;

	if (!parent_css)
		return &root_schedtune.css;

	/* Allow only single level hierachies */
	if (parent_css != &root_schedtune.css) {
		pr_err("Nested SchedTune boosting groups not allowed\n");
		return ERR_PTR(-ENOMEM);
	}

	/* Allow only a limited number of boosting groups */
	for (idx = 1; idx < BOOSTGROUPS_COUNT; ++idx)
		if (!allocated_group[idx])
			break;
	if (idx == BOOSTGROUPS_COUNT) {
		pr_err("Trying to create more than %d SchedTune boosting groups\n",
		       BOOSTGROUPS_COUNT);
		return ERR_PTR(-ENOSPC);
	}

	st = kzalloc(sizeof(*st), GFP_KERNEL);
	if (!st)
		goto out;

	/* Initialize per CPUs boost group support */
	st->idx = idx;
	init_sched_boost(st);
	if (schedtune_boostgroup_init(st))
		goto release;

	return &st->css;

release:
	kfree(st);
out:
	return ERR_PTR(-ENOMEM);
}

static void
schedtune_boostgroup_release(struct schedtune *st)
{
	/* Reset this boost group */
	schedtune_boostgroup_update(st->idx, 0);

	/* Keep track of allocated boost groups */
	allocated_group[st->idx] = NULL;
}

static void
schedtune_css_free(struct cgroup_subsys_state *css)
{
	struct schedtune *st = css_st(css);

	schedtune_boostgroup_release(st);
	kfree(st);
}

struct cgroup_subsys schedtune_cgrp_subsys = {
	.css_alloc	= schedtune_css_alloc,
	.css_free	= schedtune_css_free,
	.allow_attach	= subsys_cgroup_allow_attach,
	.attach		= schedtune_attach,
	.can_attach     = schedtune_can_attach,
	.cancel_attach  = schedtune_cancel_attach,
	.legacy_cftypes	= files,
	.early_init	= 1,
};

static inline void
schedtune_init_cgroups(void)
{
	struct boost_groups *bg;
	int cpu;

	/* Initialize the per CPU boost groups */
	for_each_possible_cpu(cpu) {
		bg = &per_cpu(cpu_boost_groups, cpu);
		memset(bg, 0, sizeof(struct boost_groups));
		raw_spin_lock_init(&bg->lock);
	}

	pr_info("schedtune: configured to support %d boost groups\n",
		BOOSTGROUPS_COUNT);

	schedtune_initialized = true;
}

#else /* CONFIG_CGROUP_SCHEDTUNE */

int
schedtune_accept_deltas(int nrg_delta, int cap_delta,
			struct task_struct *task)
{
	/* Optimal (O) region */
	if (nrg_delta < 0 && cap_delta > 0) {
		trace_sched_tune_filter(nrg_delta, cap_delta, 0, 0, 1, 0);
		return INT_MAX;
	}

	/* Suboptimal (S) region */
	if (nrg_delta > 0 && cap_delta < 0) {
		trace_sched_tune_filter(nrg_delta, cap_delta, 0, 0, -1, 5);
		return -INT_MAX;
	}

	return __schedtune_accept_deltas(nrg_delta, cap_delta,
			perf_boost_idx, perf_constrain_idx);
}

#endif /* CONFIG_CGROUP_SCHEDTUNE */

int
sysctl_sched_cfs_boost_handler(struct ctl_table *table, int write,
			       void __user *buffer, size_t *lenp,
			       loff_t *ppos)
{
	int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
	unsigned threshold_idx;
	int boost_pct;

	if (ret || !write)
		return ret;

	if (sysctl_sched_cfs_boost < -100 || sysctl_sched_cfs_boost > 100)
		return -EINVAL;
	boost_pct = sysctl_sched_cfs_boost;

	/*
	 * Update threshold params for Performance Boost (B)
	 * and Performance Constraint (C) regions.
	 * The current implementatio uses the same cuts for both
	 * B and C regions.
	 */
	threshold_idx = clamp(boost_pct, 0, 99) / 10;
	perf_boost_idx = threshold_idx;
	perf_constrain_idx = threshold_idx;

	return 0;
}

#ifdef CONFIG_SCHED_DEBUG
static void
schedtune_test_nrg(unsigned long delta_pwr)
{
	unsigned long test_delta_pwr;
	unsigned long test_norm_pwr;
	int idx;

	/*
	 * Check normalization constants using some constant system
	 * energy values
	 */
	pr_info("schedtune: verify normalization constants...\n");
	for (idx = 0; idx < 6; ++idx) {
		test_delta_pwr = delta_pwr >> idx;

		/* Normalize on max energy for target platform */
		test_norm_pwr = reciprocal_divide(
					test_delta_pwr << SCHED_CAPACITY_SHIFT,
					schedtune_target_nrg.rdiv);

		pr_info("schedtune: max_pwr/2^%d: %4lu => norm_pwr: %5lu\n",
			idx, test_delta_pwr, test_norm_pwr);
	}
}
#else
#define schedtune_test_nrg(delta_pwr)
#endif

/*
 * Compute the min/max power consumption of a cluster and all its CPUs
 */
static void
schedtune_add_cluster_nrg(
		struct sched_domain *sd,
		struct sched_group *sg,
		struct target_nrg *ste)
{
	struct sched_domain *sd2;
	struct sched_group *sg2;

	struct cpumask *cluster_cpus;
	char str[32];

	unsigned long min_pwr;
	unsigned long max_pwr;
	int cpu;

	/* Get Cluster energy using EM data for the first CPU */
	cluster_cpus = sched_group_cpus(sg);
	snprintf(str, 32, "CLUSTER[%*pbl]",
		 cpumask_pr_args(cluster_cpus));

	min_pwr = sg->sge->idle_states[sg->sge->nr_idle_states - 1].power;
	max_pwr = sg->sge->cap_states[sg->sge->nr_cap_states - 1].power;
	pr_info("schedtune: %-17s min_pwr: %5lu max_pwr: %5lu\n",
		str, min_pwr, max_pwr);

	/*
	 * Keep track of this cluster's energy in the computation of the
	 * overall system energy
	 */
	ste->min_power += min_pwr;
	ste->max_power += max_pwr;

	/* Get CPU energy using EM data for each CPU in the group */
	for_each_cpu(cpu, cluster_cpus) {
		/* Get a SD view for the specific CPU */
		for_each_domain(cpu, sd2) {
			/* Get the CPU group */
			sg2 = sd2->groups;
			min_pwr = sg2->sge->idle_states[sg2->sge->nr_idle_states - 1].power;
			max_pwr = sg2->sge->cap_states[sg2->sge->nr_cap_states - 1].power;

			ste->min_power += min_pwr;
			ste->max_power += max_pwr;

			snprintf(str, 32, "CPU[%d]", cpu);
			pr_info("schedtune: %-17s min_pwr: %5lu max_pwr: %5lu\n",
				str, min_pwr, max_pwr);

			/*
			 * Assume we have EM data only at the CPU and
			 * the upper CLUSTER level
			 */
			break;
		}
	}
}

/*
 * Initialize the constants required to compute normalized energy.
 * The values of these constants depends on the EM data for the specific
 * target system and topology.
 * Thus, this function is expected to be called by the code
 * that bind the EM to the topology information.
 */
static int
schedtune_init(void)
{
	struct target_nrg *ste = &schedtune_target_nrg;
	unsigned long delta_pwr = 0;
	struct sched_domain *sd;
	struct sched_group *sg;

	pr_info("schedtune: init normalization constants...\n");
	ste->max_power = 0;
	ste->min_power = 0;

	rcu_read_lock();

	/*
	 * When EAS is in use, we always have a pointer to the highest SD
	 * which provides EM data.
	 */
	sd = rcu_dereference(per_cpu(sd_ea, cpumask_first(cpu_online_mask)));
	if (!sd) {
		pr_info("schedtune: no energy model data\n");
		goto nodata;
	}

	sg = sd->groups;
	do {
		schedtune_add_cluster_nrg(sd, sg, ste);
	} while (sg = sg->next, sg != sd->groups);

	rcu_read_unlock();

	pr_info("schedtune: %-17s min_pwr: %5lu max_pwr: %5lu\n",
		"SYSTEM", ste->min_power, ste->max_power);

	/* Compute normalization constants */
	delta_pwr = ste->max_power - ste->min_power;
	ste->rdiv = reciprocal_value(delta_pwr);
	pr_info("schedtune: using normalization constants mul: %u sh1: %u sh2: %u\n",
		ste->rdiv.m, ste->rdiv.sh1, ste->rdiv.sh2);

	schedtune_test_nrg(delta_pwr);

#ifdef CONFIG_CGROUP_SCHEDTUNE
	schedtune_init_cgroups();
#else
	pr_info("schedtune: configured to support global boosting only\n");
#endif /* CONFIG_CGROUP_SCHEDTUNE */

	return 0;

nodata:
	rcu_read_unlock();
	return -EINVAL;
}
postcore_initcall(schedtune_init);