1 files changed, 621 insertions, 0 deletions
diff --git a/kernel/sched/tune.c b/kernel/sched/tune.c
new file mode 100644
index 000000000000..74a45606dc8c
--- /dev/null
+++ b/kernel/sched/tune.c
@@ -0,0 +1,621 @@
+#include <linux/cgroup.h>
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/percpu.h>
+#include <linux/printk.h>
+#include <linux/rcupdate.h>
+#include <linux/slab.h>
+
+#include <trace/events/sched.h>
+
+#include "sched.h"
+#include "tune.h"
+
+bool schedtune_initialized = false;
+extern struct reciprocal_value schedtune_spc_rdiv;
+
+/* We hold schedtune boost in effect for at least this long */
+#define SCHEDTUNE_BOOST_HOLD_NS 50000000ULL
+
+/*
+ * 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;
+
+	/* 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 css ? container_of(css, struct schedtune, css) : NULL;
+}
+
+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,
+	.prefer_idle = 0,
+};
+
+/*
+ * 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 {
+	/* Maximum boost value for all RUNNABLE tasks on a CPU */
+	bool idle;
+	int boost_max;
+	u64 boost_ts;
+	struct {
+		/* The boost for tasks on that boost group */
+		int boost;
+		/* Count of RUNNABLE tasks on that boost group */
+		unsigned tasks;
+		/* Timestamp of boost activation */
+		u64 ts;
+	} 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);
+
+static inline bool schedtune_boost_timeout(u64 now, u64 ts)
+{
+	return ((now - ts) > SCHEDTUNE_BOOST_HOLD_NS);
+}
+
+static inline bool
+schedtune_boost_group_active(int idx, struct boost_groups* bg, u64 now)
+{
+	if (bg->group[idx].tasks)
+		return true;
+
+	return !schedtune_boost_timeout(now, bg->group[idx].ts);
+}
+
+static void
+schedtune_cpu_update(int cpu, u64 now)
+{
+	struct boost_groups *bg = &per_cpu(cpu_boost_groups, cpu);
+	int boost_max;
+	u64 boost_ts;
+	int idx;
+
+	/* The root boost group is always active */
+	boost_max = bg->group[0].boost;
+	boost_ts = now;
+	for (idx = 1; idx < BOOSTGROUPS_COUNT; ++idx) {
+		/*
+		 * A boost group affects a CPU only if it has
+		 * RUNNABLE tasks on that CPU or it has hold
+		 * in effect from a previous task.
+		 */
+		if (!schedtune_boost_group_active(idx, bg, now))
+			continue;
+
+		/* This boost group is active */
+		if (boost_max > bg->group[idx].boost)
+			continue;
+
+		boost_max = bg->group[idx].boost;
+		boost_ts =  bg->group[idx].ts;
+	}
+	/* 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;
+	bg->boost_ts = boost_ts;
+}
+
+static int
+schedtune_boostgroup_update(int idx, int boost)
+{
+	struct boost_groups *bg;
+	int cur_boost_max;
+	int old_boost;
+	int cpu;
+	u64 now;
+
+	/* 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 */
+		now = sched_clock_cpu(cpu);
+		if (boost > cur_boost_max &&
+			schedtune_boost_group_active(idx, bg, now)) {
+			bg->boost_max = boost;
+			bg->boost_ts = bg->group[idx].ts;
+
+			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, now);
+			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 bool
+schedtune_update_timestamp(struct task_struct *p)
+{
+	if (sched_feat(SCHEDTUNE_BOOST_HOLD_ALL))
+		return true;
+
+	return task_has_rt_policy(p);
+}
+
+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);
+
+	/* Update timeout on enqueue */
+	if (task_count > 0) {
+		u64 now = sched_clock_cpu(cpu);
+
+		if (schedtune_update_timestamp(p))
+			bg->group[idx].ts = now;
+
+		/* Boost group activation or deactivation on that RQ */
+		if (bg->group[idx].tasks == 1)
+			schedtune_cpu_update(cpu, now);
+	}
+
+	trace_sched_tune_tasks_update(p, cpu, tasks, idx,
+			bg->group[idx].boost, bg->boost_max,
+			bg->group[idx].ts);
+}
+
+/*
+ * 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;
+
+	/*
+	 * 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 rq_flags;
+	unsigned int cpu;
+	struct rq *rq;
+	int src_bg; /* Source boost group index */
+	int dst_bg; /* Destination boost group index */
+	int tasks;
+	u64 now;
+
+	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 = task_rq_lock(task, &rq_flags);
+
+		if (!task->on_rq) {
+			task_rq_unlock(rq, task, &rq_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);
+			task_rq_unlock(rq, task, &rq_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;
+
+		/* Update boost hold start for this group */
+		now = sched_clock_cpu(cpu);
+		bg->group[dst_bg].ts = now;
+
+		/* Force boost group re-evaluation at next boost check */
+		bg->boost_ts = now - SCHEDTUNE_BOOST_HOLD_NS;
+
+		raw_spin_unlock(&bg->lock);
+		task_rq_unlock(rq, task, &rq_flags);
+	}
+
+	return 0;
+}
+
+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;
+
+	/*
+	 * 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);
+}
+
+int schedtune_cpu_boost(int cpu)
+{
+	struct boost_groups *bg;
+	u64 now;
+
+	bg = &per_cpu(cpu_boost_groups, cpu);
+	now = sched_clock_cpu(cpu);
+
+	/* Check to see if we have a hold in effect */
+	if (schedtune_boost_timeout(now, bg->boost_ts))
+		schedtune_cpu_update(cpu, now);
+
+	return bg->boost_max;
+}
+
+int schedtune_task_boost(struct task_struct *p)
+{
+	struct schedtune *st;
+	int task_boost;
+
+	if (unlikely(!schedtune_initialized))
+		return 0;
+
+	/* 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;
+
+	if (unlikely(!schedtune_initialized))
+		return 0;
+
+	/* 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;
+}
+
+static int
+boost_write(struct cgroup_subsys_state *css, struct cftype *cft,
+	    s64 boost)
+{
+	struct schedtune *st = css_st(css);
+
+	if (boost < 0 || boost > 100)
+		return -EINVAL;
+
+	st->boost = boost;
+
+	/* Update CPU boost */
+	schedtune_boostgroup_update(st->idx, st->boost);
+
+	return 0;
+}
+
+static struct cftype files[] = {
+	{
+		.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;
+		bg->group[st->idx].ts = 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;
+	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,
+	.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;
+}
+
+/*
+ * Initialize the cgroup structures
+ */
+static int
+schedtune_init(void)
+{
+	schedtune_spc_rdiv = reciprocal_value(100);
+	schedtune_init_cgroups();
+	return 0;
+}
+postcore_initcall(schedtune_init);