[RFC PATCH 1/3] sched: Introduce structures necessary for WALT

[Vikram Mulukutla]

From: Srivatsa Vaddagiri <vatsa@xxxxxxxxxxxxxx>

Add the per-task and per-runqueue data structures that
will later be used by Window Assisted Load Tracking (WALT)
to estimate task demand and CPU utilization.

Move cap_scale into sched.h as that will be needed by WALT
as well to implement frequency and capacity invariance.

Signed-off-by: Srivatsa Vaddagiri <vatsa@xxxxxxxxxxxxxx>
Signed-off-by: Vikram Mulukutla <markivx@xxxxxxxxxxxxxx>
---
 include/linux/sched.h | 39 +++++++++++++++++++++++++++++++++++++++
 kernel/sched/fair.c   |  2 --
 kernel/sched/sched.h  |  8 ++++++++
 3 files changed, 47 insertions(+), 2 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 62c68e5..64f8bec 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -315,6 +315,21 @@ extern char ___assert_task_state[1 - 2*!!(
 /* Task command name length */
 #define TASK_COMM_LEN 16
 
+/*
+ * These events may be replaced with a combination of existing scheduler flags
+ * provided that that doesn't make the implementation too fragile.
+ */
+enum task_event {
+	PUT_PREV_TASK   = 0,
+	PICK_NEXT_TASK  = 1,
+	TASK_WAKE       = 2,
+	TASK_MIGRATE    = 3,
+	TASK_UPDATE     = 4,
+	IRQ_UPDATE      = 5,
+};
+
+extern char *task_event_names[];
+
 #include <linux/spinlock.h>
 
 /*
@@ -1320,6 +1335,25 @@ struct sched_statistics {
 };
 #endif
 
+#ifdef CONFIG_SCHED_WALT
+
+/* ravg represents capacity scaled cpu-usage of tasks */
+struct ravg {
+	/*
+	 * 'mark_start' marks the most recent event for a task
+	 *
+	 * 'curr_window' represents task's cpu usage in its most recent
+	 * window
+	 *
+	 * 'prev_window' represents task's cpu usage in the window prior
+	 * to the one represented by 'curr_window'
+	*/
+	u64 mark_start;
+	u32 curr_window, prev_window;
+};
+#endif
+
+
 struct sched_entity {
 	struct load_weight	load;		/* for load-balancing */
 	struct rb_node		run_node;
@@ -1480,6 +1514,11 @@ struct task_struct {
 	const struct sched_class *sched_class;
 	struct sched_entity se;
 	struct sched_rt_entity rt;
+
+#ifdef CONFIG_SCHED_WALT
+	struct ravg ravg;
+#endif
+
 #ifdef CONFIG_CGROUP_SCHED
 	struct task_group *sched_task_group;
 #endif
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index ce8b244..39c826d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2674,8 +2674,6 @@ static u32 __compute_runnable_contrib(u64 n)
 	return contrib + runnable_avg_yN_sum[n];
 }
 
-#define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
-
 /*
  * We can represent the historical contribution to runnable average as the
  * coefficients of a geometric series.  To do this we sub-divide our runnable
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index c64fc51..9bf6925 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -65,6 +65,8 @@ static inline void cpu_load_update_active(struct rq *this_rq) { }
 # define scale_load_down(w)	(w)
 #endif
 
+#define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
+
 /*
  * Task weight (visible to users) and its load (invisible to users) have
  * independent resolution, but they should be well calibrated. We use
@@ -664,6 +666,12 @@ struct rq {
 	u64 max_idle_balance_cost;
 #endif
 
+#ifdef CONFIG_SCHED_WALT
+	u64 window_start;
+	u64 curr_runnable_sum;
+	u64 prev_runnable_sum;
+#endif /* CONFIG_SCHED_WALT */
+
 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
 	u64 prev_irq_time;
 #endif
-- 
TheMan