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Date:	Mon, 16 May 2016 02:59:34 +0800
From:	Yuyang Du <yuyang.du@...el.com>
To:	peterz@...radead.org, mingo@...nel.org,
	linux-kernel@...r.kernel.org
Cc:	bsegall@...gle.com, pjt@...gle.com, morten.rasmussen@....com,
	vincent.guittot@...aro.org, dietmar.eggemann@....com,
	juri.lelli@....com, Yuyang Du <yuyang.du@...el.com>
Subject: [RFC PATCH 9/9] sched/fair: Rename scale_load() and scale_load_down()

Rename scale_load() and scale_load_down() to user_to_kernel_load()
and kernel_to_user_load() respectively. This helps us tag them
clearly and avoid confusion.

Signed-off-by: Yuyang Du <yuyang.du@...el.com>
---
 kernel/sched/core.c  |    8 ++++----
 kernel/sched/fair.c  |   11 ++++++++---
 kernel/sched/sched.h |   16 ++++++++--------
 3 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 404c078..c4c84d4 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -735,12 +735,12 @@ static void set_load_weight(struct task_struct *p)
 	 * SCHED_IDLE tasks get minimal weight:
 	 */
 	if (idle_policy(p->policy)) {
-		load->weight = scale_load(WEIGHT_IDLEPRIO);
+		load->weight = user_to_kernel_load(WEIGHT_IDLEPRIO);
 		load->inv_weight = WMULT_IDLEPRIO;
 		return;
 	}
 
-	load->weight = scale_load(sched_prio_to_weight[prio]);
+	load->weight = user_to_kernel_load(sched_prio_to_weight[prio]);
 	load->inv_weight = sched_prio_to_wmult[prio];
 }
 
@@ -8216,7 +8216,7 @@ static void cpu_cgroup_attach(struct cgroup_taskset *tset)
 static int cpu_shares_write_u64(struct cgroup_subsys_state *css,
 				struct cftype *cftype, u64 shareval)
 {
-	return sched_group_set_shares(css_tg(css), scale_load(shareval));
+	return sched_group_set_shares(css_tg(css), user_to_kernel_load(shareval));
 }
 
 static u64 cpu_shares_read_u64(struct cgroup_subsys_state *css,
@@ -8224,7 +8224,7 @@ static u64 cpu_shares_read_u64(struct cgroup_subsys_state *css,
 {
 	struct task_group *tg = css_tg(css);
 
-	return (u64) scale_load_down(tg->shares);
+	return (u64) kernel_to_user_load(tg->shares);
 }
 
 #ifdef CONFIG_CFS_BANDWIDTH
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 88913b8..fbf6220 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -189,7 +189,7 @@ static void __update_inv_weight(struct load_weight *lw)
 	if (likely(lw->inv_weight))
 		return;
 
-	w = scale_load_down(lw->weight);
+	w = kernel_to_user_load(lw->weight);
 
 	if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
 		lw->inv_weight = 1;
@@ -210,10 +210,14 @@ static void __update_inv_weight(struct load_weight *lw)
  *
  * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
  * weight/lw.weight <= 1, and therefore our shift will also be positive.
+ *
+ * Note load.weight falls back to user load scale (i.e., NICE_0's load is
+ * 1024), instead of possibly increased kernel load scale (i.e., NICE_0's
+ * load is NICE_0_LOAD) due to multiplication and division efficiency.
  */
 static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
 {
-	u64 fact = scale_load_down(weight);
+	u64 fact = kernel_to_user_load(weight);
 	int shift = WMULT_SHIFT;
 
 	__update_inv_weight(lw);
@@ -8608,7 +8612,8 @@ int sched_group_set_shares(struct task_group *tg, unsigned long shares)
 	if (!tg->se[0])
 		return -EINVAL;
 
-	shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
+	shares = clamp(shares, user_to_kernel_load(MIN_SHARES),
+		       user_to_kernel_load(MAX_SHARES));
 
 	mutex_lock(&shares_mutex);
 	if (tg->shares == shares)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 3432985..0b8b3f3 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -57,22 +57,22 @@ static inline void cpu_load_update_active(struct rq *this_rq) { }
  */
 #ifdef CONFIG_64BIT
 # define NICE_0_LOAD_SHIFT	(SCHED_FIXEDPOINT_SHIFT + SCHED_FIXEDPOINT_SHIFT)
-# define scale_load(w)		((w) << SCHED_FIXEDPOINT_SHIFT)
-# define scale_load_down(w)	((w) >> SCHED_FIXEDPOINT_SHIFT)
+# define user_to_kernel_load(w)	((w) << SCHED_FIXEDPOINT_SHIFT)
+# define kernel_to_user_load(w)	((w) >> SCHED_FIXEDPOINT_SHIFT)
 #else
 # define NICE_0_LOAD_SHIFT	(SCHED_FIXEDPOINT_SHIFT)
-# define scale_load(w)		(w)
-# define scale_load_down(w)	(w)
+# define user_to_kernel_load(w)	(w)
+# define kernel_to_user_load(w)	(w)
 #endif
 
 /*
  * Task weight (visible to users) and its load (invisible to users) have
  * independent resolution, but they should be well calibrated. We use
- * scale_load() and scale_load_down(w) to convert between them. The
- * following must be true:
- *
- *  scale_load(sched_prio_to_weight[USER_PRIO(NICE_TO_PRIO(0))]) == NICE_0_LOAD
+ * user_to_kernel_load() and kernel_to_user_load(w) to convert between
+ * them. The following must be true:
  *
+ * user_to_kernel_load(sched_prio_to_weight[USER_PRIO(NICE_TO_PRIO(0))]) == NICE_0_LOAD
+ * kernel_to_user_load(NICE_0_LOAD) == sched_prio_to_weight[USER_PRIO(NICE_TO_PRIO(0))]
  */
 #define NICE_0_LOAD		(1L << NICE_0_LOAD_SHIFT)
 
-- 
1.7.9.5

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