[PATCH v4] sched/fair: Remove SCHED_LOAD_SHIFT and SCHED_LOAD_SCALE

[Ingo Molnar <mingo@kernel.org>]

* Yuyang Du <yuyang.du@intel.com> wrote:

> After cleaning up the sched metrics, these two definitions that cause
> ambiguity are not needed any more. Use NICE_0_LOAD_SHIFT and NICE_0_LOAD
> instead (the names suggest clearly who they are).
> 
> Suggested-by: Ben Segall <bsegall@google.com>
> Signed-off-by: Yuyang Du <yuyang.du@intel.com>

Yeah, so this patch was a bit of a trainwreck:

 - it didn't build on 32-bit kernels

 - a stale SCHED_LOAD_SHIFT definition was left around

 - the title and th changelog lies actively: it's not a removal, but a complex
   combination of a rename, replace and removal ...

I've fixed that all with the patch below, but _please_ be more careful in the 
future when changing scheduler code, and please also read your changelogs and 
patch titles before sending them out to make sure the label matches contents.

I'll push it all out in tip:sched/core if it passes testing.

Thanks,

	Ingo

=======================>
>From 172895e6b5216eba3e0880460829a8baeefd55f3 Mon Sep 17 00:00:00 2001
From: Yuyang Du <yuyang.du@intel.com>
Date: Tue, 5 Apr 2016 12:12:27 +0800
Subject: [PATCH] sched/fair: Rename SCHED_LOAD_SHIFT to NICE_0_LOAD_SHIFT and remove SCHED_LOAD_SCALE

After cleaning up the sched metrics, there are two definitions that are
ambiguous and confusing: SCHED_LOAD_SHIFT and SCHED_LOAD_SHIFT.

Resolve this:

 - Rename SCHED_LOAD_SHIFT to NICE_0_LOAD_SHIFT, which better reflects what
   it is.

 - Replace SCHED_LOAD_SCALE use with SCHED_CAPACITY_SCALE and remove SCHED_LOAD_SCALE.

Suggested-by: Ben Segall <bsegall@google.com>
Signed-off-by: Yuyang Du <yuyang.du@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dietmar.eggemann@arm.com
Cc: lizefan@huawei.com
Cc: morten.rasmussen@arm.com
Cc: pjt@google.com
Cc: umgwanakikbuti@gmail.com
Cc: vincent.guittot@linaro.org
Link: http://lkml.kernel.org/r/1459829551-21625-3-git-send-email-yuyang.du@intel.com
[ Rewrote the changelog and fixed the build on 32-bit kernels. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/sched/fair.c  |  4 ++--
 kernel/sched/sched.h | 22 +++++++++++-----------
 2 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 76ca86e9fc20..e1485710d1ec 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -719,7 +719,7 @@ void post_init_entity_util_avg(struct sched_entity *se)
 {
 	struct cfs_rq *cfs_rq = cfs_rq_of(se);
 	struct sched_avg *sa = &se->avg;
-	long cap = (long)(scale_load_down(SCHED_LOAD_SCALE) - cfs_rq->avg.util_avg) / 2;
+	long cap = (long)(SCHED_CAPACITY_SCALE - cfs_rq->avg.util_avg) / 2;
 
 	if (cap > 0) {
 		if (cfs_rq->avg.util_avg != 0) {
@@ -7010,7 +7010,7 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
 	if (busiest->group_type == group_overloaded &&
 	    local->group_type   == group_overloaded) {
 		load_above_capacity = busiest->sum_nr_running *
-					SCHED_LOAD_SCALE;
+				      scale_load_down(NICE_0_LOAD);
 		if (load_above_capacity > busiest->group_capacity)
 			load_above_capacity -= busiest->group_capacity;
 		else
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index ad83361f9e67..d24e91b0a722 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -56,25 +56,25 @@ static inline void cpu_load_update_active(struct rq *this_rq) { }
  * increase coverage and consistency always enable it on 64bit platforms.
  */
 #ifdef CONFIG_64BIT
-# define SCHED_LOAD_SHIFT	(SCHED_FIXEDPOINT_SHIFT + SCHED_FIXEDPOINT_SHIFT)
+# 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)
 #else
-# define SCHED_LOAD_SHIFT	(SCHED_FIXEDPOINT_SHIFT)
+# define NICE_0_LOAD_SHIFT	(SCHED_FIXEDPOINT_SHIFT)
 # define scale_load(w)		(w)
 # define scale_load_down(w)	(w)
 #endif
 
-#define SCHED_LOAD_SCALE	(1L << SCHED_LOAD_SHIFT)
-
 /*
- * NICE_0's weight (visible to users) and its load (invisible to users) have
- * independent ranges, but they should be well calibrated. We use scale_load()
- * and scale_load_down(w) to convert between them, and the following must be true:
- * scale_load(sched_prio_to_weight[20]) == NICE_0_LOAD
+ * 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
+ *
  */
-#define NICE_0_LOAD		SCHED_LOAD_SCALE
-#define NICE_0_SHIFT		SCHED_LOAD_SHIFT
+#define NICE_0_LOAD		(1L << NICE_0_LOAD_SHIFT)
 
 /*
  * Single value that decides SCHED_DEADLINE internal math precision.
@@ -863,7 +863,7 @@ DECLARE_PER_CPU(struct sched_domain *, sd_asym);
 struct sched_group_capacity {
 	atomic_t ref;
 	/*
-	 * CPU capacity of this group, SCHED_LOAD_SCALE being max capacity
+	 * CPU capacity of this group, SCHED_CAPACITY_SCALE being max capacity
 	 * for a single CPU.
 	 */
 	unsigned int capacity;