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Subject[RFC PATCH 9/9] sched/fair: Rename scale_load() and scale_load_down()
Date
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@intel.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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