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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2008-04-19 19:45:00 +0200
committerIngo Molnar <mingo@elte.hu>2008-04-19 19:45:00 +0200
commit8f1bc385cfbab474db6c27b5af1e439614f3025c (patch)
treee4cfb8255d62621d17bc08ee5f94f42a0cc22677 /kernel
parent4a55bd5e97b1775913f88f11108a4f144f590e89 (diff)
downloadlinux-stericsson-8f1bc385cfbab474db6c27b5af1e439614f3025c.tar.gz
sched: fair: weight calculations
In order to level the hierarchy, we need to calculate load based on the root view. That is, each task's load is in the same unit. A / \ B 1 / \ 2 3 To compute 1's load we do: weight(1) -------------- rq_weight(A) To compute 2's load we do: weight(2) weight(B) ------------ * ----------- rq_weight(B) rw_weight(A) This yields load fractions in comparable units. The consequence is that it changes virtual time. We used to have: time_{i} vtime_{i} = ------------ weight_{i} vtime = \Sum vtime_{i} = time / rq_weight. But with the new way of load calculation we get that vtime equals time. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sched.c9
-rw-r--r--kernel/sched_fair.c95
2 files changed, 65 insertions, 39 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index 3202462109f5..6d55dfc56cab 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1320,6 +1320,9 @@ static void __resched_task(struct task_struct *p, int tif_bit)
*/
#define SRR(x, y) (((x) + (1UL << ((y) - 1))) >> (y))
+/*
+ * delta *= weight / lw
+ */
static unsigned long
calc_delta_mine(unsigned long delta_exec, unsigned long weight,
struct load_weight *lw)
@@ -1342,12 +1345,6 @@ calc_delta_mine(unsigned long delta_exec, unsigned long weight,
return (unsigned long)min(tmp, (u64)(unsigned long)LONG_MAX);
}
-static inline unsigned long
-calc_delta_fair(unsigned long delta_exec, struct load_weight *lw)
-{
- return calc_delta_mine(delta_exec, NICE_0_LOAD, lw);
-}
-
static inline void update_load_add(struct load_weight *lw, unsigned long inc)
{
lw->weight += inc;
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index ed8ce329899b..d72e8b41b3e4 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -334,6 +334,34 @@ int sched_nr_latency_handler(struct ctl_table *table, int write,
#endif
/*
+ * delta *= w / rw
+ */
+static inline unsigned long
+calc_delta_weight(unsigned long delta, struct sched_entity *se)
+{
+ for_each_sched_entity(se) {
+ delta = calc_delta_mine(delta,
+ se->load.weight, &cfs_rq_of(se)->load);
+ }
+
+ return delta;
+}
+
+/*
+ * delta *= rw / w
+ */
+static inline unsigned long
+calc_delta_fair(unsigned long delta, struct sched_entity *se)
+{
+ for_each_sched_entity(se) {
+ delta = calc_delta_mine(delta,
+ cfs_rq_of(se)->load.weight, &se->load);
+ }
+
+ return delta;
+}
+
+/*
* The idea is to set a period in which each task runs once.
*
* When there are too many tasks (sysctl_sched_nr_latency) we have to stretch
@@ -362,47 +390,54 @@ static u64 __sched_period(unsigned long nr_running)
*/
static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
- u64 slice = __sched_period(cfs_rq->nr_running);
-
- for_each_sched_entity(se) {
- cfs_rq = cfs_rq_of(se);
-
- slice *= se->load.weight;
- do_div(slice, cfs_rq->load.weight);
- }
-
-
- return slice;
+ return calc_delta_weight(__sched_period(cfs_rq->nr_running), se);
}
/*
* We calculate the vruntime slice of a to be inserted task
*
- * vs = s/w = p/rw
+ * vs = s*rw/w = p
*/
static u64 sched_vslice_add(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
unsigned long nr_running = cfs_rq->nr_running;
- unsigned long weight;
- u64 vslice;
if (!se->on_rq)
nr_running++;
- vslice = __sched_period(nr_running);
+ return __sched_period(nr_running);
+}
+
+/*
+ * The goal of calc_delta_asym() is to be asymmetrically around NICE_0_LOAD, in
+ * that it favours >=0 over <0.
+ *
+ * -20 |
+ * |
+ * 0 --------+-------
+ * .'
+ * 19 .'
+ *
+ */
+static unsigned long
+calc_delta_asym(unsigned long delta, struct sched_entity *se)
+{
+ struct load_weight lw = {
+ .weight = NICE_0_LOAD,
+ .inv_weight = 1UL << (WMULT_SHIFT-NICE_0_SHIFT)
+ };
for_each_sched_entity(se) {
- cfs_rq = cfs_rq_of(se);
+ struct load_weight *se_lw = &se->load;
- weight = cfs_rq->load.weight;
- if (!se->on_rq)
- weight += se->load.weight;
+ if (se->load.weight < NICE_0_LOAD)
+ se_lw = &lw;
- vslice *= NICE_0_LOAD;
- do_div(vslice, weight);
+ delta = calc_delta_mine(delta,
+ cfs_rq_of(se)->load.weight, se_lw);
}
- return vslice;
+ return delta;
}
/*
@@ -419,11 +454,7 @@ __update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
curr->sum_exec_runtime += delta_exec;
schedstat_add(cfs_rq, exec_clock, delta_exec);
- delta_exec_weighted = delta_exec;
- if (unlikely(curr->load.weight != NICE_0_LOAD)) {
- delta_exec_weighted = calc_delta_fair(delta_exec_weighted,
- &curr->load);
- }
+ delta_exec_weighted = calc_delta_fair(delta_exec, curr);
curr->vruntime += delta_exec_weighted;
}
@@ -632,8 +663,7 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
/* sleeps upto a single latency don't count. */
if (sched_feat(NEW_FAIR_SLEEPERS)) {
if (sched_feat(NORMALIZED_SLEEPER))
- vruntime -= calc_delta_fair(sysctl_sched_latency,
- &cfs_rq->load);
+ vruntime -= calc_delta_weight(sysctl_sched_latency, se);
else
vruntime -= sysctl_sched_latency;
}
@@ -1132,11 +1162,10 @@ static unsigned long wakeup_gran(struct sched_entity *se)
unsigned long gran = sysctl_sched_wakeup_granularity;
/*
- * More easily preempt - nice tasks, while not making
- * it harder for + nice tasks.
+ * More easily preempt - nice tasks, while not making it harder for
+ * + nice tasks.
*/
- if (unlikely(se->load.weight > NICE_0_LOAD))
- gran = calc_delta_fair(gran, &se->load);
+ gran = calc_delta_asym(sysctl_sched_wakeup_granularity, se);
return gran;
}