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authorIngo Molnar <mingo@elte.hu>2007-10-15 17:00:03 +0200
committerIngo Molnar <mingo@elte.hu>2007-10-15 17:00:03 +0200
commita25707f3aef9cf68c341eba5960d580f364e4e6f (patch)
tree77f13a0d32f68217cf6be32b1ab755bf7c1c0665 /kernel/sched.c
parent8ebc91d93669af39dbed50914d7daf457eeb43be (diff)
sched: remove precise CPU load
CPU load calculations are statistical anyway, and there's little benefit from having it calculated on every scheduling event. So remove this code, it gets rid of a divide from the scheduler wakeup and context-switch fastpath. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Mike Galbraith <efault@gmx.de> Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/sched.c')
-rw-r--r--kernel/sched.c42
1 files changed, 7 insertions, 35 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index d4dabfcc776c..25cc9b2a8c15 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1972,42 +1972,11 @@ unsigned long nr_active(void)
*/
static void update_cpu_load(struct rq *this_rq)
{
- u64 fair_delta64, exec_delta64, idle_delta64, sample_interval64, tmp64;
unsigned long total_load = this_rq->ls.load.weight;
unsigned long this_load = total_load;
- struct load_stat *ls = &this_rq->ls;
int i, scale;
this_rq->nr_load_updates++;
- if (unlikely(!(sysctl_sched_features & SCHED_FEAT_PRECISE_CPU_LOAD)))
- goto do_avg;
-
- /* Update delta_fair/delta_exec fields first */
- update_curr_load(this_rq);
-
- fair_delta64 = ls->delta_fair + 1;
- ls->delta_fair = 0;
-
- exec_delta64 = ls->delta_exec + 1;
- ls->delta_exec = 0;
-
- sample_interval64 = this_rq->clock - ls->load_update_last;
- ls->load_update_last = this_rq->clock;
-
- if ((s64)sample_interval64 < (s64)TICK_NSEC)
- sample_interval64 = TICK_NSEC;
-
- if (exec_delta64 > sample_interval64)
- exec_delta64 = sample_interval64;
-
- idle_delta64 = sample_interval64 - exec_delta64;
-
- tmp64 = div64_64(SCHED_LOAD_SCALE * exec_delta64, fair_delta64);
- tmp64 = div64_64(tmp64 * exec_delta64, sample_interval64);
-
- this_load = (unsigned long)tmp64;
-
-do_avg:
/* Update our load: */
for (i = 0, scale = 1; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
@@ -2017,7 +1986,13 @@ do_avg:
old_load = this_rq->cpu_load[i];
new_load = this_load;
-
+ /*
+ * Round up the averaging division if load is increasing. This
+ * prevents us from getting stuck on 9 if the load is 10, for
+ * example.
+ */
+ if (new_load > old_load)
+ new_load += scale-1;
this_rq->cpu_load[i] = (old_load*(scale-1) + new_load) >> i;
}
}
@@ -6484,7 +6459,6 @@ static inline void init_cfs_rq(struct cfs_rq *cfs_rq, struct rq *rq)
void __init sched_init(void)
{
- u64 now = sched_clock();
int highest_cpu = 0;
int i, j;
@@ -6509,8 +6483,6 @@ void __init sched_init(void)
INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
list_add(&rq->cfs.leaf_cfs_rq_list, &rq->leaf_cfs_rq_list);
#endif
- rq->ls.load_update_last = now;
- rq->ls.load_update_start = now;
for (j = 0; j < CPU_LOAD_IDX_MAX; j++)
rq->cpu_load[j] = 0;