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authorVincent Guittot <vincent.guittot@linaro.org>2011-10-21 09:02:47 +0200
committerVincent Guittot <vincent.guittot@linaro.org>2011-11-14 11:09:38 +0100
commitd78f58161a7f5bbf304955bc01b455110578b9bc (patch)
treec5cef1778242aff2ef4399b042453a52bdf130d8
parentc2fdcfc81097255816194a584e6faabd3914cfc5 (diff)
downloadlinux-linaro-precise-d78f58161a7f5bbf304955bc01b455110578b9bc.tar.gz
sched: Ensure cpu_power periodic update
With a lot of small task, the softirq sched is nearly never called when no_hz is enable. Te load_balance is mainly called with the newly_idle mode which doesn't update the cpu_power. Add a next_update field which ensure a maximum update period when there is short activity Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
-rw-r--r--include/linux/sched.h1
-rw-r--r--kernel/sched_fair.c24
2 files changed, 17 insertions, 8 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 41d0237fd44..8610921984b 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -901,6 +901,7 @@ struct sched_group_power {
* single CPU.
*/
unsigned int power, power_orig;
+ unsigned long next_update;
};
struct sched_group {
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index bc8ee999381..320b7a05ef9 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -91,6 +91,8 @@ unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;
static const struct sched_class fair_sched_class;
+static unsigned long __read_mostly max_load_balance_interval = HZ/10;
+
/**************************************************************
* CFS operations on generic schedulable entities:
*/
@@ -2667,6 +2669,11 @@ static void update_group_power(struct sched_domain *sd, int cpu)
struct sched_domain *child = sd->child;
struct sched_group *group, *sdg = sd->groups;
unsigned long power;
+ unsigned long interval;
+
+ interval = msecs_to_jiffies(sd->balance_interval);
+ interval = clamp(interval, 1UL, max_load_balance_interval);
+ sdg->sgp->next_update = jiffies + interval;
if (!child) {
update_cpu_power(sd, cpu);
@@ -2774,12 +2781,15 @@ static inline void update_sg_lb_stats(struct sched_domain *sd,
* domains. In the newly idle case, we will allow all the cpu's
* to do the newly idle load balance.
*/
- if (idle != CPU_NEWLY_IDLE && local_group) {
- if (balance_cpu != this_cpu) {
- *balance = 0;
- return;
- }
- update_group_power(sd, this_cpu);
+ if (local_group) {
+ if (idle != CPU_NEWLY_IDLE) {
+ if (balance_cpu != this_cpu) {
+ *balance = 0;
+ return;
+ }
+ update_group_power(sd, this_cpu);
+ } else if (time_after_eq(jiffies, group->sgp->next_update))
+ update_group_power(sd, this_cpu);
}
/* Adjust by relative CPU power of the group */
@@ -3879,8 +3889,6 @@ void select_nohz_load_balancer(int stop_tick)
static DEFINE_SPINLOCK(balancing);
-static unsigned long __read_mostly max_load_balance_interval = HZ/10;
-
/*
* Scale the max load_balance interval with the number of CPUs in the system.
* This trades load-balance latency on larger machines for less cross talk.