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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2008-06-27 13:41:28 +0200
committerIngo Molnar <mingo@elte.hu>2008-06-27 14:31:40 +0200
commit408ed066b11cf9ee4536573b4269ee3613bd735e (patch)
tree3b1367dafc96835c2fcbf289a7af808eb2efa605
parentsched: hierarchical load vs affine wakeups (diff)
downloadlinux-408ed066b11cf9ee4536573b4269ee3613bd735e.tar.xz
linux-408ed066b11cf9ee4536573b4269ee3613bd735e.zip
sched: hierarchical load vs find_busiest_group
find_busiest_group() has some assumptions about task weight being in the NICE_0_LOAD range. Hierarchical task groups break this assumption - fix this by replacing it with the average task weight, which will adapt the situation. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> Cc: Mike Galbraith <efault@gmx.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--kernel/sched.c26
1 files changed, 23 insertions, 3 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index 6a6b0139eb32..5e2aa394a812 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3050,6 +3050,7 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
max_load = this_load = total_load = total_pwr = 0;
busiest_load_per_task = busiest_nr_running = 0;
this_load_per_task = this_nr_running = 0;
+
if (idle == CPU_NOT_IDLE)
load_idx = sd->busy_idx;
else if (idle == CPU_NEWLY_IDLE)
@@ -3064,6 +3065,8 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
int __group_imb = 0;
unsigned int balance_cpu = -1, first_idle_cpu = 0;
unsigned long sum_nr_running, sum_weighted_load;
+ unsigned long sum_avg_load_per_task;
+ unsigned long avg_load_per_task;
local_group = cpu_isset(this_cpu, group->cpumask);
@@ -3072,6 +3075,8 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
/* Tally up the load of all CPUs in the group */
sum_weighted_load = sum_nr_running = avg_load = 0;
+ sum_avg_load_per_task = avg_load_per_task = 0;
+
max_cpu_load = 0;
min_cpu_load = ~0UL;
@@ -3105,6 +3110,8 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
avg_load += load;
sum_nr_running += rq->nr_running;
sum_weighted_load += weighted_cpuload(i);
+
+ sum_avg_load_per_task += cpu_avg_load_per_task(i);
}
/*
@@ -3126,7 +3133,20 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
avg_load = sg_div_cpu_power(group,
avg_load * SCHED_LOAD_SCALE);
- if ((max_cpu_load - min_cpu_load) > SCHED_LOAD_SCALE)
+
+ /*
+ * Consider the group unbalanced when the imbalance is larger
+ * than the average weight of two tasks.
+ *
+ * APZ: with cgroup the avg task weight can vary wildly and
+ * might not be a suitable number - should we keep a
+ * normalized nr_running number somewhere that negates
+ * the hierarchy?
+ */
+ avg_load_per_task = sg_div_cpu_power(group,
+ sum_avg_load_per_task * SCHED_LOAD_SCALE);
+
+ if ((max_cpu_load - min_cpu_load) > 2*avg_load_per_task)
__group_imb = 1;
group_capacity = group->__cpu_power / SCHED_LOAD_SCALE;
@@ -3267,9 +3287,9 @@ small_imbalance:
if (busiest_load_per_task > this_load_per_task)
imbn = 1;
} else
- this_load_per_task = SCHED_LOAD_SCALE;
+ this_load_per_task = cpu_avg_load_per_task(this_cpu);
- if (max_load - this_load + SCHED_LOAD_SCALE_FUZZ >=
+ if (max_load - this_load + 2*busiest_load_per_task >=
busiest_load_per_task * imbn) {
*imbalance = busiest_load_per_task;
return busiest;