This is a note to let you know that I've just added the patch titled
sched: Set group_imb only a task can be pulled from the busiest cpu
to the 2.6.32-longterm tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/longterm/longterm-queue-2.6.32.git;a=summary
The filename of the patch is:
0010-sched-Set-group_imb-only-a-task-can-be-pulled-from-t.patch
and it can be found in the queue-2.6.32 subdirectory.
If you, or anyone else, feels it should not be added to the 2.6.32 longterm
tree,
please let <[email protected]> know about it.
>From aa6b0fe40bc1d36f3a98b7cb2e1f01bfc4ba40c3 Mon Sep 17 00:00:00 2001
From: Nikhil Rao <[email protected]>
Date: Thu, 10 Feb 2011 10:23:25 +0100
Subject: sched: Set group_imb only a task can be pulled from the busiest cpu
Commit: 2582f0eba54066b5e98ff2b27ef0cfa833b59f54 upstream
When cycling through sched groups to determine the busiest group, set
group_imb only if the busiest cpu has more than 1 runnable task. This patch
fixes the case where two cpus in a group have one runnable task each, but there
is a large weight differential between these two tasks. The load balancer is
unable to migrate any task from this group, and hence do not consider this
group to be imbalanced.
Signed-off-by: Nikhil Rao <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
LKML-Reference: <[email protected]>
[ small code readability edits ]
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Mike Galbraith <[email protected]>
Acked-by: Peter Zijlstra <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
kernel/sched.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3745,7 +3745,7 @@ static inline void update_sg_lb_stats(st
int local_group, const struct cpumask *cpus,
int *balance, struct sg_lb_stats *sgs)
{
- unsigned long load, max_cpu_load, min_cpu_load;
+ unsigned long load, max_cpu_load, min_cpu_load, max_nr_running;
int i;
unsigned int balance_cpu = -1, first_idle_cpu = 0;
unsigned long avg_load_per_task = 0;
@@ -3759,6 +3759,7 @@ static inline void update_sg_lb_stats(st
/* Tally up the load of all CPUs in the group */
max_cpu_load = 0;
min_cpu_load = ~0UL;
+ max_nr_running = 0;
for_each_cpu_and(i, sched_group_cpus(group), cpus) {
struct rq *rq = cpu_rq(i);
@@ -3776,8 +3777,10 @@ static inline void update_sg_lb_stats(st
load = target_load(i, load_idx);
} else {
load = source_load(i, load_idx);
- if (load > max_cpu_load)
+ if (load > max_cpu_load) {
max_cpu_load = load;
+ max_nr_running = rq->nr_running;
+ }
if (min_cpu_load > load)
min_cpu_load = load;
}
@@ -3815,11 +3818,10 @@ static inline void update_sg_lb_stats(st
if (sgs->sum_nr_running)
avg_load_per_task = sgs->sum_weighted_load /
sgs->sum_nr_running;
- if ((max_cpu_load - min_cpu_load) > 2*avg_load_per_task)
+ if ((max_cpu_load - min_cpu_load) > 2*avg_load_per_task &&
max_nr_running > 1)
sgs->group_imb = 1;
- sgs->group_capacity =
- DIV_ROUND_CLOSEST(group->cpu_power, SCHED_LOAD_SCALE);
+ sgs->group_capacity = DIV_ROUND_CLOSEST(group->cpu_power,
SCHED_LOAD_SCALE);
}
/**
Patches currently in longterm-queue-2.6.32 which might be from [email protected]
are
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