From: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Don't pull tasks from a group if that would cause the group's total load to
drop below its total cpu_power (ie. cause the group to start going idle).
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
kernel/sched.c | 9 +++++++--
1 files changed, 7 insertions(+), 2 deletions(-)
diff -puN kernel/sched.c~sched-allow-the-load-to-grow-upto-its-cpu_power kernel/sched.c
--- devel/kernel/sched.c~sched-allow-the-load-to-grow-upto-its-cpu_power 2005-09-07 20:11:04.000000000 -0700
+++ devel-akpm/kernel/sched.c 2005-09-07 20:11:04.000000000 -0700
@@ -2009,6 +2009,7 @@ find_busiest_group(struct sched_domain *
{
struct sched_group *busiest = NULL, *this = NULL, *group = sd->groups;
unsigned long max_load, avg_load, total_load, this_load, total_pwr;
+ unsigned long max_pull;
int load_idx;
max_load = this_load = total_load = total_pwr = 0;
@@ -2058,7 +2059,7 @@ find_busiest_group(struct sched_domain *
group = group->next;
} while (group != sd->groups);
- if (!busiest || this_load >= max_load)
+ if (!busiest || this_load >= max_load || max_load <= SCHED_LOAD_SCALE)
goto out_balanced;
avg_load = (SCHED_LOAD_SCALE * total_load) / total_pwr;
@@ -2078,8 +2079,12 @@ find_busiest_group(struct sched_domain *
* by pulling tasks to us. Be careful of negative numbers as they'll
* appear as very large values with unsigned longs.
*/
+
+ /* Don't want to pull so many tasks that a group would go idle */
+ max_pull = min(max_load - avg_load, max_load - SCHED_LOAD_SCALE);
+
/* How much load to actually move to equalise the imbalance */
- *imbalance = min((max_load - avg_load) * busiest->cpu_power,
+ *imbalance = min(max_pull * busiest->cpu_power,
(avg_load - this_load) * this->cpu_power)
/ SCHED_LOAD_SCALE;
_