When calculating capacity we use the following calculation:
capacity = DIV_ROUND_CLOSEST(power, SCHED_LOAD_SCALE);
In SMT2, power will be 1178/2 (provided we are not scaling power with
freq say) and SCHED_LOAD_SCALE will be 1024, resulting in capacity
being 1.
With SMT4 however, power will be 1178/4, hence capacity will end up as
0.
Fix this by ensuring capacity is always at least 1 after this
calculation.
Signed-off-by: Michael Neuling <mi...@neuling.org>
---
I'm not sure this is the correct fix but this works for me.
Original post here:
http://lkml.org/lkml/2010/3/30/884
---
kernel/sched_fair.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
Index: linux-2.6-ozlabs/kernel/sched_fair.c
===================================================================
--- linux-2.6-ozlabs.orig/kernel/sched_fair.c
+++ linux-2.6-ozlabs/kernel/sched_fair.c
@@ -1482,6 +1482,7 @@ static int select_task_rq_fair(struct ta
}
capacity = DIV_ROUND_CLOSEST(power, SCHED_LOAD_SCALE);
+ capacity = max(capacity, 1UL);
if (tmp->flags & SD_POWERSAVINGS_BALANCE)
nr_running /= 2;
@@ -2488,6 +2489,7 @@ static inline void update_sg_lb_stats(st
sgs->group_capacity =
DIV_ROUND_CLOSEST(group->cpu_power, SCHED_LOAD_SCALE);
+ sgs->group_capacity = max(sgs->group_capacity, 1UL);
}
/**
@@ -2795,9 +2797,11 @@ find_busiest_queue(struct sched_group *g
for_each_cpu(i, sched_group_cpus(group)) {
unsigned long power = power_of(i);
- unsigned long capacity = DIV_ROUND_CLOSEST(power,
SCHED_LOAD_SCALE);
+ unsigned long capacity;
unsigned long wl;
+ capacity = max(DIV_ROUND_CLOSEST(power, SCHED_LOAD_SCALE), 1UL);
+
if (!cpumask_test_cpu(i, cpus))
continue;
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev
