Messages in this thread Patch in this message | | | From | Michael Neuling <> | Date | Fri, 09 Apr 2010 16:21:18 +1000 | Subject | [PATCH 1/5] sched: fix capacity calculations for SMT4 |
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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 <mikey@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
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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;
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