[PATCH 1/2] sched: cpufreq: ignore SMT when determining max cpu capacity

Steve Muckle
2016-08-26T18:41:53Z

PELT does not consider SMT when scaling its utilization values via
arch_scale_cpu_capacity(). The value in rq->cpu_capacity_orig does
take SMT into consideration though and therefore may be smaller than
the utilization reported by PELT.

On an Intel i7-3630QM for example rq->cpu_capacity_orig is 589 but
util_avg scales up to 1024. This means that a 50% utilized CPU will show
up in schedutil as ~86% busy.

Fix this by using the same CPU scaling value in schedutil as that which
is used by PELT.

Signed-off-by: Steve Muckle <smuckle@linaro.org>
---
kernel/sched/cpufreq_schedutil.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 60d985f4dc47..cb8a77b1ef1b 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -147,7 +147,9 @@ static unsigned int get_next_freq(struct sugov_cpu *sg_cpu, unsigned long util,
static void sugov_get_util(unsigned long *util, unsigned long *max)
{
struct rq *rq = this_rq();
- unsigned long cfs_max = rq->cpu_capacity_orig;
+ unsigned long cfs_max;
+
+ cfs_max = arch_scale_cpu_capacity(NULL, smp_processor_id());

*util = min(rq->cfs.avg.util_avg, cfs_max);
*max = cfs_max;
--
2.7.3