| Message ID | 1471571741-19504-1-git-send-email-smuckle@linaro.org |
|---|---|
| State | New |
| Headers | show |
On Fri, Aug 19, 2016 at 10:30:36AM +0800, Wanpeng Li wrote: > 2016-08-19 9:55 GMT+08:00 Steve Muckle <steve.muckle@linaro.org>: > > PELT scales its util_sum and util_avg values via > > arch_scale_cpu_capacity(). If that function is passed the CPU's sched > > domain then it will reduce the scaling capacity if SD_SHARE_CPUCAPACITY > > is set. PELT does not pass in the sd however. The other caller of > > arch_scale_cpu_capacity, update_cpu_capacity(), does. This means > > util_sum and util_avg scale beyond the CPU capacity on SMT. > > > > On an Intel i7-3630QM for example rq->cpu_capacity_orig is 589 but > > util_avg scales up to 1024. > > > > Fix this by passing in the sd in __update_load_avg() as well. > > I believe we notice this at least several months ago. > https://lkml.org/lkml/2016/5/25/228 Glad to see I'm not alone in thinking this is an issue. It causes an issue with schedutil, effectively doubling the apparent demand on SMT. I don't know the load balance code well enough offhand to say whether it's an issue there. cheers, Steve
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 61d485421bed..95d34b337152 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2731,7 +2731,7 @@ __update_load_avg(u64 now, int cpu, struct sched_avg *sa, sa->last_update_time = now; scale_freq = arch_scale_freq_capacity(NULL, cpu); - scale_cpu = arch_scale_cpu_capacity(NULL, cpu); + scale_cpu = arch_scale_cpu_capacity(cpu_rq(cpu)->sd, cpu); /* delta_w is the amount already accumulated against our next period */ delta_w = sa->period_contrib;
PELT scales its util_sum and util_avg values via arch_scale_cpu_capacity(). If that function is passed the CPU's sched domain then it will reduce the scaling capacity if SD_SHARE_CPUCAPACITY is set. PELT does not pass in the sd however. The other caller of arch_scale_cpu_capacity, update_cpu_capacity(), does. This means util_sum and util_avg scale beyond the CPU capacity on SMT. On an Intel i7-3630QM for example rq->cpu_capacity_orig is 589 but util_avg scales up to 1024. Fix this by passing in the sd in __update_load_avg() as well. Signed-off-by: Steve Muckle <smuckle@linaro.org> --- kernel/sched/fair.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) -- 2.7.3