Hi Steve, On 19/08/16 02:55, Steve Muckle wrote: > 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 <smuc...@linaro.org> > --- > kernel/sched/fair.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > 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);
Wouldn't you have to subscribe to this rcu pointer rq->sd w/ something like 'rcu_dereference(cpu_rq(cpu)->sd)'? IMHO, __update_load_avg() is called outside existing RCU read-side critical sections as well so there would be a pair of rcu_read_lock()/rcu_read_unlock() required in this case. > > /* delta_w is the amount already accumulated against our next period */ > delta_w = sa->period_contrib; >
