Re: [PATCH] x86,sched: Fix sched_smt_power_savings totally broken

[Youquan Song <youquan.song@intel.com>]

> Note, this has the hard-coded assumption you only have 2 threads per
> core, which while true for intel, isn't true in general. I think you
> meant to write *= group->group_weight or somesuch.
> 
> Also, you forgot to limit this to the SD_SHARE_CPUPOWER domain, you're
> now doubling the capacity for all domains.
> 
> Furthermore, have a look at the SD_PREFER_SIBLING logic and make sure
> you're not fighting that.
> 
Thanks Peter! Here is the patch. 

-Youquan

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a4d2b7a..4ada3e7 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3923,6 +3923,10 @@ static inline void update_sg_lb_stats(struct
sched_domain *sd,
                                                SCHED_POWER_SCALE);
        if (!sgs->group_capacity)
                sgs->group_capacity = fix_small_capacity(sd, group);
+
+       if (sched_smt_power_savings && !(sd->flags & SD_SHARE_CPUPOWER))
+               sgs->group_capacity = group->group_weight;
+
        sgs->group_weight = group->group_weight;

        if (sgs->group_capacity > sgs->sum_nr_running)