Re: [PATCH] x86,sched: Fix sched_smt_power_savings totally broken
From: Peter Zijlstra <hidden>
Date: 2012-01-09 11:06:10
Also in:
lkml
On Mon, 2012-01-09 at 19:14 -0500, Youquan Song wrote:
Fine, I will base your suggestion to develop another patch soon.
quoted hunk ↗ jump to hunk
@@ -3923,6 +3923,10 @@ static inline void update_sg_lb_stats(structsched_domain *sd, SCHED_POWER_SCALE); if (!sgs->group_capacity) sgs->group_capacity = fix_small_capacity(sd, group); + + if (sched_smt_power_savings) + sgs->group_capacity *= 2;
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.