Re: [Patch v3 4/6] sched/fair: Consider the idle state of the whole core for load balance

[Tim Chen]

On Fri, 2023-07-14 at 18:32 +0530, Shrikanth Hegde wrote:
> 
> 
> 
> Tried on a symmetric system with all cores having SMT=4 as well. There was reduction in migrations here as well.
> Didnt observe any major regressions when microbenchmarks run alone. Such as hackbench, stress-ng. 
> 
> So. Here is tested-by. 
> Tested-by: Shrikanth Hegde <sshegde@xxxxxxxxxxxxxxxxxx>

Thanks for testing.  

> 
> 
> > +
> >  	/* Are we the first CPU of this group ? */
> >  	return group_balance_cpu(sg) == env->dst_cpu;
> >  }
> 
> One doubt though, Here a fully idle core would be chosen instead of first idle cpu in the 
> group (if there is one). Since coming out of idle of SMT is faster compared to a fully idle core,
> would latency increase? Or that concerns mainly wakeup path?

Yeah, I think that concern is for the wakeup path and not for the balance path.

Tim