Re: [PATCH v2 6/6 RFT] sched/fair: change sched asym checking condition

[Ricardo Neri]

On Thu, Feb 01, 2024 at 08:49:05PM +0530, Shrikanth Hegde wrote:
> 
> 
> On 2/1/24 5:10 PM, kuiliang Shi wrote:
> > 
> > 
> > On 2/1/24 9:10 AM, Ricardo Neri wrote:
> >> On Tue, Jan 30, 2024 at 09:17:08PM +0800, alexs@xxxxxxxxxx wrote:
> >>> From: Alex Shi <alexs@xxxxxxxxxx>
> >>>
> >>> Asym only used on SMT sd, or core sd with ITMT and core idled.
> >>> !sched_smt_active isn't necessary.
> >>
> >> sched_smt_active() is implemented as a static key. Thus, if SMT is not
> >> enabled, we can quickly return without having to check the rest of the
> >> conditions, as we should.
> > 
> > Hi Ricardo,
> > 
> > Thanks a lot for comments! I will drop this patch in this series.
> > 
> > But forgive my stupidity, asym feature is possible when SMT enabled instead of SMT disable. Why no SMT is a condition for asm feature? For this asym feature, I only see the SMT and MC domain use this, correct me if I'm wrong. 
> > 
> 
> on power7 ASYM_PACKING is used to pack at SMT level. 

Indeed, this is why the function returns true if it the sched domain has
the SD_SHARE_CPUCAPACITY flag.

When SMT is disabled there is no point in doing any check because we will
always want to use asym_packing.

> 
> On x86, ITMT topology uses ASYM_PACKING to do load balancing instead of using different cpu capacities.

You can look at x86_cluster_flags() and x86_die_flags().

> 
> Its possible to have it in PKG(earlier referred as DIE) as well. 
> In powerpc recently we did that for shared processor LPAR's. So asym feature is in PKG as well. 
> 
> >>
> >>>