Re: [PATCH RESEND] x86/smpboot: avoid SMT domain attach/destroy if SMT is not enabled

[Li Chen]

Hi Thomas,

 ---- On Fri, 20 Jun 2025 21:54:27 +0800  Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote --- 
 > On Tue, Apr 22 2025 at 16:47, Li Chen wrote:
 > > Currently, the SMT domain is added into sched_domain_topology
 > > by default if CONFIG_SCHED_SMT is enabled.
 > >
 > > If cpu_attach_domain finds that the CPU SMT domain’s cpumask_weight
 > > is just 1, it will destroy_sched_domain it.
 > 
 > If cpu_attach_domain() ..., it will destroy it.
 > 
 > > On a large machine, such as one with 512 cores, this results in
 > > 512 redundant domain attach/destroy operations.
 > >
 > > We can avoid these unnecessary operations by simply checking
 > 
 > s/We can avoid/Avoid/
 > 
 > > cpu_smt_num_threads and not inserting SMT domain into x86_topology if SMT
 > 
 > the SMT domain 
 > 
 > > is not enabled.
 > >
 > > #ifdef CONFIG_SCHED_SMT
 > > -    x86_topology[i++] = (struct sched_domain_topology_level){
 > > -        cpu_smt_mask, cpu_smt_flags, SD_INIT_NAME(SMT)
 > > -    };
 > > +    if (cpu_smt_num_threads > 1) {
 > > +        x86_topology[i++] = (struct sched_domain_topology_level){
 > > +            cpu_smt_mask, cpu_smt_flags, SD_INIT_NAME(SMT)
 > > +        };
 > > +    }
 > 
 > Looks about right, though I really detest this coding style. I'm not
 > blaming you, as you just followed the already existing bad taste...
 > 
 > Thanks,
 > 
 >         tglx
 > 

Thanks for your review, I have fixed the wording issues here: https://lore.kernel.org/all/20250624085559.69436-1-me@linux.beauty/T/#t

Regards,
Li