Re: [PATCH v3 09/21] sched/cache: Count tasks prefering destination LLC in a sched group

[Chen, Yu C]

On 2/20/2026 9:43 PM, Peter Zijlstra wrote:
> On Fri, Feb 20, 2026 at 01:52:48PM +0100, Peter Zijlstra wrote:
> > On Tue, Feb 10, 2026 at 02:18:49PM -0800, Tim Chen wrote:
> >
> > > @@ -11034,6 +11037,9 @@ static inline void update_sg_lb_stats(struct lb_env *env,
> > >   {
> > >   	int i, nr_running, local_group, sd_flags = env->sd->flags;
> > >   	bool balancing_at_rd = !env->sd->parent;
> > > +#ifdef CONFIG_SCHED_CACHE
> > > +	int dst_llc = llc_id(env->dst_cpu);
> > > +#endif
> > >   
> > >   	memset(sgs, 0, sizeof(*sgs));
> > >   
> > > @@ -11054,6 +11060,15 @@ static inline void update_sg_lb_stats(struct lb_env *env,
> > >   		if (cpu_overutilized(i))
> > >   			*sg_overutilized = 1;
> > >   
> > > +#ifdef CONFIG_SCHED_CACHE
> > > +		if (sched_cache_enabled() && llc_id(i) != dst_llc) {
> >
> > If you write that like:
> >
> > 		if (sched_cache_enabled && llc_id(i) != llc_id(env->dst_cpu))
> >
> > You can get rid of that dst_llc variable, but more importantly its
> > ifdeffery.
>
> Ah, you're perhaps wanting to not re-load on the dst_llc usage below?

Yes.

> Do the compilers DTRT when you mark llc_id() as __pure?

OK, we will have a try on this.

thanks,
Chenyu