Re: [PATCH v3 03/21] sched/cache: Introduce helper functions to enforce LLC migration policy

[Chen, Yu C]

Hi Peter,

On 2/19/2026 7:29 PM, Peter Zijlstra wrote:
> On Tue, Feb 10, 2026 at 02:18:43PM -0800, Tim Chen wrote:
>
> > +/*
> > + * The margin used when comparing utilization.
> > + * is 'util1' noticeably greater than 'util2'
> > + * Derived from capacity_greater().
> > + * Bias is in perentage.
> > + */
> > +/* Allows dst util to be bigger than src util by up to bias percent */
> > +#define util_greater(util1, util2) \
> > +	((util1) * 100 > (util2) * 120)
>
> > + * 20% is the utilization imbalance percentage to decide
> > + * if the preferred LLC is busier than the non-preferred LLC.
> > + * 20 is a little higher than the LLC domain's imbalance_pct
> > + * 17. The hysteresis is used to avoid task bouncing between the
> > + * preferred LLC and the non-preferred LLC.
>
> So not saying this needs changing now, but consider that imbalance_pct
> can be changed through debugfs. Do you want this 120 to be expressed in
> terms of imbalance_pct rather than being hardcoded?

Got it, I will look into adding a margin to imbalance_pct for this
comparison. With this  change, I assume we can remove the llc_imb_pct
debugfs entry in patch 19.

thanks,
Chenyu
> Anyway, let me read on..