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

[Peter Zijlstra]

On Thu, Feb 19, 2026 at 10:48:11PM +0800, Chen, Yu C wrote:
> 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.

I hadn't gotten that far yet. Still trying to read patch 4 :-)