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

[Chen, Yu C]

On 2/15/2026 12:12 AM, Madadi Vineeth Reddy wrote:
> On 11/02/26 03:48, Tim Chen wrote:
> > From: Chen Yu <yu.c.chen@xxxxxxxxx>

[ ... ]

> According to this matrix (which I assume shows utilization after migration),
> G is expected for src=50% and dst=50%. However, the code performs the "both
> busy" check before adjusting src_util and dst_util:
>
> if (!fits_llc_capacity(dst_util, dst_cap) &&
>      !fits_llc_capacity(src_util, src_cap))
>      return mig_unrestricted;
>
> src_util = src_util - tsk_util;
> dst_util = dst_util + tsk_util;
>
> For example, with a 10% task migrating from src_util=60% to dst_util=40%:
>
> The check evaluates: !fits(40) && !fits(60) = false && true = false
> - Doesn't return mig_unrestricted
> - After adjustment: src=50%, dst=50%
> - Falls through to return mig_llc (Y)
>
> But the matrix indicates 50%/50% should be G, not Y.
>
> Moving this check after the utilization adjustment would make it consistent
> with the documented matrix.
Right, I previously considered only the snapshot of src/dst_util without
accounting for the migrating task. To keep this consistent with the 
decision
matrix, I will adjust the sequence as you suggested.

thanks,
Chenyu

> Thanks,
> Vineeth