Re: Cache-aware scheduling does not work well with amd big/little cores

[Tim Chen]

On Sun, 2026-09-27 at 12:47 +0200, Klaus Kusche wrote:
> Hello,
> 
> this one looks good.
> It does not show any core assignment anomalies 
> in the core bar graph (i.e. no processes are staying 
> on little cores when big cores are idle),
> and at least for the two compile jobs I tested,
> it gives timings which are 
> 
> * better w.r.t. elapsed wallclock time
> (sometimes slightly, sometimes significantly)
> than all other versions and patches I tried so far
> with cache-aware scheduling on
> 
> * and at least as good as the unpatched kernel
> with cache-aware scheduling turned off
> (so one does not loose anything by turning it on).

Thank you for testing and sharing the results so quickly.
I will send a cleaned up patch for sched/urgent branch shortly for
Peter.

Tim

> 
> As expected, the uv build profits more than the kernel built,
> because besides all-cores-loaded and single-core-loaded phases,
> it spends significant time with about half as many busy processes
> as cores, and in these phases, placement makes a difference.
> 
> Klaus Kusche
>