Re: [PATCH v3 00/21] Cache Aware Scheduling

[Qais Yousef]

On 02/21/26 10:48, Chen, Yu C wrote:

> Leveraging push-lb for cache-aware task placement is interesting,
> and we have considered it during LPC when Vincent and Prateek presented it.
> It could be an enhancement to the basic cache-aware scheduling, IMO.
> Tim has mentioned that in
> https://lore.kernel.org/all/4514b6aef56d0ae144ebd56df9211c6599744633.camel@xxxxxxxxxxxxxxx/
> a bouncing issue needs to be resolved if task wakeup and push-lb are
> leveraged for cache-aware scheduling. They are very fast - so for
> cache-aware
> scheduling, it is possible that multiple invocations of
> select_idle_sibling()
> will find the same LLC suitable. Then multiple wakees are woken up on that
> LLC,
> causing over-aggregation. Later, when over-aggregation is detected, several
> tasks are migrated out of the LLC, which makes the LLC eligible again-and
> the
> pattern repeats back and forth.

I believe this is a symptom of how tagging is currently happening. I think if
we have more conservative tagging approach this will be less of a problem. But
proof is in the pudding as they say :-)