Re: [REGRESSION] [PATCH v3 7/7] sched/eevdf: Move to a single runqueue

[Mike Galbraith]

On Mon, 2026-09-28 at 11:12 +0800, Chen Yu wrote:
> 
> According to my test last week, stacking the waker and wakee on the same CPU brings
> a big improvement on my machine, iff the memory bandwidth is saturated. By comparison,
> if the memory bandwidth is low, stacking the wakee on top of the waker causes harm.

Ditto CPU wise.  The impact of even modest waker/wakee concurrency is
considerable.  For much of netperf, the post-wakeup tail becomes a CPU
service latency injection for the wakee when unnecessarily stacked. 
While cache misses sting, those hurt.

As box approaches saturation, stacking of somewhat synchronous stuff
becomes a better bet.  Aiming for having only waker's tail between
wakee and CPU has decent chance of being a winner in a box full of
wider obstacles.

	-Mike