Re: [PATCH] mm/vmscan.c: only adjust related kswapd cpu affinity when online cpu

[Andrew Morton]

On Tue, 28 Jan 2020 08:39:42 +0800 Wei Yang <richardw.yang@xxxxxxxxxxxxxxx> wrote:

> >Is there ever a situation where the cpu to be onlined would have appeared 
> >in the cpumask of another node and so a different kswapd's cpumask would 
> >now include an off-node cpu?
> 
> No, I don't think so.
> 
> Per my understanding, kswapd_cpu_online() will be invoked when a cpu is
> onlined. And the particular cpu belongs to a particular numa node. So it is
> not necessary to iterate on every nodes.
> 
> And current code use cpumask_and_any() to do the check. If my understanding is
> correct, the check would return true if this node has any online cpu. This is
> likely to be true.
> 
> This is why I want to make the logic clear.

Please resend with a changelog which explains the above?