Re: [RFC PATCH] mm: migrate: Add new node demotion strategy

[Huang, Ying]

Dave Hansen <dave.hansen@xxxxxxxxx> writes:

> On 11/4/21 2:13 AM, Baolin Wang wrote:
>> +What:		/sys/kernel/mm/numa/demotion_mode
>> +Date:		November 2021
>> +Contact:	Linux memory management mailing list <linux-mm@xxxxxxxxx>
>> +Description:	Set the demotion mode when enabling demoting pages during reclaim
>
> I don't think we need a tunable for this.  The existing behavior is just
> stupid for your hardware and can be replaced.

Yes.  I think so too.  I don't think DIRECT_DEMOTION is reasonable for your system.

> Let's also try to do it with the existing node_demotion[] data
> structure before we go adding more.

To avoid cache ping-pong, I guess some kind of per-CPU data structure
may be more suitable for interleaving among multiple nodes.

Best Regards,
Huang, Ying