Re: [PATCH v8 0/8] mm: Hot page tracking and promotion infrastructure

[David Hildenbrand (Arm)]

On 7/28/26 20:57, Gregory Price wrote:
> On Tue, Jul 28, 2026 at 07:24:46PM +0100, Matthew Wilcox wrote:
>> On Tue, Jul 28, 2026 at 11:14:01AM -0700, Andrew Morton wrote:
>>>
>>>
>>> Can DAMON be used to do this sort of thing adequately?
>>>
>>> Thanks, I'll await review input on this.
>>
>> I don't think we should do this.  I don't think it's a use-case that
>> customers actually want; I think it's something CPU vendors think their
>> customers want.  I've said this repeatedly over the months this patchset
>> has been in development.  I say no.
>>
> 
> I've been consistent about saying we (Meta) have been actively
> interested in this work and helping to drive the design of it.
> 
> So it's not simply something born out of a CPU vendor think tank,
> we're actively working on solving real problems with it.
> 
> I don't have data I can share now, but I think it's fair to wait
> for that data before faith-merging this on the hopes it's impactful.
> It does make it more difficult for us to do fleet-scale testing
> without it being upstream, but we'll get something.
> 
> Tiered memory is being deployed aggressively [0] for considerable
> value, and is here to stay - like it or not.

The diffstat is scary, to say the least. And the x86 stuff certainly needs x86
maintainer acks.

So far there is no real review -- we're in v8 without a single tag.

So this is far away from being mergeable.

I'm afraid this will need a lot more discussions, and likely RFC would have been
still appropriate at this point.

It's a shame this work was going on for quite a while without feedback (blame me
if you want :) but there are only so many hours in a day), but the main problem
is that this work in particular was not perceived to be high or even medium
priority so far.

-- 
Cheers,

David