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

[Gregory Price]

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:
> > On Tue, 28 Jul 2026 11:13:48 +0530 Bharata B Rao <bharata@xxxxxxx> wrote:
> > 
> > > This patchset introduces pghot, a subsystem for hot page tracking and
> > > promotion.
> > 
> > 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.

~Gregory

[0] https://jovans2.github.io/files/vistara_camera_ready.pdf