Re: [RFC PATCH 0/3] Add Support for Multiple DC Regions

[Gregory Price <gourry@gourry.net>]

On Mon, Jan 12, 2026 at 02:50:01PM -0800, Anisa Su wrote:
> On Sat, Dec 13, 2025 at 12:36:24PM +0900, dan.j.williams@intel.com wrote:
> > Anisa Su wrote:
> > [..]
> > > > Unfortunately none of the details presented in this cover letter really
> > > > show why the kernel needs this additional complexity.
> > > > 
> > > > Can you go into more details on the use cases of multiple partitions?
> > > > 
> > > From what I understand, the motivation for DCD as a whole has always been a
> > > blocker for the entire series. However, this year we've seen multiple vendors
> > > demo memory pooling/sharing at SC,25[1], as well as the development of a 
> > > controller that supports "memory pooling and sharing across 
> > > multiple hosts" from Montage[2].
> > > 
> > > The flexibility and control provided by multiple partitions is
> > > an important capability of DCD for enabling composable memory 
> > > infrastructures. IMO, adding multi-partition support back in from v8 or
> > > picking up this patchset would strengthen the series.
> > 
> > Can you explain the use case for multiple partitions per-device?
> > Describe it in terms of what Linux loses if it never entertains this
> > aspect of the specification. It significantly complicates the ABI for a
> > benefit to Linux that I am unable to articulate.
> 
> Let me backtrack a bit here :( I was too hasty trying to push for
> multiple partitions.
> 
> However, can I ask for some clarification on what a sufficient use case is
> (with just a single partition)?
> 
> Then I'll (try my best) to demonstrate how this series can accomplish it
> so I can help land the single partition stuff first. Does that sound fair
> to you? Or am I misunderstanding the core problem?
> 
> Thanks,
> Anisa

regions != partitions

the discussion from today was regarding FAMFS wanting to balance over
subscription and max bandwidth - which requires a per-device region
and an interleaved regions, they cannot be managed with one region.

I can't think of a reason to need multiple *physical partitions* on
the device, when you can chop up a single partition with many regions.

Either way you need dedicated decoders for each region - regardless of
what partition it's on, so the extra partition doesn't get you much.

~Gregory