Re: [RFC PATCH v2 0/5] mm/swap, memcg: Introduce swap tiers for cgroup based swap control

[YoungJun Park <youngjun.park@lge.com>]

On Wed, Feb 11, 2026 at 10:12:04PM -0800, Chris Li wrote:
> Hi Youngjun,
> 
> On Sun, Jan 25, 2026 at 10:53 PM Youngjun Park <youngjun.park@lge.com> wrote:
> >
> > This is the second version of the RFC for the "Swap Tiers" concept.
> > Link to v1: https://lore.kernel.org/linux-mm/20251109124947.1101520-1-youngjun.park@lge.com/
> >
> > This version incorporates feedback received during LPC 2025 and addresses
> > comments from the previous review. We have also included experimental
> > results based on usage scenarios intended for our internal platforms.
> 
> Thanks for the patches series.
> 
> Sorry for the late reply. I have been wanting to reply to it but get
> super busy at work.
> 
> Some high level feedback for the series. Now that you demonstrated the
> whole series, let's focus on making small mergiable baby steps. Just
> like the swap table has different phases. Make each step minimal, each
> step shows some value. Do the MVP, we can always add more features as
> a follow up step.
> 
> I suggest the first step is getting the tiers bits defined. Add only,
> no delete.  Get that reviewed and merged, then the next step is to use
> those tiers.
> 
> Chris

Hi Chris,

Thank you for the direction.

I agree that breaking the series into smaller, mergeable steps is the
right approach. However, since introducing the definitions alone might
lack immediate usage, I propose a slightly
modified roadmap to ensure Step 1 demonstrates some value.

Here is the plan I have in mind.

1. Swap Tier Definition & Addition
   - Introduce the concept, grouping logic, and the 'add' interface.
   - Value: Enables basic exception handling within the swap device
     itself using tiers.

2. Advanced Control (Delete/Modify)
   - Implement logic to remove or update tiers.
   - Value: Enhances the usability and management of the tiers
     established in Step 1.

3. External Integration (memcg, bpf etc ... )
   - Apply swap tiers for broader swap control.
   - Value: Connects swap tiers to other subsystems like memcg.

Does this roadmap look reasonable to you? I will proceed with preparing
the real patch series based on this structure.

Best regards,
Youngjun